1. Suppositories

2. Suppositories
A suppository is a medicated or non medicated solid dosage form generally intended for use in the rectum, vagina and urethra.
Drugs may be administered in suppository form for either local or systemic effects. Such action depends on the nature of the drug, its concentration, and the rate of absorption.
Emollients, astringents, antibacterial agents, steroids, and local
anesthetics are dispensed in suppository
for treating local conditions
Analgesics, antispasmodics, sed­atives,
tranquilizers, and antibacterial agents
are dispensed in suppository for systemic action

3. Types and shapes of suppositories
Rectal suppositories are tapered to resemble a torpedo shape. weigh about 2 g for adults and I g for Children.
2.Vaginal suppositories molded in the
globular or oviform shape, or compressed
on a tablet press into modified conical
shapes. weigh about 3 to 5 g.
3.Urethral suppositories called bougies, are
pencil shaped and pointed at one extremity.
for males weigh about 4 g each and are
100 to 150 mm long;
for females, they are 2 g each and usually
60 to 75 mm in length.

4. Factors Affecting Drug Absorption from
Rectal Suppositories
Physiologic Factors
Many drugs cannot be administered orally Why?
Affected by the digestive juices
Their therapeutic activity is modified by the liver
enzymes after absorption from the small intestine.

5. More than (50 to 70%) of rectally administered drugs can be absorbed from the ano­rectal area into the general circulation and still retain therapeutic values. Why?
The lower hemorrhoidal veins surrounding the colon
and rectum enter into the inferior vena cava and thus
bypass the liver. 1
The upper hemorrhoidal vein does
connect with the portal veins leading
to the liver.
The lymphatic circulation helps also
in absorbing a rectally administered
drug and in diverting the absorbed
drug from the liver.

6. The pH of the rectal mucosa has a rate-controlling role in drug absorption.2
The colon has a pH of ≈ 6.8, with no buffer
capacity, thus the dissolving drugs determine
the pH in the ano-rectal area.

7. Colonic lumen is permeable to the unionized forms of
drugs. Thus, weaker acids and bases are more readily
absorbed than the stronger, highly ionized ones. Thus,
the absorption of a drug would be enhanced by a change
in the pH of the rectal mucosa that would increase the
proportion of unionized drug.

8. So absorption of acidic drugs can be increased when
the pH of the surrounding fluids was lowered.
The absorption of salicylic acid rises from 12% at a pH
7 to 42% at pH 4. In contrast, with a basic drug like
quinine, which becomes more ionized at the lower pH
values, the absorption is decreased
from 20% at pH 7 to 9% at pH 4.

9. 3 The diffusion of the drug to the site on the
rectal mucosa at which absorption occurs. 3
The diffusivity is influenced by:
The nature of the medicament, such as the presence of
surfactant or the water-lipoidal solubility of the drug
The physiologic state of the colon (the amount and
chemical nature of the fluids and solids present).
The state of the anorectal membrane. This membranous
wall is covered with a relatively continuous mucous
blanket, which can act as a mechanical
barrier for the free passage of drug through
the pore space where absorption occurs.

10. Physicochemical Characteristics o f the Drug
Drug in vehicle- Drug in colon fluids-
Absorption through the rectal mucosa
drug absorption from the anorectal area
Release the drug from the suppository base.
Distribute by the surrounding fluids to sites of absorption
Dissolve in the fluids
Contact of the drug with the lumen walls, and to a large number of absorption sites.

11. Release the drug from the suppository base.
The lipid/water partition coefficient.
Solution of the drugs in solid water-soluble bases and oleaginous bases resulted in prolonged absorption times, because the drug is slowly eluted into the surrounding fluids.
For fatty bases from which the drug
is released as the vehicle melts, water-soluble oil-insoluble salts are preferred

12. For water-soluble bases from which the drug is
released as the vehicle dissolves, the water-soluble
type salt is the one of choice for quicker
drug absorption.
Ex. Ephedrine sulfate and quinine hydrochloride,
as well as sodium barbital and sodium salicylate,
are preferred than their bases and acids to increase
the absorption rate from suppositories.

