1. Ointments and Creams

2. Definition
OINTMENTS
Ointments are semisolid preparations intended for topical application. They are used to provide protective and emollient effects on the skin or carry medicaments for treating certain topical ailments. They are also used to deliver drugs into eye, nose, vagina, and rectum.
Ointments intended for ophthalmic purposes are required to be sterile. When applied to the eyes, they reside in the conjunctival sac for prolonged periods compared to solutions and suspensions and improve the fraction of drug absorbed across ocular tissues.
Ointments are absorbed slowly from the site of application.

3. CREAMS
Creams are basically ointments which are made less greasy by incorporation of water. Presence of water in creams makes them act as emulsions and therefore are sometimes referred as semisolid emulsions.
Hydrophilic creams contain large amounts of water in their external phase (e.g., vanishing cream) and hydrophobic creams contain water in the internal phase (e.g., cold cream).
As ointments, creams are formulated to provide protective, emollient actions or deliver drugs to surface or interior layers of skin, rectum, and vagina. Creams are softer than ointments and are preferred because of their easy removal from containers and good spreadability over the absorption site.
Drugs from creams are absorbed rapidly from the site of application.

4. The main rule of the local therapy is: if the skin is dry, use an ointment;
if it is wet, use a cream.

5. Bases
An ideal ointment base should have following physicochemical properties:
Stability
Neutral in reaction
Non greasy
Non degreasing
Non irritating
Nondehydrating
Non hygroscopic
Water removable
Compatible with all medicaments
Free from odors
Nonstaining
Efficient on all skin type
Composed of readily available component of known chemical composition
Melting & softening at body temperature

6. Capable of holding 50% of water
Easily compounded
Smoothness
ease of application
Suitable base
Properly distributed medicament

7. Ointment Bases Classification
ACCORDING TO PENETRATION:
1.EPIDERMIC OINTMENT :
Slight penetration power
Therapeutic effect on diseased epithelium
e.g,petrolatum,waxes and 1+2.
2.ENDODERMIC OINTMENT:
Power of deeper penetration
e.g,vegi oils,lards,lanolin and 1+2+3
3.DIADERMIC OINTMENT:
Penetrate skin effectively. better absorption
e.g., emulsion type & water soluble.

8. PHYSICAL CLASSIFICATION
They may be classified into four main groups:
Hydrocarbon Bases
Absorption Bases
Emulsion Bases
Water Miscible /Soluble Bases

9. HYDROCARBON BASES:
Hydrocarbon bases are made of oleaginous materials. They provide emollient and protective properties and remain in the skin for prolonged periods. It is difficult to incorporate aqueous phases into hydrocarbon bases. However, powders can be incorporated into these bases with the aid of liquid petrolatum.
(a)  Properties.
1.Anhydrous
2.Do not absorb water readily (Hydrophobic)
3. Insoluble in water
4.Not washable
(b) Examples. Fats and fixed oils such as lard, olive oil, cottonseed oil, petrolatum(soft paraffin), white ointment, Yellow Ointment (Bees Wax) and silicon bases.
(c) Advantages. Highly compatible; occlusive; good emollients.
(d)  Disadvantages. Difficult to remove from skin and clothing; May go rancid . allergies

10. ABSORPTION BASES:
Absorption bases contain small amounts of water. They provide relatively less emollient properties than hydrocarbon bases. Similar to hydrocarbon bases, absorption bases are also difficult to remove from the skin due to their hydrophobic nature.
(a)Properties.
Anhydrous
will absorb water( hydrophillic)
Insoluble in water
most are not washable.
(b)Example. Hydrophilic Petrolatum, USP; Anhydrous Lanolin, USP.
(c)  Advantages. Highly compatible; relatively stable to heat; can be used in anhydrous form or water can be added when emolliency is desired.
(d)Disadvantage. Greasy. Less occlusive.

11. EMULSION BASES (Water Removable):
A. Emulsion Ointment Base (W/O):
1. Hydrous
2. Will absorb water
3. Insoluble in water
4. Not washable
5. Water-Oil-Emulsion
6. Examples—Lanolin, Rose water Ointment, Cold Cream
B. Emulsion Ointment Base (O/W):
4. Washable
5. Oil-in-Water Emulsion
6. Examples; Hydrophilic Ointment, PEG Ointment

12. Advantages:
Washable and nongreasy if oil-in-water (o/w).
Disadvantages:
Subject to water loss if o/w, greasy and unwashable if water-in-oil (w/o), unless, a preservative is added, the emulsion bases are subject to mold growth.

