Question 1

What is the maximum daily dose of paracetamol for adults and when should it be reduced?

Accepted Answer

The standard maximum paracetamol dose for adults is 4 g/day (1 g every 4–6 hours, max 4 doses in 24 hours). This should be reduced to 2 g/day (500 mg every 6 hours) in: chronic alcohol use or liver disease, malnutrition or low body weight (<50 kg), hepatic impairment (any cause), and elderly patients with frailty. Paracetamol overdose (intentional or accidental) is the most common cause of acute liver failure in the UK — the threshold for N-acetylcysteine treatment is 75 mg/kg in standard-risk patients. Paracetamol is the safest first-line analgesic in pregnancy (all trimesters), renal impairment (no dose reduction required), and the elderly.

Question 2

Which antibiotics are absolutely contraindicated in pregnancy?

Accepted Answer

Absolutely contraindicated throughout all trimesters: Tetracyclines (doxycycline, minocycline) — cause permanent dental staining and bone growth inhibition in the fetus; Fluoroquinolones (ciprofloxacin, levofloxacin) — risk of cartilage damage; Chloramphenicol in the third trimester — "grey baby syndrome" (cardiovascular collapse). Contraindicated primarily in first trimester: Clarithromycin (teratogenic in animal studies); Trimethoprim (folate antagonist — risk of neural tube defects; safe in T2/T3 with folic acid supplementation); Co-trimoxazole (folate antagonist in T1, neonatal jaundice in T3). Safe antibiotics throughout all trimesters: Amoxicillin, Ampicillin, Cefalexin, Cefuroxime, Erythromycin (not estolate), Clindamycin, Nitrofurantoin (avoid at term), Metronidazole (caution in T1).

Question 3

Which drugs require dose reduction in renal impairment (eGFR less than 30)?

Accepted Answer

Key drugs requiring dose reduction or avoidance at eGFR <30 mL/min/1.73m²: STOP — Metformin (lactic acidosis risk), NSAIDs (further renal deterioration), Nitrofurantoin (ineffective and toxic), SGLT2 inhibitors. REDUCE dose — Digoxin (increase toxicity risk; reduce dose by 50%), Gabapentin and Pregabalin (significant accumulation), Trimethoprim (hyperkalaemia, creatinine rise), Low-molecular-weight heparins (anti-Xa monitoring or switch to unfractionated heparin). CAUTION — ACE inhibitors and ARBs (monitor eGFR and K+ closely; acceptable to continue if stable). Opioids (morphine, codeine) require dose reduction due to active metabolite accumulation — use Fentanyl or Buprenorphine (less renal-dependent) for chronic pain. Always check BNF Appendix 3 (renal impairment) before prescribing in CKD.

Question 4

What are the most important drug interactions with warfarin?

Accepted Answer

Drugs that INCREASE INR (bleeding risk) — highest clinical significance: Metronidazole (potent CYP2C9 inhibitor — can double INR), Fluconazole and azole antifungals, Clarithromycin and erythromycin, Ciprofloxacin and fluoroquinolones, Amiodarone (persists weeks after stopping), NSAIDs (additive antiplatelet effect + GI bleeding risk), Omeprazole and other PPIs (modest effect), Aspirin (even low-dose). Drugs that DECREASE INR (clot risk) — CYP2C9 inducers: Rifampicin (dramatic reduction — avoid combination), Carbamazepine, Phenytoin, Phenobarbital, St John's Wort. Rule: check INR 3–5 days after starting any new medication in a warfarin-treated patient.

Question 5

What is the antibiotic of choice for community-acquired pneumonia in a GP outpatient?

Accepted Answer

For low-severity CAP in outpatients (CURB-65 score 0–1): Amoxicillin 500 mg TDS × 5 days is first-line (covers Streptococcus pneumoniae, the most common pathogen). If atypical organisms suspected (Mycoplasma pneumoniae — young adults, gradual onset, dry cough, bilateral changes): add Clarithromycin 500 mg BD × 5 days or use Doxycycline 200 mg stat then 100 mg OD × 5 days as monotherapy. Penicillin allergy: Doxycycline 200 mg stat then 100 mg OD × 5 days or Levofloxacin 500 mg OD × 5 days (reserve for patients failing first-line). For CURB-65 ≥2: hospital admission usually required. Never use fluoroquinolones as first-line for mild community-acquired pneumonia.

Question 6

What is the correct dose of morphine for severe pain in adults and what monitoring is required?

Accepted Answer

For acute severe pain in opioid-naive adults: oral immediate-release Morphine 5–10 mg every 4 hours (modified to 2.5–5 mg in elderly or frailty). IV/SC Morphine: 2.5–5 mg every 4 hours (titrate by 30–50% increments). Breakthrough dose: 1/6 of total daily opioid dose. Monitoring required: respiratory rate (withhold if RR <12/min), sedation score, pain score, bowel function (prescribe laxatives prophylactically — senna + lactulose). Antidote: Naloxone 400 mcg IV/IM (repeat every 2–3 min up to 10 mg for severe respiratory depression). Dose reduction in renal impairment (use Fentanyl or Oxycodone if eGFR <30), hepatic failure, and COPD with CO2 retention. Codeine is ineffective in poor CYP2D6 metabolisers (5–10% of population).