A patient on warfarin has an INR of 9 and is bleeding from his gums and in his urine. What should be given to reverse the warfarin?
Answer: IV vitamin K with prothrombin complex
Warfarin blocks vitamin K epoxide reductase, reducing factors II, VII, IX and X. For significant bleeding, give IV vitamin K (5–10 mg) and prothrombin complex concentrate (or fresh frozen plasma if PCC is unavailable) for rapid replacement. Stop the warfarin.
Remember Mesna for the bladder, dexrazoxane for the heart.
Why the other options are wrong
Doxorubicin Cardiotoxicity.
Bleomycin Pulmonary fibrosis.
Vincristine Neuropathy.
Cisplatin Kidney and ear damage.
Question 3Easy
Which laxative acts as a surfactant, letting water and fat penetrate the stool so that it softens?
Answer: Docusate sodium
Docusate is a stool softener (a detergent or surfactant) and also has a mild stimulant effect. Bulk-forming agents (ispaghula) hold water and add bulk; osmotic agents (lactulose, macrogol) draw water into the bowel; stimulants (senna, bisacodyl) increase motility. For opioid constipation a stimulant plus softener is usual; bulk agents are avoided.
A theatre nurse from Lahore has chronic hepatitis C with detectable HCV RNA. She is started on sofosbuvir with daclatasvir for 12 weeks. Which of the following viral targets does sofosbuvir inhibit?
Answer: NS5B RNA-dependent RNA polymerase
Sofosbuvir is a nucleotide analogue prodrug that is converted in hepatocytes to a uridine triphosphate analogue. It is incorporated by the HCV NS5B RNA-dependent RNA polymerase and terminates the growing RNA chain. It is combined with an NS5A inhibitor such as daclatasvir or velpatasvir. These direct-acting antivirals cure (sustained virological response) well over 90% of patients, including those with genotype 3, the commonest in Pakistan.
HCV direct-acting antivirals
Sofosbuvir: NS5B polymerase
Daclatasvir: NS5A
12 weeks, cure over 90%
Genotype 3 common in Pakistan
Remember Sofosbuvir stops the HCV polymerase.
Exam trap Check for hepatitis B before HCV treatment; HBV can flare when HCV is cleared.
Why the other options are wrong
NS3/4A serine protease NS3/4A is the target of protease inhibitors such as glecaprevir.
NS5A replication complex protein NS5A is the target of daclatasvir, the partner drug.
Reverse transcriptase HCV is an RNA virus without reverse transcriptase.
Viral neuraminidase Neuraminidase is an influenza target.
A 50-year-old woman with primary Sjögren syndrome has a very dry mouth that makes eating difficult, despite saliva substitutes. Which of the following drugs can stimulate her remaining salivary gland function?
Answer: Oral pilocarpine
Salivary secretion is driven by parasympathetic nerves acting on M3 muscarinic receptors of acinar cells. Pilocarpine is a muscarinic agonist that stimulates any surviving glandular tissue to secrete saliva (and tears) in Sjögren syndrome or after head and neck radiotherapy. Expected adverse effects are sweating, flushing, urinary frequency and diarrhoea; it is used cautiously in asthma, heart disease and narrow-angle glaucoma. Antimuscarinic drugs such as hyoscine and amitriptyline worsen dryness.
Pilocarpine
Muscarinic (M3) agonist
Stimulates residual salivary tissue
Uses: Sjögren, post-radiotherapy, glaucoma
Adverse: sweating, flushing, frequency
Remember To make a gland work, stimulate M3.
Exam trap Review the drug list first; many drugs with antimuscarinic action cause dry mouth.
Why the other options are wrong
Oral hyoscine An antimuscarinic; makes the mouth drier.
Amitriptyline Anticholinergic; worsens dry mouth.
Hydroxychloroquine Helps joint and skin features, not gland dryness.
Oral prednisolone Does not restore salivary flow in established disease.