13. The rate-limiting step in drug absorption from suppositories is the partitioning of the dissolved drug from the melted base and not the rate of solution of the drug in the body fluids.
The rate at which the drug diffuses to the surface of the suppository, the particle size of the suspended drug and the presence of surface active agents are factors that affect drug release from suppositories.
Solution of the drugs in solid polyethylene glycol and oleaginous bases resulted in prolonged absorption times, because the drug is slowly eluted into the surrounding fluids.

14. The particle size of the suspended drug
The larger the particle size, the slower the rate of solution. Thus, the drug absorption rate is decreased with an increase in drug particle size.

15. The concentration of the suspended drug
Marked increases in drug concentration play no role in altering drug absorption rates but drug concentration is related to release rates from suppository bases.

16. [surfactant­containing vehicle]
The presence of Surfactants in the formulation
[surfactant­containing vehicle]
Surfactants increase drug absorption rate due to:
Surface tension lowering
The mucus-peptizing action
The rectal membrane is covered by a continuous mucous blanket, which may be washed away by colonic fluids that have reduced surface tension. The cleansing action caused by the surfactant­containing vehicle may make additional pore spaces available for drug absorption, thus facilitating drug movement across the rectal membrane barrier.

17. Ex. in the case of sodium iodide, absorption is accelerated in the presence of surfactants and be proportional to the relative surface tension lowering of the vehicle.
N.B. In the case of phenol-type drugs, absorption rate is decreased in the presence of surfactant, due to the formation of a drug-surfactant complex.

18. 2. Absorption from the lumen walls
The anorectal and colonic mucosae are selectively permeable to the uncharged drug molecule. Thus, lipid-soluble undissociated drug is the most readily absorbed form.
Completely ionized drugs like quaternary ammonium
compounds and sulfonic acid derivatives are poorly
absorbed.
Unionized substances that are lipid-insoluble are poorly
Thus, drug absorption can be increased by the use of buffer solutions or salts that convert the pH of the anorectal area to a value that increases the concentration of unionized drug.

19. Physicochemical Characteristics of the Base
For Fatty Bases:
The absorption rate is faster from fatty bases having a lower melting range than from those with higher melting ranges
Since fatty bases may harden for several months after molding, this rise in melting range certainly would affect absorption
For Polyethylene Glycol Bases
The absorption rate increases along with hydroxyl values.
The absorption rate is faster as the molecular mass of the polyethylene glycols (PEGs) used increased.

20. Adjuvants Changes in the rheological properties
of the base at body temperature
Drug release from hvdrogels of hydropolyethyl
methacrylate decreased as increasing percentages of the cross-linking agent ethylene glycol dimethacrylate.
Addition of hydrophobic colloidal silicon oxide to fat base Suppositories dramatically changes the rheologic behavior of the mass.

21. 2. Affecting the dissolution of the drug in the media of the dosage form.
In emulsion type bases. the amount of water-soluble drug released increased with the water content of the base, and that the rate of drug released could be prolonged by the addition of an aqueous polymer.
Salicylates improve the rectal absorption of water-soluble antibiotics in lipophilic bases.

22. Specifications for suppository bases
Origin and Chemical Composition.
A brief description of the composition of the base reveals the source of origin (i.e., either entirely natural, synthetic or modified natural products).
Physical or chemical incompatibilities of the base with the other constituents may be pre­dicted if the exact formula composition is known, including preservatives, antioxidants and emulsifiers.

23. 2. Melting Range.
Since fatty suppository bases are complex mixtures of triglycerides and therefore do not have sharp melting points, their melting
characteristics are expressed as a range indicating the temperature at which the fat starts to melt and the temperature at which it is completely melted.

24. 3. Solid-Fat Index (SFI).
A base with a sharp drop in solids over a short temperature span proves brittle if molded too quickly. This type of base requires a reduced differential between mold temperature and mass temperature for trouble-free molding. Suppository hardness can be determined by the solids content at room temperature. Since skin temperature is about 32°C, one can predict a product that would be dry to touch from a solids content over 30% at that temperature.

25. 4. Hydroxyl Value.
This is a measure of unesterified positions on glyceride molecules and reflects the monoglyceride and diglyceride content of a fatty base. The number represents the milligrams of KOH that would neutralize the acetic acid used to acetylate 1 g of fat.

26. 5. Solidification Point.
Is the time required for solidifying the base when it is chilled in the mold. If the interval between the melting range and solidification point is 10°C or more, the time required for solidification may have to be shortened by refrigeration to produce a more efficient manufacturing procedure.

