1. Dosage Forms Overview 💊

Dosage forms are the physical form of a drug product designed for administration to patients. The choice of dosage form affects drug stability, bioavailability, and patient compliance.

Category	Dosage Forms	Characteristics	Examples
SOLID	Tablets	Compressed powders, most common form	Paracetamol 500mg tablet
	Capsules	Hard or soft gelatin shells	Amoxicillin 500mg capsule
	Powders	Fine particles for reconstitution	Oral Rehydration Salts
	Suppositories	Melt at body temperature	Glycerin suppository
LIQUID	Solutions	Homogeneous, clear mixtures	Paracetamol syrup
	Suspensions	Particles dispersed in liquid (shake well!)	Amoxicillin suspension
	Emulsions	Two immiscible liquids (O/W or W/O)	Cod liver oil emulsion
SEMISOLID	Ointments	Greasy, occlusive (hydrocarbon base)	Petroleum jelly
	Creams	O/W or W/O emulsions, vanishing	Hydrocortisone cream
	Gels	Semisolid, transparent, non-greasy	Clindamycin gel

💡 Board Exam Tip:

Know the difference between O/W and W/O emulsions! O/W (oil-in-water) is water-washable and less greasy. W/O (water-in-oil) is greasier and provides better occlusion. Test with dilution: O/W dilutes with water, W/O dilutes with oil.

2. Tablet Manufacturing 🏭

Understanding tablet manufacturing processes is essential for quality control and troubleshooting formulation problems.

Direct Compression:

Simplest method, fewer steps
Drug + excipients → compress directly
Best for drugs with good flow properties
Less heat/moisture exposure

Wet Granulation:

Most common method
Powder + binder solution → granules → dry → compress
Better flow and compressibility
Not for moisture-sensitive drugs

Excipient Type	Function	Examples
Diluent/Filler	Bulk up tablet to practical size	Lactose, MCC, Starch
Binder	Hold ingredients together	PVP, Starch paste, HPMC
Disintegrant	Help tablet break apart	Croscarmellose, Crospovidone
Lubricant	Prevent sticking to dies	Magnesium stearate, Stearic acid
Glidant	Improve powder flow	Colloidal silica (Aerosil), Talc
Colorant	Identification, aesthetics	FD&C dyes, Iron oxides

3. Drug Delivery Systems 🚚

Modern drug delivery systems aim to improve efficacy, reduce side effects, and enhance patient compliance through controlled and targeted drug release.

System Type	Mechanism	Advantages	Examples
Extended Release (ER)	Slow, continuous release over time	Less frequent dosing, steady levels	Metformin XR, Metoprolol ER
Delayed Release (DR)	Release after delay (e.g., enteric coating)	Protect stomach, target intestine	Omeprazole DR, Aspirin EC
Transdermal	Drug absorption through skin	Bypass first-pass, sustained release	Nicotine patch, Fentanyl patch
Osmotic Systems	Water enters, pushes drug out	Zero-order release, food-independent	OROS (Concerta), Glucotrol XL
Liposomes	Phospholipid vesicles carrying drug	Targeted delivery, reduced toxicity	Doxil (liposomal doxorubicin)

⚠️ Important Warning:

Extended-release tablets should NOT be crushed, chewed, or split (unless scored). Doing so destroys the release mechanism and can cause dose-dumping, leading to toxicity!

4. Sterile Products and Parenterals 💉

Parenteral products are administered by injection and must be sterile, pyrogen-free, and isotonic for safe administration.

Routes of Injection:

IV (Intravenous): Fastest onset, 100% bioavailability
IM (Intramuscular): Deltoid, gluteus, vastus lateralis
SC (Subcutaneous): Slower absorption, insulin
ID (Intradermal): Tuberculin test, allergy testing

Quality Requirements:

Sterility: No microorganisms
Pyrogen-free: No fever-causing substances
Isotonicity: 0.9% NaCl equivalent (285-310 mOsm/L)
Particulate-free: No visible particles
Correct pH: Minimize tissue irritation

Sterilization Method	Conditions	Applications
Autoclaving (Steam)	121°C, 15 min, 15 psi	Heat-stable solutions, equipment
Dry Heat	160-180°C, 1-2 hours	Glassware, powders, oils
Filtration	0.22 μm membrane filter	Heat-sensitive solutions
Gamma Radiation	2.5 Mrad	Disposables, some drugs

5. Compounding Calculations 📐

Accurate calculations are critical in compounding to ensure patient safety and therapeutic effectiveness.

Essential Compounding Calculations:

Percentage Concentration:

%w/w: g solute / 100g preparation (solids)
%w/v: g solute / 100mL preparation (solutions)
%v/v: mL solute / 100mL preparation (liquids)

Dilution Formula:

C₁V₁ = C₂V₂

Where C = concentration, V = volume

Alligation Method:

Used to determine proportions when mixing different strengths

Parts of higher = Desired - Lower strength

Parts of lower = Higher strength - Desired

Isotonicity (Sodium Chloride Equivalent):

NaCl needed (g) = 0.9 - (E × drug concentration)

Where E = NaCl equivalent of drug

💡 Quick Reference:

1% = 10 mg/mL = 1 g/100mL
1:1000 = 0.1% = 1 mg/mL
1:10,000 = 0.01% = 0.1 mg/mL
Normal saline = 0.9% NaCl = isotonic

6. Practice Questions 📝

Question 1: Dosage Forms

What is the main difference between an ointment and a cream?

Answer: Ointments have a hydrocarbon (greasy) base and are occlusive, while creams are emulsions (O/W or W/O) that are less greasy and water-washable. Ointments provide better barrier protection and are preferred for dry, scaling conditions. Creams are cosmetically more acceptable and preferred for wet, weeping lesions.

Question 2: Excipients

Why is magnesium stearate added in small amounts (0.5-2%) to tablet formulations?

Answer: Magnesium stearate is a lubricant that prevents sticking of tablet powder to dies and punches. However, excess amounts can form a hydrophobic film around drug particles, reducing dissolution rate and bioavailability. It's used in minimal effective amounts.

Question 3: Drug Delivery

Why are enteric-coated tablets designed to resist gastric acid?

Answer: Enteric coatings protect drugs that are degraded by stomach acid (e.g., omeprazole), protect the stomach from irritating drugs (e.g., aspirin), or target drug release to the intestine for local effect. The coating dissolves at intestinal pH (>5.5) but remains intact in acidic stomach (pH 1-3).

Question 4: Compounding Calculation

How many grams of hydrocortisone powder are needed to prepare 60g of 2.5% hydrocortisone cream?

Answer: 1.5 grams. Calculation: 2.5% w/w = 2.5g per 100g. For 60g: (2.5g/100g) × 60g = 1.5g of hydrocortisone powder.

Pharmaceutics