Wattle Pharmacy Prep

Dosage form design
Practice questions with explanations

Dosage form design belongs to Medicinal chemistry and biopharmaceutics, which makes up about 10% of the Overseas Pharmacist Readiness Assessment (OPRA®). Answer each question yourself before opening the explanation.

1. Which property of a suspension affects the accuracy of a measured dose?

  1. The colour of the suspension
  2. The type of closure
  3. The size of the bottle
  4. The rate of sedimentation and the ease of redispersion, which determine whether shaking produces a uniform mixture
Show answer

D. The rate of sedimentation and the ease of redispersion, which determine whether shaking produces a uniform mixture

A suspension that cakes into a hard sediment cannot be redispersed by shaking, so doses become progressively inaccurate. Formulators use controlled flocculation and suspending agents so that the sediment stays loose. This is why a suspension that has separated into a solid layer that will not remix should be discarded rather than used.

2. What is the function of a disintegrant such as croscarmellose sodium in a tablet?

  1. It binds the powder particles together during compression
  2. It swells on contact with water, breaking the tablet into granules to expose surface area for dissolution
  3. It prevents the tablet sticking to the punches
  4. It masks the taste of the active ingredient
Show answer

B. It swells on contact with water, breaking the tablet into granules to expose surface area for dissolution

A disintegrant is added so that the compressed mass breaks apart quickly in gastrointestinal fluid, since a tablet that does not disintegrate cannot dissolve and cannot be absorbed. Superdisintegrants such as croscarmellose and sodium starch glycolate work by rapid swelling and wicking. Binders hold granules together, lubricants such as magnesium stearate prevent sticking, and taste masking is achieved by coating or by choosing a different salt.

3. Why is a preservative required in a multi-dose aqueous preparation?

  1. To prevent the drug from crystallising
  2. To prevent microbial growth introduced during repeated opening and use
  3. To keep the pH constant
  4. To prevent chemical degradation of the active ingredient
Show answer

B. To prevent microbial growth introduced during repeated opening and use

Water supports microbial growth, and every withdrawal risks contamination, so multi-dose aqueous products contain agents such as benzalkonium chloride, parabens or phenoxyethanol. Preservative efficacy is a formal test requirement. Single-dose and preservative-free presentations exist for eyes with damaged epithelium and for patients who react to benzalkonium, and once opened they must be discarded promptly.

These are 3 of the 40 questions on dosage form design in the app.

All 2,200 questions, offline

Wattle Pharmacy Prep has every question with a full explanation, practice by area and topic, timed 120-question mock exams in 150 minutes, and a readiness score that only counts a question once you have answered it correctly twice in a row. One purchase, no subscription, no account, fully offline.

Download on the App StoreGet it on Google Play

More topics in Medicinal chemistry and biopharmaceutics

Drug stability and degradation · Functional groups and drug classes · Pharmaceutical excipients · Solubility and partitioning · Sterile products · Structure-activity relationships