27. 6. Saponification Value.
Is the number of milligrams of potassium hydroxide required to neutralize the free acids and saponify the esters contained in 1 g of a fat is an indication of the type (mono-, di-, or tri-) glyceride, as well as the amount of glyceride present.

28. 7. Iodine Value. Is the number of grams of iodine that
reacts with 100 g of fat or other unsaturated material. The possibility of decomposition by moisture, acids, and oxygen (which leads to rancidity in fats) increases with high iodine values.

29. 8. Water Number. 9. Acid Value.
Is the amount of water, in grams, that can be incorporated in 100 g of fat.
The "water number" can be increased by the addition of surface active agents, monoglycerides, and other emulsifiers.
9. Acid Value.
Is the number of milligrams of potassium hydroxide required to neutralize the free acid in 1 g of substance. Low "acid values" or complete absence of acid are important for good suppository bases.
Free acids complicate formulation work, because they react with other ingredients and can also cause irritation when in contact with mucous membranes.

30. Types of Suppository Bases
The Ideal Suppository Base for long shelf-life
Having reached equilibrium crystallinity.
The majority of components melt at rectal
temperature 36°C
Bases with higher melting ranges may be employed for:
eutectic mixtures, addition of oils, balsams, and
suppositories intended for use in tropical climates.

31. 2. Completely nontoxic and nonirritating to sensitive
and inflamed tissues.
3. Compatible with a broad variety of drugs.
4. Has no metastable forms.
5. Shrinks sufficiently on cooling to release itself
from the mold without the need for mold
lubricants.

32. 6. Has wetting and emulsifying properties.
7. High water number.
i.e. a high percentage of water can be incorporated in it.
8. Stable on storage.
i.e. does not change color, odor, or drug release pattern.
9. Can be manufactured by molding by either hand,
machine, compression, or extrusion.

33. If the base is fatty, it has the following additional requirements:
10. Acid value below 3
11. Saponification value ranges from 200 to 245
12. Iodine value less than 7
13. The interval between "melting point (34oC)" and
"solidification (32oC) point" is small

34. 14. Low melting ranges (30- 34oC) for incorporating drugs
that increases the melting range of the base.
Ex. Silver nitrate or lead acetate
High melting ranges (37-41°C) for incorporating drugs
that lower melting points of the base.
Ex. Camphor, chloral hydrate, menthol, phenol, thymol,
and several types of volatile oils or for formulating
suppositories for use in tropical climates.

35. Oleogenous Suppository Bases
Cocoa Butter (Theobroma Oil)
Cocoa butter is a yellowish­white, solid, brittle fat.
Smells and tastes like chocolate.
Its melting point lies between 30°C and 35°C.
Its iodine value is between 34 and 38.
Its acid value is no higher than 4.

36.     The most widely used suppository base
ADVANTAGES of CACAO BUTTER as SUPPOSITORY BASE
The most widely used suppository base
It satisfies many of the requirements for an ideal base
Safe, non reactive and melts at
body temperature.   

37.  DISADVANTAGES of CACAO BUTTER as SUPPOSITORY BASE
Cocoa butter does not contain emulsifiers and
therefore does not take up large quantities of
water (maximum 20 to 30 g of water to 100 g
of cocoa butter).
The addition of emulsifiers such as Tween 60 (5 to 10%) increases the water absorption considerably. Emulsifiers also help to keep insoluble substances suspended in the fat. Suspension stability is further obtained by the addition of materials (aluminum monostearate, silica) that give melted fats thixotropic properties. There is always the possibility that the suppositories containing these additives will harden on storage. Therefore, prolonged, careful stability observations are recommended.

38. Low contractility during solidification causes the suppositories to adhere to molds and necessitates the use of mold release agents or lubricants. 
Drugs as volatile oils, creosote, phenol, and chloral hydrate lower the melting point of cocoa butter.
To correct this condition, wax and spermaceti are commonly used. 

39.  Cacao butter exhibits different polymorphisms each
has different melting points
Cocoa butter is primarily a triglyceride.
A phenomenon due to the high proportion of unsaturated triglycerides is that it exhibits polymorphism (the property of existing in different crystalline forms).
Each of the different forms of cocoa butter has different melting points, and different drug release rates.
When cocoa butter is heated above its melting temperature (36°C) and chilled to its solidification point (below 15°C), immediately after returning to room temperature this cocoa butter has a melting point of about 24°C, approximately 12° below its original state.

