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PH9.1-7 | Miscellaneous Therapeutics — Graded Quiz
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A 35-year-old woman with lupus nephritis is on mycophenolate mofetil (MMF). She becomes pregnant. Which statement is MOST accurate?
Correct. MMF is teratogenic and contraindicated in pregnancy. Planned switch to azathioprine well before conception is the standard approach.
MMF (IMPDH inhibitor) is teratogenic (craniofacial malformations, limb defects) and must be stopped ≥6 weeks before conception. Azathioprine (purine analogue) is the preferred immunosuppressant for lupus in pregnancy. Tacrolimus is also relatively safer. MMF/sirolimus are Category D/X.
Incorrect. MMF is a known human teratogen. It must be stopped and replaced with a pregnancy-compatible immunosuppressant (azathioprine) before conception.
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Pralidoxime (PAM) is used in organophosphate poisoning. Which statement about PAM is CORRECT?
Correct. The time-sensitivity of PAM is its critical limitation — enzyme ageing makes it ineffective if delayed. Early administration is essential.
Pralidoxime (an oxime) breaks the phosphorylated-AChE bond and restores enzyme activity. This must happen before 'ageing' — the irreversible conformational change in phosphorylated AChE (typically within 24–48 hours for most OPs, much faster for some compounds like soman). Once aged, PAM is ineffective. Atropine is given first; PAM is concurrent/following.
Incorrect. PAM's efficacy is time-critical due to ageing of the phosphorylated enzyme. Atropine precedes PAM.
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A 4-year-old child from a mining community has blood lead level of 52 µg/dL without encephalopathy. The MOST appropriate chelation therapy is:
Correct. DMSA (succimer) is the first-line oral chelator for paediatric lead poisoning without encephalopathy. It is given orally, which simplifies outpatient management.
Succimer (2,3-dimercaptosuccinic acid; DMSA) is the preferred oral chelator for paediatric lead poisoning at blood lead levels 45–70 µg/dL without encephalopathy. It is safe, oral, and well-tolerated in children. CaNa₂EDTA may also be used but requires IV administration. BAL is reserved for lead encephalopathy (given with CaNa₂EDTA). D-penicillamine is for Wilson's disease.
Incorrect. For a child with lead poisoning without encephalopathy, succimer (DMSA) is preferred. BAL is reserved for encephalopathy, and D-penicillamine for Wilson's disease.
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Which vaccine requires strict cold chain conditions between -15°C and -25°C (ultra-cold chain) for storage?
Correct. mRNA vaccines have the most demanding cold chain requirements due to mRNA instability at room temperature. This was a major logistical challenge in COVID-19 vaccination programmes globally.
mRNA vaccines are highly temperature-sensitive due to mRNA instability — the Pfizer-BioNTech vaccine initially required -70°C storage; updated formulations require -15 to -25°C. OPV requires 2–8°C (sensitive to heat, not needing ultra-cold). BCG and DPT require 2–8°C standard cold chain. Understanding cold chain requirements is essential for national immunisation programme management (PH9.4).
Incorrect. mRNA vaccines (like BNT162b2) require ultra-cold storage. The other vaccines listed all require standard cold chain (2–8°C).
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Chlorine-releasing compounds (e.g. sodium hypochlorite, bleach) are commonly used for environmental surface disinfection. What concentration is recommended for blood spill decontamination in healthcare settings?
Correct. Blood spills require 0.5% sodium hypochlorite (5000 ppm). Organic matter inactivates hypochlorite, so a higher working concentration is needed compared to routine surface cleaning.
Blood spills require a higher bleach concentration (0.5%, 5000 ppm available chlorine) than routine surface disinfection (0.05–0.1%, 500–1000 ppm). Higher concentration compensates for organic matter (blood) which inactivates hypochlorite. The spill area should first be covered with absorbent material, then flooded with 0.5% bleach for ≥10 minutes contact time.
Incorrect. Blood spill disinfection requires 0.5% (5000 ppm) bleach — higher than routine surface concentration — to compensate for inactivation by organic matter.
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A patient with moderate plaque psoriasis is started on methotrexate. Which laboratory test is MOST important to monitor on a regular basis throughout treatment?
Correct. CBC (for myelosuppression) and LFTs (for hepatotoxicity) are the mandatory monitoring parameters for methotrexate therapy in psoriasis.