Question 6Hard
In a district hospital, a 58-year-old man with an anterior STEMI is given streptokinase because primary PCI is not available. Twenty minutes into the infusion his blood pressure falls from 130/80 to 85/50 mmHg. He has no wheeze, rash or bleeding, and the ECG shows sinus rhythm at 90/min. The most likely cause of the fall in pressure is:
Hypotension is common during streptokinase infusion and is related to the infusion rate. Plasmin generated in the blood activates the kallikrein system, releasing bradykinin, which dilates vessels. It usually responds to slowing or pausing the infusion, raising the legs and giving fluid. True anaphylaxis is uncommon and would bring wheeze or rash, while the Bezold–Jarisch reflex causes bradycardia, usually with inferior infarcts.
Streptokinase side effects
Hypotension: rate-related, bradykinin
Allergy: fever, rash, rarely anaphylaxis
Antibodies form: do not repeat
Bleeding
Remember Streptokinase low BP: slow the drip, raise the legs.
Exam trap Do not label the patient as allergic to streptokinase from a rate-related fall in pressure alone.
Why the other options are wrong
IgE-mediated anaphylaxis to streptokinase No wheeze, rash or angioedema.
Bezold–Jarisch reflex from reperfusion That gives bradycardia, mainly in inferior MI.
Free-wall rupture with tamponade Rupture is a later complication, typically days 3–5.
Neutralising antistreptococcal antibodies Antibodies cause treatment failure, not acute hypotension.
Question 7Medium
A 19-year-old man has had recurrent 2-day attacks of fever with abdominal and chest pain since childhood. A cousin had similar attacks and died of renal failure. Which daily drug prevents both the attacks and secondary amyloidosis?
Answer: Colchicine
Familial Mediterranean fever is an autosomal recessive autoinflammatory disease caused by MEFV (pyrin) mutations. Uncontrolled inflammasome activity causes short attacks of fever with serositis and a high acute-phase response. Repeated high serum amyloid A levels lead to AA amyloidosis, mainly of the kidney. Daily colchicine reduces neutrophil activation and prevents both attacks and amyloid.
Familial Mediterranean fever
MEFV (pyrin) mutation
Short attacks of fever + serositis
Risk: AA amyloid of the kidney
Daily colchicine prevents both
Remember FMF: colchicine every day.
Exam trap Stopping colchicine between attacks raises the amyloid risk.
Why the other options are wrong
Prednisolone Not effective for long-term prevention.
Allopurinol Used for gout, not FMF.
Ibuprofen Treats pain only.
Methotrexate Not standard prophylaxis for FMF.
Question 8Medium
A woman with regular 28-day cycles takes levonorgestrel 1.5 mg 30 hours after unprotected intercourse on day 12. Which of the following is its main mechanism of action?
Answer: Delays or prevents ovulation
Sperm can survive in the female tract for up to 5 days, so pregnancy needs ovulation during that time. Levonorgestrel given before the LH surge blunts or delays the surge, so no egg is released while sperm are still alive. It has no proven effect on implantation and does not end an established pregnancy. It therefore fails if ovulation has already happened, which is why the copper IUD is more effective.
Emergency contraception
Levonorgestrel: delays ovulation
Works only before the LH surge
No effect on implantation
Copper IUD is most effective
Remember Hormonal EC stops the egg, not the embryo.
Exam trap Hormonal emergency contraception is not an abortifacient.
Why the other options are wrong
Prevents implantation of the embryo No good evidence for this action.
Causes the early embryo to detach It does not disrupt an implanted pregnancy.
Kills sperm in the uterine tubes It does not kill sperm.
Thins the endometrium for months Its effect is short-lived.
Question 9Medium
A woman in preterm labour is given a β2-agonist infusion, and her contractions weaken. The drug raises cAMP in myometrial cells. Which action of protein kinase A then relaxes the muscle?
Answer: Phosphorylates and inhibits MLCK
β2-receptors couple to Gs, raising cAMP and activating protein kinase A. PKA phosphorylates myosin light-chain kinase, reducing its affinity for calcium–calmodulin, so myosin is less phosphorylated and cross-bridge cycling falls. PKA also lowers intracellular calcium by promoting its uptake and extrusion. The net result is smooth muscle relaxation, as in bronchi.
β2 relaxation of smooth muscle
β2: Gs, cAMP
PKA activated
PKA inhibits MLCK
Less calcium, relaxation
Remember cAMP relaxes smooth muscle by disabling MLCK.