40. Cocoa butter is thought to be capable of existing in four crystalline states:
The α form
Obtained by suddenly cooling melted cocoa butter to 0°C.
It melts at 24°C
2. The β’ form
Crystallizes out of the liquefied cocoa butter with stirring
at 18 to 23°C.
Its melting between 28 and 31°C.
3. The β’ form
Changes slowly into the stable β form which melts
between 34 and 35°C.
This change is accompanied by a volume contraction.
4. The γ form
Melting at 18°C
Obtained by pouring a cool (20°C) cocoa butter, before it
solidifies, into a container which is cooled at deep­freeze
temperature.

41. The formation of various forms of cocoa butter depends on:
The degree of heating
The cooling process
The conditions during this process.
At temperatures below 36°C, negligible amounts of the
unstable forms are obtained
But prolonged heat above that critical temperature causes
the formation of the unstable crystals with resulting
lowered melting points. Thus, prolonged heating in the
process of melting the fats must be avoided
The reconversion to the stable β form takes one to four
days, depending on the storage temperature, the higher the
temperature, the faster the change.

42. The formation of the unstable forms can be avoided by:
If the mass is not completely melted, the remaining
crystals prevent the formation of the unstable form.
Small amounts of stable crystals added to the melted
cocoa butter accelerate the change from the unstable to
the stable form; this process is called “Seeding."
The solidified melt is tempered at temperatures between
28 and 32oC for hours or days, causing a comparatively
quick Change from the unstable to the stable form.

43. Cocoa Butter Substitutes
Cocoa butter substitutes maintain the desirable properties of cocoa butter and eliminate the undesirable ones.
Treatment of Vegetable Oils to Produce Suppository Bases
Synthetic or natural oils as vegetable oils as coconut or palm kernel oil are modified by:
Esterification, hydrogenation and fractionation at different melting ranges to obtain the desired product.

44. Hydrogenation It is an inexpensive method
Hydrogenation of oil as corn oil to reduce the unsaturation
and so increase the percentage of solid triglycerides at
room temperature.
The triglycerides with lower melting points are removed by
solvent extraction or by pressing.
This type of fat products are referred to as "hard butter."

45. Interesterification
Interesterification of oils as coconut oil, palm kernel oil,
and/or palm oil (all chosen for their high content of lauric
acid moieties) are refined to remove free fatty acids,
deodorized to remove volatiles, hydrogenated as
described previously, and then interesterified.
This final step, catalyzed by sodium methoxide, more
equally distributes the fatty acid moieties among the
glycerin molecules, creating more common triglycerides,
and therefore a more narrow melting range.

46. Re-esterification
First, the oil is split into fatty acids and glycerin by treatment with high-pressure steam.
The glycerin is removed from the mixture, and the remaining free fatty acids consist of C6-C18 chain length compounds are (caproic, caprylic, capric, lauric, myristic, palmitic, oleic, and stearic acids).
Caproic, caprylic, and capric acids are removed by fractional vacuum distillation, because they are readily rancidified and may cause irritation of mucous membranes.
The remaining fatty acids, consisting mainly of lauric acid, are hydrogenated to harden the mixture and lower its iodine value.

47. Hydrophilic Suppository Bases
Glycerin Suppositories
Glycerinated gelatin suppositories do not melt at body temperature but dissolve in the secretions of the body cavity in which they are inserted (vaginal or rectal).
Solution time is regulated by the proportion of gelatin/glycerin/water used, the nature of the gelatin used, and the chemical reaction of the drug with gelatin.
Glycerinated gelatin suppositories support mold or bacterial growth, thus, they are stored in a cool place and often contain agents that inhibit microbial growth.
Because glycerin is hygroscopic, these suppositories are packaged in materials that protect them from environmental moisture.

48. The Polyethylene Glycols (Carbowax and Polyglycols)
Long-chain polymers of ethylene oxide have the general formula HOCH2 (CH2OCH2)X CH2OH
When their average molecular weight ranges from 200 to
600 they exist as liquids, and as wax-like solids when
their molecular weights are above 1000.
Their water solubility, hygroscopicity, and vapor pressure
decrease with increasing average molecular weights.
The wide range of melting points and solubilities makes
possible to formulate suppositories with various degrees
of heat stability and different dissolution rates.

