DHA Pharmacist 4

Question 1

A patient is prescribed warfarin and starts taking clarithromycin for a respiratory infection. What is the most likely pharmacokinetic interaction?

Accepted Answer

Clarithromycin inhibits CYP3A4 and CYP2C9, increasing warfarin levels

Answer

Clarithromycin is a potent CYP3A4 and CYP2C9 inhibitor, which reduces warfarin metabolism and increases its anticoagulant effect, raising bleeding risk.

Question 2

Under DHA regulations, which category of medications requires a triplicate prescription in the UAE?

Accepted Answer

Controlled substances (narcotics and psychotropics)

Answer

UAE law requires controlled substances such as narcotics and psychotropics to be dispensed only on triplicate prescriptions issued by licensed practitioners.

Question 3

A pediatric patient weighing 20 kg requires amoxicillin at 40 mg/kg/day divided every 8 hours. What is the correct dose per administration?

Accepted Answer

267 mg

Answer

Total daily dose = 40 mg/kg × 20 kg = 800 mg/day; divided every 8 hours gives 800 ÷ 3 ≈ 267 mg per dose.

Question 4

Which parameter best describes the fraction of an oral drug that reaches systemic circulation unchanged?

Accepted Answer

Bioavailability

Answer

Bioavailability (F) is defined as the fraction of an administered dose that reaches the systemic circulation in its active form.

Question 5

A patient on methotrexate for rheumatoid arthritis is also prescribed ibuprofen. What is the primary concern?

Accepted Answer

NSAIDs reduce renal clearance of methotrexate, causing toxicity

Answer

NSAIDs inhibit renal prostaglandin synthesis, reducing renal blood flow and tubular secretion of methotrexate, leading to methotrexate accumulation and toxicity.

DHA - Dubai Health Authority Practice Test

DHA - Dubai Health Authority Practice Test

DHA Pharmacist 4