Phases in drug developments I: Pre-clinical studies Kausar Ahmad Department of Pharmaceutical Technology Kulliyyah of Pharmacy akausar@iium.edu.my http://staff.iium.edu.my/akausar RM-KAHS

Phases in drug development Preformulation Chemical evaluations Dosage form design Determination of dosage forms & product formulation Early stage development Pharmaceutical, animal study and in-vitro evaluation Late stage development In-vivo and clinical evaluations RM-KAHS

Preformulation Understanding physicochemical parameters of a drug Characterization of drug molecule Application of biopharmaceutical principles Drug delivery system Dosage form drug has already been discovered. RM-KAHS

Physicochemical properties Spectroscopy Solubility pKa Partition coefficient Melting point Crystal properties and Polymorphism Particle size shape surface area microscopy Powder flow Compression properties Stability studies Excipient compatibility RM-KAHS

Physicochemical properties to produce a simple method for analysing the drug spectroscopy for identifying the best salt to develop and for producing liquid dosage forms solubility which reflects, for example, crystalline solubility melting point necessary for drug stability studies, perhaps employing thin layer- or high pressure liquid- chromatography assay development in solution and in the solid state, alone or with excipients stability to determine crystal morphology and particle size and polymorphism Microscopy necessary data for capsule & tablet formulation powder flow & compression properties to ensure that dosage forms perform correctly excipient compatibility RM-KAHS

Spectroscopy To confirm drug structure and functional groups Usually by UV. to quantify amount of drug in a particular solution use wavelength at λmax the amount of light absorbed is proportional to concentration (C) and the path length of the solution (L) through which the UV light has passed. Beer-Lambert’s Law Non-UV spectroscopy: Vibrational spectroscopy IR Raman spectrum NMR spectrometry 1H-NMR and 13C-NMR Mass spectrometry RM-KAHS

pKa Determination of the dissociation constant for a drug - capable of ionization within a pH range of 1 to 10 This is important since solubility, and consequently absorption, can be altered by changing pH (buffer). The Henderson-Hasselbalch equation provides an estimate of the ionized and un-ionized drug concentration at a particular pH. For weak acids: pH = log10 (Conc Acids/ Conc Salts) For weak bases: pH = log10 (Conc Salts/ Conc Bases) RM-KAHS

Rate of dissolution Determination of the rate is important when it is the rate limiting step in the drug absorption process. If solubility of drug > 10 mg/ml, at pH7, there will be no problem of bioavailability or dissolution (Kaplan,1972) Done by placing product in basket, rotate at 100 rpm, 20 mm from bottom of a 1 L flat bottomed dissolution flask which contain 1L of fluid at 370C. The amount of drug release is then monitored, usually by UV spectrometry, with time (eg. 0, 5, 15, 30, 45 mins) Fluid used : 0.05M HCL (gastric, pH1), phosphate buffer (intestinal, pH7) and distilled water Dissolution rate depends on : Intrinsic solubility, pKa and pH of surrounding (bulk dissolution medium or microenvironment created by the dissolving salts) RM-KAHS

Partition coefficient Partition coefficient (oil/water) indicates ability of a drug to cross cell membranes. It is defined as the ratio of un-ionized drug distributed between the organic and aqueous phases at equilibrium. Biological membranes are lipoidal in nature. Thus, the rate of drug transfer for passively absorbed drugs is directly related to the lipophilicity of the molecule. Po/w = (Coil/Cwater) equilibrium This balance has been shown to be a contributing factor for the rate and extent of drug absorption. Drugs having values of P greater than 1 are classified as lipophilic, whereas those with partition coefficients less than 1 are indicative of a hydrophilic drug. RM-KAHS

Melting Point Affected by purity Affected by types of polymorphs 3 types of measuring MP: – Capillary melting – Hot stage microscopy – Differential Thermal Analysis or Diff Scanning calorimetry Capillary melting observe melting in a capillary tube Only. Hot stage microscopy used microscope with a heated and lagged sample stage; allowing 3 transition phases be observed – 1st melt > 50% melt > complete melting Differential thermal analysis allows all the various phase changes be observed. RM-KAHS

