Pharmaceutics I — B.Pharmacy 1st Semester
Pharmaceutics I is the introductory subject to the science of drug formulation and delivery. It covers the fundamental concepts of dosage forms, their preparation, and the pharmaceutical processes involved in manufacturing.
Unit 1: Introduction to Pharmaceutics
Pharmaceutics is the science that deals with the design, formulation, manufacture, and evaluation of dosage forms. It bridges the gap between drug discovery and patient use.
History of Pharmacy
Pharmacy has evolved from ancient remedies to modern pharmaceutical sciences. Key milestones include the establishment of the first apothecary shops in the 8th century, the development of pharmacopoeias, and the modern era of pharmaceutical manufacturing.
Dosage Forms Classification
- Solid dosage forms: Tablets, capsules, powders, granules, pills
- Liquid dosage forms: Solutions, suspensions, emulsions, syrups, elixirs
- Semisolid dosage forms: Ointments, creams, gels, pastes, suppositories
- Gaseous dosage forms: Aerosols, inhalers, nebulizers
- Novel drug delivery systems: Liposomes, nanoparticles, transdermal patches
Unit 2: Prescription
A prescription is a written order from a registered medical practitioner to a pharmacist, directing the preparation and dispensing of medicine for a patient.
Parts of a Prescription
- Superscription: Symbol Rx (Latin: Recipe — “take”)
- Inscription: Name and quantity of ingredients
- Subscription: Directions to the pharmacist for preparation
- Signa (Sig.): Directions for the patient
Handling and Dispensing of Prescriptions
The pharmacist must verify the prescription for completeness, check for drug interactions, ensure correct dosage, and properly label the dispensed medication with clear instructions.
Unit 3: Powders
Powders are one of the oldest dosage forms. They are intimate mixtures of dry, finely divided drugs and/or chemicals.
Advantages of Powders
- Flexible dosing — easily adjusted
- More stable than liquid dosage forms
- Faster dissolution than tablets and capsules
- Easy to administer to children and elderly
Methods of Size Reduction (Comminution)
- Trituration: Grinding in a mortar and pestle
- Levigation: Reducing particle size by adding a liquid and grinding
- Pulverization by intervention: Adding a volatile solvent to aid grinding, then evaporating
Mixing of Powders — Geometric Dilution
When mixing a potent drug with a diluent, geometric dilution ensures uniform distribution. Start with the smallest quantity of the most potent ingredient and add an equal volume of diluent, mix thoroughly, then continue doubling until all ingredients are incorporated.
Unit 4: Monophasic Liquid Dosage Forms
Solutions
Solutions are homogeneous mixtures of two or more substances. In pharmacy, solutions typically contain a solid solute dissolved in a liquid solvent.
Types of Solutions
- Syrups: Concentrated aqueous solutions of sucrose (66.7% w/w). Vehicle for unpleasant-tasting drugs.
- Elixirs: Clear, sweetened, hydroalcoholic solutions. Alcohol content provides better solubility for certain drugs.
- Spirits: Alcoholic or hydroalcoholic solutions of volatile substances (e.g., Spirit of Ammonia).
- Linctuses: Viscous oral liquids for cough relief, containing demulcents and soothing agents.
Unit 5: Biphasic Liquid Dosage Forms
Suspensions
A pharmaceutical suspension is a coarse dispersion of insoluble solid particles (internal phase) dispersed in a liquid medium (external phase). Particle size ranges from 1–50 μm.
Emulsions
An emulsion is a biphasic system containing two immiscible liquids, one dispersed as globules in the other, stabilized by an emulsifying agent.
- Oil-in-Water (O/W): Oil globules dispersed in water. Example: milk, vanishing cream
- Water-in-Oil (W/O): Water globules dispersed in oil. Example: butter, cold cream
HLB (Hydrophilic-Lipophilic Balance) System
The HLB system classifies emulsifying agents based on their relative hydrophilic and lipophilic properties. HLB values range from 0–20:
- HLB 3–6: W/O emulsifying agents
- HLB 7–9: Wetting agents
- HLB 8–18: O/W emulsifying agents
- HLB 13–15: Detergents
- HLB 15–18: Solubilizing agents
Important Exam Questions
- Define and classify dosage forms with examples
- Write the parts of a prescription with an example
- Explain the method of geometric dilution
- Differentiate between O/W and W/O emulsions
- Explain the HLB system with its applications
- Write a note on pharmaceutical suspensions