13. Water Miscible /Soluble Bases
Water soluble bases do not contain any oily or oleaginous phase. Solids can be easily incorporated into these bases. They may be completely removed from the skin due to their water solubility. Polyethylene glycol (PEG) ointment National Formulary (NF) is an example of a water - soluble base.
The polyethylene glycol polymers, or Carbowaxes, are of great importance in ointments.
The names of the Carbowaxes include numbers that roughly indicate their average molecular weight.
Carbowaxes with a molecular weight in the area of 1,000 are soft, ointment-like substances.
As the molecular weight increases, they become harder and they finally become waxes. They are water-soluble, nonvolatile, and do not deteriorate or support mold growth.

14. Properties:
Anhydrous
Will absorb water and dissolve in water
Washable
Non-greasy.
Examples. Carbowax compounds such as the polyethylene glycol bases containing pectin, cellulose, Bentonite, and gelatin.

15. Advantages.
Wide range of compatibility;
do not become rancid or support microbial growth;
nonirritating (to the same degree as lanolin, petrolatum, etc);
adhere well to skin;
easily washed off;
low incidence of sensitization.
Disadvantages.
Sometimes undergo gradual discoloration with certain drugs.
Unless cetyl alcohol is added, an aqueous solution can be added only to the extent of 5 percent.

16. LANE & BLANK CLASSIFICATION:
According to physicochemical action of vehicle on skin:
VEHICLE ACTED AS AQEOUS MIXTURE
VEHICLE ACTED AS OILS
VEHICLE ACTED AS POWDERS
VEHICLE ACTED AS ORGANIC SOLVENT

17. CHEMICAL CLASSIFICATION:
Hydrocarbon
Alcohol
Acid
Ester
Soaps
Miscellaneous

18. ACCORDING TO USES OR THERAPEUTIC
Emollient
Protective
Anti Infectives
Anti Eczematic
Keratolytic
Anti Prespirants
Anti Sebhorrics

19. Selection of the Appropriate Base Based on:
Desired release rate.
Desirability for enhancement of percutaneous absorption.
Advisability of occlusion.
Short-term or long-term stability.
Influence of drug on consistency or other features of ointment base.
Patient factor - dry or weeping (oozing) skin.

20. METHOD OF PREPARATION
MIXING BY FUSION:
In this method, the ingredients are melted together and stirred to ensure homogeneity.
On a small scale, fusion is usually carried out in an evaporating basin made of glazed porcelain or stainless steel over a water bath.
The constituents of the base are melted together in the basin and stirred gently after melting until cool.
Vigorous stirring can cause aeration which should be avoided.
Any foreign particles that are naked on melting cam be removed by decantation or by using a warm muslin cloth.
If product is granular after cooling due to separation of some ingredients of high MP, it may be re-melted with minimum heat and re-stirred until cold.

21. Stock bases can be made successfully by pouring the melted mixture into a warmed jar, covering and allowing to stand, undisturbed on a non conducting surface, until set. (paraffin, simple or wool alcohol ointments of B.P.)
Solids Completely or partially soluble solids should be added in fine powder to the molten base at very low temperature and the mixture stirred until cold.
Liquids such as methyl salicylate and coal tar solutions and semi solids such as ichthammol should be added just as the base is thickening, at about 40C. When a solid is soluble in liquid ingredient, (menthol in methyl salicylate), its more convenient to add it in solution.
Insoluble solids (calamine, starch, zinc oxide) should be passed through a 180 um sieve and added in small amount while stirring to melted base, when it shows first sign of thickening. Sedimentation should be prevented.
If the product has liquid paraffin or a fixed oil, small amount can be used to levigate powder before adding to base to produce a smoother product.

22. MIXING BY TRITURATION:
This is applicable when medicament is a solid insoluble in base or a liquid present in small amount.
Solids should be finely powdered and passed via sieve. (250 um/180 um/125 um mesh).
Trituration can be carried out with an ointment tile and a spatula or using mortar and pestle.
TRITURATION USING TILE AND SPATULA:
Tiles should be large enough to prepare ointments.
Spatula should be flexible and have a broad, non-tapering long blade, to provide a large rubbing surface.
Another small spatula may be used for removing accumulated material.
Powders for incorporation are placed on the tile and mixed gently.
Powders are levigated until mixture is smooth and homogenous.

23. Dispersion is then diluted with increasing amounts of base, doubling the quantity on each addition.
Finally any liquid ingredients are incorporated, avoiding splashes.
TRITURATION USING MORTAR AND PESTLE:
The mortar should have a flat base and the pestle is flat headed to give best results.
Warming equipment can be helpful if the base is very stiff.
Sequence of mixing is same as for the tile method.
Splashing of liquids is easily controlled in the mortar.

24. STORAGE AND Dispensing
Ointments should be stored in tightly closed and completely filled containers
Changes in temperature can lead to the crystallization of the drug and to changes in the ointment base.
They are usually dispensed in jars of glass or plastic material or in collapsible tubes.
Sterile ointments must be dispensed in tubes or single dose units in order to protect the product against contamination during use.
With tin tubes, there is a risk of corrosion with hydrophilic ointments.