Crystal Properties & Polymorphism Need to determine crystal morphology and particle size A polymorph is a solid material with two or more different molecular arrangements and having a distinct crystal shape. These differences disappear in the liquid or vapour state. Polymorphs generally have different melting points, x-ray diffraction patterns, and solubilities, even though they are chemically identical. Dissolution rate affects bioavailability Tensile strength affects compression ability Different stability at various temperature & pressure In general, the stable polymorph exhibits the highest melting point, the lowest solubility, and the maximum chemical stability Critical issues in formulation: No. of polymorphs exisiting for the substance Identify pseudopolymorphism or true polymorphism Stability of the different polymorphs Is there an amorphous glass? Can the metastable be stabilised? What is the solubility and melting points of each forms? Will the more soluble form be stable after processing and storage? RM-KAHS

Particle properties Properties of drugs are affected by particle size and shape. Particle size is critical in dose uniformity and dissolution rate of solid dosage forms. poorly soluble drugs have low dissolution rate & hence low bioavailability. But bioavailable when administered in a finely subdivided state rather than as a coarse material. Suspensions and creams are more uniform if the ingredients used are in micronised form. Bulk flow, formulation homogeneity, dissolution and chemical reactivity are directly affected by size, shape & surface morphology of the drug particles as well as particle size distribution. Size can also be a factor in stability of tablets; fine materials are relatively more prone to attack from atmospheric oxygen, humidity, and interacting excipients compared to coarse materials. RM-KAHS

Powder Flow & Compression Properties necessary data for capsule & tablet formulation Ease of operation Homogeneity Uniform unit dose Factors Particles sizes distribution Chemical characteristics of substances Differences in polymorphs Drug-excipient interactions Drug-environmental & excipient-environmental interactions Assessing powder flow by: Measuring bulk density/tapped density Measuring angle of repose Use of Carr’s index (%) for Bulk density = (Tapped density – Poured density) / Tapped density Carr’s index of 5 – 16 show good flow Use of Hausner ratio = Tapped density / Poured density Hauser ratio of less than 1.25 show good flow Assesing the angle of repose, the angle of a conical mound of powder to the horizontal (θ ) θ with less than 30 show good flowability Powder Compression Properties Crucial for tablet dosage forms. Most drug has poor compression properties, thus requiring compression aids. If dose < 50mg, tablets can be prepared by direct compression using modern direct compression excipients. If dose is high and drug does not have good compressibility, use wet granulation method. To form good tablet, materials should be plastic (capable of permanent deformation) while also exhibit a degree of brittleness (fragmenting) If drug dose is high and behave plastically, then add excipient that fragments (lactose, calcium phosphate) If drug is brittle or elastic, add excipients that are plastic RM-KAHS

Polyamide: Carrier for insoluble ingredients; Protector for sensitive ingredients; Slow delivery & long lasting effect 7 m, empty spheres 10 m, porous PHM4153 Dosage Design 2 2011/12

Excipient: Particle size distribution PHM4153 Dosage Design 2 2011/12

Excipient: Pore volume & pore diameter PHM4153 Dosage Design 2 2011/12

Chemical Stability of Active Compounds Study of intrinsic stability of the active components allow better approaches to formulation, selection of excipients, use of protective additives and accurate selection of suitable materials and design of packaging. Include both solution and solid state experiments under conditions typical for the handling, formulation, storage, and administration of a drug candidate as well as stability in presence of other excipients. Usually the first quantitative assessment Max shelf-life allowable is 5 years Factors influencing chemical stability in dosage form: Temperature & humidity pH, ionic strength Co-solvent, dosage form diluent. Light Oxygen Stress conditions used: Elevated temperature studies Stability under High-Humidity Conditions Photolytic Stability Oxidative Stability RM-KAHS