49. Several combinations of polyethylene glycols have been prepared for suppository bases having different physical characteristics.
Base 1
Polyethylene glycol %
Polyethylene glycol %
This base has low-melting and require refrigeration.
It is useful when rapid disintegration is desired.
Base 2
Polyethylene glycol %
Polyethylene glycol %
More heat stable than Base 1 and stored at higher temperatures.
It is useful when a slow release of active ingredients is desired.

50. ADVANTAGES of POLYETHYLENE GLYCOL
as SUPPOSITORY BASE
Polyethylene glycol suppositories do not require a mold lubricant and are easier to prepare than cocoa butter suppositories.
They are physiologically inert, do not hydrolyze or deteriorate and do not support mold growth.  

51. DISADVANTAGES of POLYETHYLENE GLYCOL
as SUPPOSITORY BASE
Most patients do not feel discomfort from the use of these suppositories, because this type of Bases cause irritation "sting“ to mucous membranes when water drawn from the mucosa. This irritation may be eliminated by dipping in water before insertion or by addition of 10% water to facilitate solution of the suppository after insertion. 

52. 
The polyethylene glycol suppositories cannot be prepared by hand rolling but prepared by both molding and cold compression methods.
Special precautions are necessary in preparing a molded suppository with the polyethylene glycol bases.
The mold must be dry because the base is soluble in water.
The suppository will be fissured owing to the
crystallization and contraction of the polymer. Such
suppositories may be easily fractured in packaging or
handling. To solve this problem the melted mass must be
allowed to cool to the congealing point before pouring.

53. Water-Dispersible Bases
These are nonionic surface active materials, related chemically to the polyethylene glycols.
The surfactants most commonly used in suppository formulations are the polyoxyethylene sorbitan fatty acid esters (Tween), the polyoxyethylene stearates (Myrj) and the sorbitan fatty acid esters (Span and Arlacel). These surface active agents may be used alone, blended, or used in combination with other suppository vehicle materials to yield a wide range of melting points and consistencies.

54. ADVANTAGES of WATER-DISPERIBLE BASES as SUPPOSITORY BASE
Can be used for formulating both water-soluble and oil-
soluble drugs.
Can be stored and handed at elevated temperatures
Have broad drug compatibility.
Nonsupport of microbial growth, nontoxic and not cause
sensitivity.    

55. DISADVANTAGES of WATER-DISPERIBLE BASES as SUPPOSITORY BASE
Caution must be taken in the use of surfactants with drugs
due to the increase in the rate of drug absorption.
These surface active agents can show interaction with
drugs and a consequent decrease in therapeutic effects.  

56. Compressed Tablet Suppositories
Rectal suppositories usually are not compressed as tablets, because the amount of liquid in the rectal cavity is insufficient for tablet disintegration.
Effervescent tablets aid disintegration, as carbon dioxide releasing laxative suppositories.
This compressed rectal suppository is coated
with water-soluble polyethylene glycol to aid
in insertion into the rectum.

57. The suppositories are non-melting, but dissolve in body fluids.
The compressed tablet for vaginal use weighing about 3 g with almond shape to ease insertion. The moisture level of the vagina is sufficient for disintegration and dissolution.
A typical vaginal tablet contains active ingredients, with boric and/or phosphoric acid for adjusting the acidity of the vagina to pH 5. Vaginal suppositories are usually used for systemic or topical therapy, as in the treatment of vaginitis, or as a spermatocide.
Soft gelatin capsules filled with liquid or solid drugs used for vaginal use.
The suppositories are non-melting,
but dissolve in body fluids.

58. Unusual Types of Suppositories
Layered suppository has an outer shell with 37 to 38°C melting point and a core with 34 to 35°C melting point. This is prepared by dipping the suppository in the coating solution until the desired coating thickness is obtained. Each layer contains different drugs or used to prevent coalescing of adjacent suppositories during storage.

59. The layering also may be multilayering in the horizontal plane
The layering also may be multilayering in the horizontal plane. This is prepared by partially filling the mold, allowing the mass to congeal, and pouring additional layers. Multilayered suppositories used for separating incompatible drugs in different layers and providing different melting characteristics for controlling the rate of drug absorption.