Methotrexate's two main dose-related toxicities are: (1) bone marrow suppression (CBC: cytopenias — worst risk with concomitant NSAIDs or sulfonamides) and (2) hepatotoxicity (LFTs: elevations signal toxicity; cumulative doses >1.5 g increase cirrhosis risk). Renal function is also monitored as MTX is renally excreted. Leucovorin supplementation prevents mucositis. Folic acid 5 mg weekly (not on MTX day) reduces side effects.
Incorrect. The critical toxicities are haematological (bone marrow suppression) and hepatic (hepatotoxicity/fibrosis). CBC and LFTs are both mandatory.
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A 70-year-old man with COPD develops open-angle glaucoma. Which class of anti-glaucoma drug should be AVOIDED in this patient?
Correct. Timolol is a non-selective beta-blocker. Even topical eye drops can be absorbed systemically sufficient to precipitate bronchospasm in COPD or asthma. Prostaglandin analogues are the preferred first-line drug in this patient.
Topical timolol (non-selective beta-blocker) is absorbed systemically and can cause bronchoconstriction in COPD/asthma patients by blocking beta-2 receptors in bronchial smooth muscle — even small amounts absorbed through the conjunctiva. Prostaglandin analogues, alpha-2 agonists, and topical CAIs can be used with caution. Punctal occlusion reduces systemic absorption of timolol if it must be used.
Incorrect. Topical beta-blockers (timolol) are contraindicated in obstructive airway disease due to systemic absorption causing bronchospasm.
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A health worker sustains a needlestick injury from a patient known to have hepatitis B. The health worker has no prior hepatitis B vaccination. What is the CORRECT immediate management?
Correct. The dual strategy (HBIG + vaccine) exploits passive immunity for immediate cover while active immunity from the vaccine develops over weeks. HBIG alone wanes; vaccine alone takes too long.
This question tests PH9.4 (vaccine types and passive immunity). For hepatitis B post-exposure in an unvaccinated individual: HBIG (hepatitis B immunoglobulin — passive, immediate, temporary protection) must be given within 24 hours TOGETHER WITH the first dose of HBV vaccine (to initiate active, lasting immunity). HBIG alone is insufficient for long-term protection; vaccine alone is too slow. This is the classic combined active-passive immunisation example.
Incorrect. Unvaccinated needlestick victims from HBsAg-positive sources require both immediate HBIG (passive immunity) and HBV vaccine series (active immunity).
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Tacrolimus and cyclosporine both inhibit calcineurin. Which of the following distinguishes tacrolimus from cyclosporine?
Correct. Cyclosporine binds cyclophilin; tacrolimus binds FKBP12. Tacrolimus causes fewer cosmetic side effects but more diabetes — a key distinction for drug selection.
Mechanism: Cyclosporine binds cyclophilin; tacrolimus binds FKBP12. Both drug-protein complexes then inhibit calcineurin, blocking IL-2 transcription. Tacrolimus is 10–100× more potent. Adverse effect profile differs: tacrolimus has LESS gingival hyperplasia, hirsutism, dyslipidaemia than cyclosporine but MORE post-transplant diabetes mellitus (PTDM) and neurotoxicity. Both require TDM (narrow TI). Both cause nephrotoxicity to similar degrees.
Incorrect. The binding proteins are reversed — cyclosporine binds cyclophilin, tacrolimus binds FKBP12. Tacrolimus is more potent with a different (not uniformly worse) side effect profile.
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Benzodiazepine overdose presents with sedation, respiratory depression, and ataxia. The specific reversal agent is:
Correct. Flumazenil competitively antagonises GABA-A BZD binding sites, reversing sedation, amnesia, and respiratory depression. The short half-life means resedation monitoring is important.
Flumazenil is the competitive benzodiazepine antagonist at GABA-A receptors. It rapidly reverses BZD-induced CNS depression. Its half-life is short (1 hour) — resedation can occur if acting on a long-acting BZD. It can precipitate withdrawal seizures in BZD-dependent patients. Naloxone reverses opioids; physostigmine reverses anticholinergics; protamine reverses heparin anticoagulation.
Incorrect. Flumazenil is the BZD-specific antidote. Naloxone is for opioids; physostigmine for anticholinergic toxicity; protamine for heparin.
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