Excipients & Product Stability Excipients are important for processing and efficacy For tablets: binders, disintegrants, lubricants, and fillers. For liquids: preservatives, thickener, colorants, flavours, sweeteners, buffer and water Techniques to screen drug-excipient compatibility: Thin-layer chromatography Differential thermal analysis Diffuse reflectance spectroscopy RM-KAHS

Incompatibility Chemical pH/dissociation pH/disperse systems polyvalent cations complexation cationic and anionic compounds of high MW reducing agents (cause fading of dyes) Physical Immiscibility Insolubility Packaging Formulation and packaging materials PHM4153 Dosage Design 2 2011/12

Detection of Incompatibility Cracked cream Hydrolysis or oxidation Discoloration Precipitation PHM4153 Dosage Design 2 2011/12

Other factors to be considered in preformulation Consumer’s preferences Compatibility of packaging materials Facility and equipment capabilities Market needs Child-resistance packaging Security/Protection RM-KAHS

Route of administration Dosage form design Ailment Route of administration Enteral Oral tablets Rectal suppositories Parenteral Intravascular vaccines Subcutaneous Creams Bio Pharmaceutics Packaging RM-KAHS

Dosage form Tablets, liquids, capsules, creams, ointments, vaccines Optimise formulation (& processes) Use required excipients Surfactants Anti-oxidants Preservatives Binders RM-KAHS

Formulation Process whereby drugs are combined with other substances (excipients) e.g. preservative to produce dosage forms e.g. cream suitable for administration to or by patients. Every medicinal product is a combination of the drug substance and excipients. Knowledge of the composition, function, and behavior of excipients is a prerequisite to the successful design, development and manufacture of pharmaceutical dosage forms. PHM4153 Dosage Design 2 2011/12

Formulation requirement: efficacy, safety, and quality Contain accurate dose Convenient to take or administer Provide drug in a form for absorption or other delivery to the target Retain quality throughout shelf life & usage period Manufactured by a process that does not compromise performance and that is reproducible and economical PHM4153 Dosage Design 2 2011/12

Categories of excipients Provide essential parts of dosage form & enhance bioavailability Emulsifiers Viscosity modifier Prevent degradation of the formulation: protect, improve safety & enhance stability Anti-oxidants Anti-bacterials Preservatives UV absorbers Aid processing during manufacturing Assist product identification  colour Excipients in creams: Base SAA Anionic - SDS Non-ionic – Span, Tween Anti-oxidants – BHA, BHT Preservatives: methyl and propyl paraben (potency, integrity, prevent microbial growth) Stearic acid Stearyl alcohol, cetyl alcohol Glycerol monostearate Lanolin Glycerin Zinc stearate opacifying agent, dusting powder….. Fragrance, dyes PHM4153 Dosage Design 2 2011/12

Choosing excipients physiological inertness physical and chemical stability conformance to regulatory agency requirements no interference with drug bioavailability absence of pathogenic microbial organisms commercially available at low cost No single excipient would satisfy all the criteria; therefore, a compromise of the different requirements has to be made. For example, although widely used in pharmaceutical tablet and capsule formulations as a diluent, lactose may not be suitable for patients who lack the intestinal enzyme lactase to break down the sugar, thus leading to the gastrointestinal tract symptoms such as cramps and diarrhea. What about excipients in creams? PHM4153 Dosage Design 2 2011/12

Pharmaceutical evaluation Product testing Tablets Hardness Disintegration Creams Viscosity Microbial Diffusion Animal study Efficacy of product RM-KAHS

Example RM-KAHS

Summary RM-KAHS

References Aulton, M.E. (2002). Pharmaceutics – The Science of Dosage Form Design (2nd Ed.). Churchill Livingstone. Bugay, D. E. (1999). Pharmaceutical excipients : characterization by IR, Raman, and NMR spectroscopy. Kibbe, A. H. (2000). Handbook of pharmaceutical excipients. Rowe, R. C., Sheskey, P. J. & Owen, S. C. (2006). Handbook of pharmaceutical excipients Rowe, R. C. (2009). Handbook of pharmaceutical excipients. RM-KAHS