PHARMACEUTICS AND DRUG DELIVERY SYSTEMS — Theory
Definition
Pharmaceutics is the branch of pharmacy that deals with the formulation, preparation, stability, and effectiveness of pharmaceutical dosage forms.
Simple line:
Drug ko powder se tablet, capsule, injection, cream, patch, inhaler banane ka science = Pharmaceutics.
1) Physical & Chemical Behavior of Drug Products
Jab drug milti hai, wo ek chemical hoti hai. Uski nature samajhna padta hai:
Physical properties
| Property | Meaning | Why important |
|---|---|---|
| Melting point | Jis temp pe melt ho | Purity & polymorphism check |
| Solubility | Water me dissolve? | Absorption decides |
| Particle size | Size of drug powder | Dissolution + Bioavailability |
| Polymorphism | Same drug, diff crystal forms | Solubility & stability change |
| Hygroscopicity | Moisture absorb karta | Shelf life & packaging |
| Viscosity | Thickness of liquid | Flow, dosing |
Remember: Physical nature controls drug performance.
Chemical properties
| Property | Meaning | Why matter |
|---|---|---|
| Hydrolysis | Water se breakdown | Esters + Amides degrade |
| Oxidation | Oxygen se spoil | Vitamins, fats degrade |
| Photolysis | Light sensitive | Store in amber bottle |
| Racemization | Enantiomers convert | Potency change |
Goal: Drug ko collapse hone se bachana.
2) Compounding Techniques (Preparation Methods)
Pharmacy compounding = custom medicines banana.
Types:
- Solid compounding → powders, capsules, tablets
- Liquid compounding → syrups, solutions, suspensions
- Semisolid → creams, ointments, gels
- Sterile → injections, eye drops
Methods
| Method | Use |
|---|---|
| Trituration | Fine grinding of powders |
| Levigation | Mix powder into ointment |
| Geometric dilution | Equal mixing technique for potent drugs |
| Fusion method | Melt ingredients (ointments) |
| Filtration 0.22 micron | Sterilization for injections |
Golden rule: Uniformity + Cleanliness + Accuracy
3) Pre-Formulation Studies
Definition:
Before making a dosage form, drug ki scientific investigation karna = pre-formulation.
Goals:
- Drug + excipient compatibility
- Stability study
- Best dosage form decide
- Improve solubility & dissolution
Tests:
| Study | Purpose |
|---|---|
| Melting point | Purity & polymorphism |
| Solubility study | Soluble or not |
| Dissolution study | Rate of drug release |
| Partition coefficient (logP) | Lipophilicity → absorption |
| pKa | Ionization state → absorption |
| Hygroscopicity | Moisture protection |
| DSC/FTIR | Drug–excipient compatibility |
Formula you must know:
Henderson–Hasselbalch for pH-solubility relationship.
4) Biopharmaceutics & Dosage Form Design
Biopharmaceutics studies interaction between drug, dosage form & human body.
Simple code:
Drug form decides drug performance.
Forms
| Dosage form | Why used |
|---|---|
| Solutions | Fast absorption |
| Suspensions | For insoluble drugs |
| Emulsions | For oil + water drugs |
| Tablets | Convenient, stable |
| Capsules | Mask taste, protect drug |
| Injections | Fastest action |
| Patches | Sustained drug release |
| Inhalers | Asthma/direct lungs |
5) Formulation & GMP
Formulation principles
- Choose excipients (fillers, binders, disintegrants, lubricants)
- Mix & compress correctly
- Maintain stability
Stability Testing
| Type | Purpose |
|---|---|
| Accelerated | Predict shelf life |
| Long-term | Final stability claim |
ICH guideline
Ex: 40°C / 75% RH accelerated test.
GMP (Good Manufacturing Practices)
- Clean facility
- Trained staff
- Document everything
- Quality testing
PCI vibe:
“Quality medicine ensures patient safety.”
6) Drug Delivery Routes
| Route | Example | Benefit |
|---|---|---|
| Oral | Tablet | Convenient |
| IV | Injection | Fastest |
| IM/SC | Vaccines | Sustained |
| Topical | Creams | Local action |
| Nasal | Nasal sprays | Quick systemic |
| Inhalation | Inhalers | Direct lungs |
| Transdermal | Patch | Slow release |
7) Bioequivalence
Definition:
Two drugs same blood level = same effect.
Compare:
- Cmax
- Tmax
- AUC
Acceptance:
80–125% rule.
Meaning: Generic = as good as branded.
Quick 5-line Summary
- Pharmaceutics = drug → dosage form science.
- Understand physical + chemical properties for stability.
- Pre-formulation tests ensure right form + excipients.
- GMP ensures quality, safety, effectiveness.
- Bioequivalence proves generic = branded performance.