60. Problems in Formulating Suppositories
Formulation of Suppositories
Problems in Formulating Suppositories
Hygroscopicity
Glycerinated gelatin suppositories are hygroscopic, they lose moisture by evaporation in dry climates and absorb moisture under conditions of high humidity.
Polyethylene glycol bases are hygroscopic, the rate of moisture change in polyethylene glycol bases depends on humidity, temperature and on the chain length of the molecule. As the molecular weight increases, the hygroscopicity decreases.

61. Water in Suppositories
Use of water as a solvent for incorporating substances in suppository bases should be avoided for the following reasons.
1. Water accelerates the oxidation of fats.
2. If the water evaporates, the dissolved substances
would crystallize out.
3. Reactions between ingredients are more likely to occur
in the presence of water.
4. Bacterial or fungal growth necessitates the addition of
bacteriostatic agents as parabens.

62. Incompatibilities Polyethylene glycol are incompatible with
silver salts,
tannic acid, aminopyrine, quinine, ichthammol, aspirin,
benzocaine, iodochlorhydroxyquin, and sulfonamides.
Many chemicals have a tendency to crystallize out of
polyethylene glycol, e.g. sodium barbital, salicylic acid,
and camphor.
Higher concentrations of salicylic acid soften polyethylene
glycol to an ointment-like consistency, and aspirin
complexes with it.
Penicillin G, although stable in cocoa butter and other
fatty bases, decomposes in polyethylene glycol bases.
Fatty bases with significant hydroxyl values may react
with acidic ingredients.

63. Viscosity
The viscosity of the melted suppository mass is important in the manufacture of the suppository and to its behavior in the rectum after melting.
Melted cocoa butter and some of its substitutes have low viscosities, whereas the glycerinated gelatin and polyethylene glycol type base have viscosities considerably higher than cocoa butter.

64. In the manufacture of suppositories made with low-viscosity bases, extra care must be exercised to avoid the sedimentation of suspended particles. Poor technique can lead to nonuniform suppositories, particularly in the distribution of active ingredients.
To prevent segregation of particles suspended in molten bases, the well-mixed mass should be handled at the lowest temperature necessary to maintain fluidity, constantly stirred without entrapping air, and quickly solidified in the mold.

65. The following approaches may be taken to overcome the
problems caused by use of low viscosity bases.
1. Use a base with a more narrow melting range that is
closer to body temperature.
2.The inclusion of approximately 2% aluminum monostearate not only increases the viscosity of the fat base considerably, but also aids in maintaining a homogeneous suspension of insoluble materials. Cetyl, stearyl, or myristyl alcohols or stearic acid are added to improve the consistency of suppositories.

66. Brittleness Suppositories made from cocoa butter are elastic and do
not fracture.
Synthetic fatty bases with a high degree of hydrogenation
are more brittle. Fracturing of the suppository made with
such bases is induced by rapid chilling (shock cooling) of
the melted bases in an extremely cold mold.
Brittle suppositories have problems in manufacturing,
handling and wrapping.
To overcome this difficulty, the temperature differential between melted base and mold should be as small as possible. Addition of a small amount of Tween 80, Tween 85, fatty acid monoglycerides, castor oil, glycerin, or propylene glycol increases its plasticity and renders it less brittle.

67. Density To calculate the amount of drug per suppository,
the density of the base must be known.
The volume of the mold cavity is fixed, and therefore, the weight of the individual suppository depends on the density of the mass.
Knowledge of the suppository weight can be obtained from a given mold and density of the chosen base; the active ingredients can then be added to the bulk base in such an amount that the exact quantity of drug is present in each molded suppository.

68. If volume contraction occurs in the mold
during cooling, additional compensation
must be made to obtain the proper suppository weight.
Thus, density alone cannot be the sole criterion for calculating suppository weight per fixed volume mold.
When volume contraction occurs, the suppository weight is determined empirically by small batch runs.

69. Volume Contraction This phenomenon occurs in many melted
suppository bases after cooling in the mold.
The results are manifested in the following two ways.
1. Good mold release. This is caused by the mass pulling away from the sides of the mold. This contraction facilitates the removal of the suppositories from the mold, eliminating the need for mold release agents.