Exam trap β2-agonist tocolytics cause tachycardia, hyperglycaemia and hypokalaemia.
Why the other options are wrong
Opens L-type calcium channels Would increase calcium and contraction.
Activates phospholipase C Gq pathway; promotes contraction.
Releases calcium from the SR Would promote contraction.
Inhibits myosin phosphatase Would increase contraction.
Question 10Medium
A woman who is breastfeeding her 6-day-old baby has a lower urinary tract infection. The baby is jaundiced and his G6PD status is not known, and she is worried about drugs getting into her milk. Which antibiotic is the safest choice?
Answer: Cefalexin
Cephalosporins such as cefalexin pass into milk only in small amounts and are considered compatible with breastfeeding. Sulphonamides (co-trimoxazole) can displace bilirubin and cause haemolysis in G6PD deficiency, so they are avoided with a jaundiced newborn. Nitrofurantoin is usually acceptable but is avoided in babies under a month with possible G6PD deficiency. Chloramphenicol risks marrow toxicity, and quinolones are generally avoided if a safer option exists.
UTI while breastfeeding
Beta-lactams are safe in milk
Sulphonamides displace bilirubin
Nitrofurantoin: caution with G6PD in neonate
Avoid chloramphenicol
Remember Penicillins and cephalosporins: safe for the feeding baby.
Exam trap Drugs fine in older babies may be risky in a jaundiced newborn.
Why the other options are wrong
Ciprofloxacin Usually avoided while alternatives exist.
Co-trimoxazole Displaces bilirubin; haemolysis in G6PD deficiency.
Chloramphenicol Risk of marrow toxicity in the infant.
Nitrofurantoin Avoided under 1 month when G6PD deficiency is possible.
Question 11Medium
A woman develops more acne and greasy skin after changing to a progestogen-only pill containing levonorgestrel. What property of this progestogen explains the effect?
Answer: Mildly androgenic 19-nortestosterone
Levonorgestrel and norethisterone are derived from 19-nortestosterone and keep some affinity for the androgen receptor. They also lower SHBG, raising free testosterone. In some women this causes acne, greasy skin or hirsutism. Combined pills partly offset this because ethinylestradiol raises SHBG, while progestogens such as drospirenone or cyproterone are anti-androgenic.
Androgenic progestogens
Levonorgestrel, norethisterone
Derived from 19-nortestosterone
Some androgen receptor activity
Lower SHBG: more free testosterone
Remember Testosterone-derived progestogen can cause acne.
Exam trap The same androgenic quality is why levonorgestrel pills have a lower clot risk.
Why the other options are wrong
It raises sex hormone-binding globulin Levonorgestrel lowers, rather than raises, SHBG.
It acts as an oestrogen receptor agonist It is a progestogen, not an oestrogen agonist.
It blocks androgen receptors in the skin Anti-androgenic action belongs to cyproterone and drospirenone.
It increases adrenal cortisol secretion It does not increase cortisol.
Question 12Easy
A woman in labour at 39 weeks had Streptococcus agalactiae grown from a vaginal swab at 36 weeks. She has no drug allergies. Which antibiotic is given intravenously during labour to protect the baby?
Answer: Benzylpenicillin
Group B streptococcus is a leading cause of early-onset neonatal sepsis, acquired during birth from the colonised genital tract. Intrapartum IV benzylpenicillin, started as soon as possible in labour and ideally at least 4 hours before delivery, reaches high levels in fetal blood and amniotic fluid and reduces colonisation and early infection. GBS remains uniformly sensitive to penicillin. Metronidazole has no activity against streptococci, and doxycycline is avoided in pregnancy.
Group B streptococcus
Cause of early-onset neonatal sepsis
Give IV benzylpenicillin in labour
Ideally ≥4 hours before birth
Penicillin allergy: cefuroxime or clindamycin
Remember GBS in labour: penicillin through the drip.
Exam trap Antibiotics given before labour do not prevent recolonisation at birth.
Why the other options are wrong
Metronidazole Covers anaerobes, not streptococci.
Gentamicin Poor activity against GBS alone.
Nitrofurantoin Urinary antiseptic only.
Doxycycline Tetracyclines are avoided in pregnancy.
