Pharmaceutical dosage forms and delivery systems

Learning objectives: Learn about the different Pharmaceutical dosage forms and delivery systems, their rationale and uses.

Pharmaceutical dosage forms and delivery systems

Practice questions

Dosage forms and delivery systems

■  Which inhaler type delivers powdered drug by patient inhalation?

• Correct Answer: Dry powder inhaler or DPI 

• Explanation: A dry powder inhaler (DPI) is breath-activated. It releases the powdered medication only when the patient takes a strong, deep inhalation (examples include Turbuhaler and Diskus devices).

■  Depot injections are designed for:

• Correct Answer: Sustained release

• Explanation: Depot injections are formulated with oil vehicles or biodegradable polymers that slow down drug absorption, releasing the medication gradually over weeks or months (such as haloperidol decanoate IM).

■  Which metabolism process does sublingual route avoids:

• Correct Answer: A. Hepatic first-pass metabolism

• Explanation: Drugs placed under the tongue dissolve and enter the systemic circulation directly via venous drainage, bypassing processing by the liver.

■  Liposomes are used to improve:

• Correct Answer: Solubility & bioavailability

• Explanation: Liposomes encapsulate hydrophobic (water-fearing) drugs inside lipid bilayers. This increases their solubility, decreases systemic toxicity, and allows for targeted drug delivery (such as liposomal amphotericin B).

■  Which parenteral formulation must be isotonic with plasma?

• Correct Answer: All of the Intravenous (IV), Intramuscular (IM), and Subcutaneous (SC) formulations

• Explanation: Intravenous (IV), Intramuscular (IM), and Subcutaneous (SC) formulations must maintain the same osmotic pressure as blood plasma to prevent cell damage (shrinking or bursting) and minimize injection pain.

Excipients and formulations

■  Which dosage form provides controlled release via osmotic pressure?

• Answer: OROS tablet

• Explanation: OROS (Osmotic-controlled Release Oral System) uses an osmotic gradient to push the drug out slowly.

■  Which excipient acts as a diluent in tablets?

• Answer: Lactose

• Explanation: Lactose and starch are fillers/diluents used to increase the bulk volume of a tablet.

■  Which coating is used for enteric protection?

• Answer: Shellac

• Explanation: Enteric coatings (such as shellac or cellulose acetate phthalate) prevent dissolution in gastric fluid. Shellac is a natural resin secreted by the female lac bug (Kerria lacca) on trees.

■  PEG (polyethylene glycol) is most commonly used as:

• Answer: Solvent / vehicle

• Explanation: PEG is hydrophilic and commonly serves as a solvent, plasticizer, or ointment base.

■  Which suspension stabilizer prevents caking?

• Answer: Sodium carboxymethylcellulose

• Explanation: Carboxymethylcellulose (CMC) functions as a suspending agent that prevents rapid sedimentation and subsequent caking.

■  Particle size reduction increases:

• Answer: Dissolution rate

• Explanation: Decreasing particle size increases total surface area, which raises the dissolution rate according to the Noyes-Whitney equation.

■  Which law governs drug diffusion?

• Answer: Fick's law

• Explanation: Fick's law states that diffusion rate is directly proportional to the concentration gradient and surface area, and inversely proportional to membrane thickness. 

■  Microencapsulation is used for:

• Answer: Controlled release

• Explanation: Coating tiny drug particles with thin polymeric membranes allows for slow, sustained drug release.

■  Which dosage form has maximum Bioavailability or 100% bioavailability?

• Answer: IV injection

• Explanation: Intravenous delivery completely bypasses absorption barriers, delivering the entire dose directly into systemic circulation.

■  Which formulation avoids hepatic first-pass metabolism or bypasses First-Pass Metabolism?

• Answer: IV infusion Buccal tablet

• Explanation: Intravenous routes bypass the liver entirely, while the buccal route drains directly into systemic veins, avoiding the hepatic first-pass effect.

However, a buccal tablet is not fully (100%) bioavailable. While the buccal route (placed between the cheek and gums) avoids the hepatic first-pass effect and the harsh acids of the gastrointestinal tract, it does not achieve the complete (100%) systemic absorption seen with intravenous (IV) injection.

Sterilisation & Preservation

■  Which method is the best sterilisation for glassware?

• Answer: Dry heat

• Explanation: Dry heat at 160–170 °C for 2 hours is ideal for glassware, oils, and metals. This method effectively prevents moisture-related damage.

■  What is the use of Benzalkonium chloride? 

• Answer: Preservative 

• Explanation:• It is a cationic surfactant with strong antimicrobial activity. It is widely used in formulations like eye and nasal drops.

■  Which gas is used in gas sterilisation for surgical instruments: 

• Answer: Ethylene oxide 

• Explanation:• This gas is used for heat- and moisture-sensitive items like medical plastics and catheters. Ethylene oxide (EtO) is a flammable, colorless organic gas with a faintly sweet, ether-like odor. It has the chemical formula C₂H₄O and is the simplest epoxide and cyclic ether, featuring a three-membered ring made of two carbon atoms and one oxygen atom. It is widely used to sterilize heat-sensitive medical devices, surgical tools, and single-use equipment because it penetrates packaging and destroys bacteria, viruses, and fungi. Historically and industrially used in fumigation that is applied in small amounts to sterilize spices, cosmetics, or control pests in stored agricultural goods (though increasingly phased out on foods due to residue concerns).

■  Which preservative is contraindicated in neonates?

• Answer: Benzyl alcohol.

• Explanation: Neonates cannot safely metabolise benzyl alcohol which gradually accumulated and leads to metabolic acidosis known as "gasping syndrome".

■  Which one is the official guideline for sterility testing? Which of the following guideline ensures sterility testing?

• Answer: USP 71

• Explanation:• USP 71 specifically governs sterility testing for injectables.

• USP 61 covers microbial limits.

• USP 85 covers bacterial endotoxin tests.

• USP 795 covers non-sterile compounding.

Further reading

• Antibiotic Classes in 7 minutes

• A Brief Overview of Classes of Antibiotics

•