70. 2. Contraction hole formation at the open end of the mold
2. Contraction hole formation at the open end of the mold. This undesirable feature results in lowered suppository weight and imperfect appearance of the suppository.
The contraction can be eliminated by pouring a mass slightly above its congealing temperature into a mold warmed to about the same temperature. In volume production using standard molds, where adequate control of temperature may not be feasible, the mold is overfilled so that the excess mass containing the contraction hole can be scraped off.

71. Lubricants or Mold Release Agents
Cocoa butter adheres to suppository
molds because of its low volume contraction.
These suppositories are difficult to remove from the molds, and various mold lubricants or release agents must be used to overcome this difficulty.
Mineral oil, an aqueous solution of sodium lauryl sulfate, various silicones, alcohol, and tincture of green soap are examples of agents employed for this purpose.
They are applied by wiping, brushing, or spraying. The release of suppositories from damaged molds was improved by coating the cavities with polytetra­fluoroethylene (Teflon).

72. Dosage Replacement Factor
The amount of base that is replaced by active ingredients in the suppository formulation can be calculated.
The replacement factor, f, is derived from the following equation:
where: E = weight of pure base suppositories
G = weight of suppositories with X% active ingredient
f = 100 (E - G) + 1
(G)(X)

73. Weight and Volume Control
The amount of active ingredient in each suppository depends on:
Its concentration in the mass;
The volume of the mold cavity;
The specific gravity of the base;
The volume variation between molds, good machining of
the molds should keep the volume of each cavity within
2% of a desired value;
Weight variations between suppositories due to the
inconsistencies in the manufacturing process,
e.g., incomplete closing of molds, uneven scrapings.
Regardless of the reason for the variation in weight, it
should be within ±5%.

74. The German and Russian Pharmacopeias state individual weight variations of rectal suppositories at ±5% of the average weight.
The Pharmacopeia Nordica allows ± 10% of the average weight for 90% of the suppositories, but these deviations must not exceed ±20%.

75. Rancidity and Antioxidants
Confusion may take place between the acidity of fats with rancidity.
The presence of free fatty acids is no indication of rancidity or that such a product may become rancid.
Rancidity results from the autoxidation and decomposition of unsaturated fats into low and medium molecular weight
saturated and unsaturated aldehydes, ketones and acids, which have strong, unpleasant odors.

76. The lower the content of unsaturated fatty acid constituents in a suppository base, the greater is its resistance to rancidity.
Since this reaction begins with the formation of hydroperoxides, the measure of autoxidation is the peroxide value (active oxygen) which is a measure of the iodine liberated from an acidified solution of potassium iodide by "peroxide oxygen" of the fats.

77. Examples of effective antioxidants:
Phenols: such as m- or p-diphenols; α-naphthol;
Quinones: such as hydroquinone or β-naphthoquinone;
Tocopherols: particularly the α and β forms;
Gossypol present in cottonseed oil;
Sesamol present in sesame oil;
Propyl gallate and gallic acid;
Tannins and tannic acid;
Ascorbic acid and its esters;
Butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT).

78. An Approach in Formulating Suppositories
The important considerations of the formulator are:
Is the medication intended for local or systemic use?
Is the site of application rectal, vaginal or urethral?
Is the desired effect to be quick or slow and prolonged?

79. Preliminary suppository bases to be studied are first
evaluated by measuring drug availability from the
suppository in water at 36 to 37°C.
Availability and cost of the suppository bases
Stability of both active ingredients and base at 4°C and
room temperature.
Ease of molding and release in the manufacturing
equipment.
Toxicity (irritancy) and drug availability are measured in
animals before the medication is ready for human
clinical trials.

80. Suppositories for Systemic Effect
The drug should be homogeneously dispersible
in base used it, but releasable at the desired rate to the aqueous body fluids surrounding the suppository.
Therefore, the solubility of the active ingredient in water or other solvents should be known.
If the drug favors water, a fatty base with low water number may be preferred.
On the other hand, if the drug is highly fat-soluble, a water-type base, with the addition of a surfactant to enhance solubility may be the preferred choice.

81. To enhance the homogeneity of drug in the desired base, either a suitable solvent is used or the drug is finely ground before incorporation.
A drug that is soluble in a minimal quantity of water, or in another liquid miscible with the base, can be dissolved and the solution added to the molten base.
If the drug is to be incorporated directly into the base, it should be finely ground so that 100% can be passed through a 100-mesh USP screen.
Fragility, brittleness tests must be performed.

