Pharmacology Flashcards

A patient with heart failure is prescribed digoxin. Which electrolyte abnormality increases the risk of digoxin toxicity?

Answer: Hypokalaemia

Hypokalaemia increases the risk of digoxin toxicity because digoxin and potassium compete for binding at the Na+/K+ ATPase pump. Low potassium levels increase digoxin binding, enhancing its toxic effects including cardiac arrhythmias.

Which antibiotic class is associated with tendon rupture, particularly the Achilles tendon, especially in elderly patients?

Answer: Fluoroquinolones

Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) are associated with tendinopathy and tendon rupture, particularly the Achilles tendon. Risk is increased in patients over 60, those on corticosteroids, and organ transplant recipients.

A patient on warfarin therapy has an INR of 8.5 with no active bleeding. What is the most appropriate management?

Answer: Hold warfarin and administer oral vitamin K

For supratherapeutic INR (>4.5-10) without active bleeding, the recommendation is to hold warfarin and administer low-dose oral vitamin K (1-2.5 mg). FFP and PCC are reserved for active bleeding or INR >10 with high bleeding risk.

Which drug is the antidote for opioid overdose?

Answer: Naloxone

Naloxone is a competitive opioid receptor antagonist used to reverse opioid overdose. It rapidly reverses respiratory depression, sedation, and miosis. Due to its shorter half-life compared to many opioids, repeated doses or an infusion may be needed.

A pregnant woman requires treatment for a urinary tract infection. Which antibiotic is considered safest in the first trimester?

Answer: Amoxicillin

Amoxicillin (category B) is one of the safest antibiotics during pregnancy, including the first trimester. Fluoroquinolones are contraindicated (cartilage damage), tetracyclines (teeth discolouration, bone effects), and trimethoprim is avoided in the first trimester (folate antagonist, neural tube defect risk).

A patient on metformin is scheduled for a CT scan with IV contrast. What precaution should be taken?

Answer: Hold metformin for 48 hours after the contrast study

Metformin should be held at the time of or before contrast administration and withheld for 48 hours after the procedure. IV contrast can rarely cause contrast-induced nephropathy, and impaired renal function combined with metformin increases the risk of lactic acidosis.