82. The theoretically desirable suppository formulations are molded in the laboratory and stored at room temperature (25 ± 3°C) for at least 48 hours before in vitro testing for release rate.
In-vitro release rates as a quality control procedure and the suppository formulation chosen yields the in vitro release rate pattern that is to be used as the desired standard.
Chemical and physical stability, consistency of in vitro drug release patterns within theoretically desired ranges, and animal toxicity are some characteristics studied before suppository formulas are chosen for human clinical trials.

83. The suppositories are stored at room temperature (25 ± 3°C) and at 4°C for prolonged stability tests. They are tested at regular intervals (1- ,3-, and 6-month and 1- and 2-year periods) for changes in appearance, melting and softening range, drug stability, base stability, and in vitro drug release pattern.
In vivo clinical findings in man are the last criteria for choosing a desired formulation. The clinical findings may be based on blood levels of the drug and/or desired clinical effects in man.

84. Suppositories for Local Effect
Drugs intended for local action are generally non-absorbable, e.g., drugs for hemorrhoids, local anesthetics, and antiseptics.
The bases used for these drugs are virtually non-absorbable, slow in melting, and slow in drug release, as contrasted with suppository bases intended for systemic drugs.
Local effects are generally delivered within
a half hour and last at least 4 hours.

85. The desired base should release an adequate amount of drug within a half hour, and completely melt with release of all drug between 4 and 6 hours. A suppository that does not melt within the 6-hour test period would probably not completely release its drug, cause discomfort to the patient and be expelled by the patient before it is fully utilized.
Tests in animals must show no irritancy if the suppository is to be used in man.

86. Manufacture of Suppositories
Three methods are used in preparing suppositories:
Molding by hand
Compression molding
Pour molding

87. Hand Molding
The simplest and oldest method of preparing a suppository is by hand, i.e. by rolling the well­blended suppository base containing the active ingredients into a cylindrical rod of desired length and diameter, or into vaginal balls of the intended weight.
Starch or talc powder on the rolling surface
and hands prevent the mass from adhering.
The rod is cut into portions, and one end is pointed.
This method is practical and economical for the manufacture of small numbers of suppositories.

88. Compression Molding A more uniform and pharmaceutically elegant
suppository can be made by compressing the cold
mass into a desired shape.
A hand­turned wheel pushes a piston against the
suppository mass contained in a cylinder, so that the
mass is extruded into molds (usually three).

89. Advantages over hand molding method:
It avoids the possibilities of sedimentation of the insoluble solids in the suppository base
Disadvantages:
Too slow for large-scale production.
Molding fat type base suppositories is air entrapment.
This makes close weight control impossible and also
favors the possible oxidation of both the base and
active ingredients.

90. Pour Molding The most commonly used method for producing
suppositories on both a small and a large scale.
First, the base material is melted, preferably on a water or
steam bath to avoid local overheating
Then the active ingredients are either emulsified or
suspended in it.
Finally, the mass is poured into cooled metal molds, which
are usually chrome or nickel-plated.

91. Preparation

93. Packaging of Molded Suppositories
Suppositories must be packaged so that each suppository is overwrapped, or they must be placed in a container in that they do not touch each other.
Suppositories usually are foiled in tin,
aluminum, paper and plastic strips.

94. Poorly wrapped and packaged suppositories can cause:
Staining, breakage, or deformation by melting caused by adhesion.
Suppositories in direct contact with one another are spoiled by fusion resulting from changes in temperature. Partially melted suppositories stain the outer package unless they are overwrapped or are packaged with some other barrier that prevents contact with the outer container.

95. In-Package Molding Suppositories
It is a method for molding suppositories directly in their wrapping material either plastic or aluminum foil.
The tops of the molds are left open for the entrance of filling nozzles. After the mass has been injected, the tops are sealed.
The strips are then passed in an upright position through a cooling station.

96.     The advantages of in-package molding:
High production rates.
No bulk handling or storage of un­wrapped suppositories.
Disposable molds have the additional advantage of being suited for suppositories intended for tropical climates. If the mass should melt at the high storage temperatures, the mold still retains its proper shape, so that upon cooling it can be dispensed without deformation.
The disadvantages of in-package molding:
Dependence on the shape of the formed mold    