What does 'drug of choice' mean, and which ones are asked most?
A drug of choice (DOC) is the agent a current guideline or standard reference names as first-line for a specific condition — usually because it works best, acts fastest or has the best safety record. It is not always the only effective drug: in scrub typhus, for example, tetracycline, azithromycin, doxycycline and rifampicin all work, but doxycycline is the usual first choice.
Exam questions test three things: the pairing (condition → drug), the context that changes the answer (pregnancy, allergy, drug resistance, a pre-excited heart), and the next step when the first drug fails. This page groups the high-yield pairs by system, with the exact wording of the current StatPearls chapters so the answer stands up to a challenge.
What is the drug of choice for common infections?
| Condition | Drug of choice | Key detail |
|---|---|---|
| MRSA (most infections in hospitalised patients) | IV vancomycin | Also first-line for MRSA endocarditis; linezolid or clindamycin are alternatives for pneumonia, but not for endocarditis |
| Syphilis (most stages) | Benzathine penicillin G | Organism remains very sensitive to penicillin |
| Neurosyphilis (incl. ocular, otosyphilis) | IV aqueous crystalline penicillin G | 18–24 million units/day for 10–14 days |
| Scrub typhus | Doxycycline | 100 mg IV or oral twice daily for 7–14 days; azithromycin is the alternative (3-day course) |
| Severe malaria | IV or IM artesunate | First-line in all patients, including children and pregnant women in all trimesters; doses at 0, 12 and 24 h |
| Amoebic liver abscess | Metronidazole, then a luminal agent | 500–750 mg three times daily for 7–10 days, followed by paromomycin |
| Pneumocystis jirovecii pneumonia | Trimethoprim-sulfamethoxazole | Also first-line prophylaxis (e.g. HIV with CD4 < 200 cells/µL) |
| Toxoplasmosis | Pyrimethamine + sulfadiazine | The preferred regimen |
| Cholera | Rehydration + a tetracycline | Tetracyclines first-line, macrolides second-line |
| HSV encephalitis | IV acyclovir | 10 mg/kg every 8 hours, started on suspicion |
| Gonorrhoea (uncomplicated) | Ceftriaxone | 500 mg IM single dose (< 150 kg) |
| Typhoid (uncomplicated, empiric) | Azithromycin | Ciprofloxacin only where fluoroquinolone resistance is rare; carbapenem for severe XDR disease |
What is the drug of choice in cardiac and allergic emergencies?
| Condition | Drug of choice | Dose / detail |
|---|---|---|
| Anaphylaxis | Adrenaline (epinephrine) IM | 1:1000, 0.3–0.5 mg IM, plus airway care and a fluid bolus |
| Stable SVT (after failed vagal manoeuvres) | Adenosine | Rapid IV push through a large peripheral vein |
| Torsades de pointes | IV magnesium | 2 g slow IV push, then infusion 1–4 g/h |
| Digoxin-induced dysrhythmia | Digoxin immune Fab | First-line for AV block or VT from digoxin toxicity |
Adenosine blocks adenosine A1 receptors and transiently interrupts conduction through the AV node, breaking the re-entry circuit. Because it is metabolised within seconds it must be given as a rapid push, and its side effects are short-lived.
Which drugs are first-line in endocrine emergencies?
| Condition | Drug of choice | Why / detail |
|---|---|---|
| Thyroid storm | Propylthiouracil (PTU) | Favoured because it also blocks peripheral conversion of T4 to T3; loading 500–1000 mg |
| Thyroid storm — adrenergic symptoms | Propranolol | 40–80 mg every 4–6 h; esmolol in ICU |
| Diabetic ketoacidosis | Isotonic fluid (0.9% saline), then IV regular insulin infusion | Insulin only once potassium is at least 3.5 mmol/L (StatPearls) |
| Prolactinoma | Cabergoline | Normalises prolactin and shrinks the tumour more often than bromocriptine, with fewer side effects |
What is the drug of choice in neurology and psychiatry?
| Condition | Drug of choice | Detail |
|---|---|---|
| Status epilepticus (emergent control) | Benzodiazepine — lorazepam preferred | Lorazepam 0.1 mg/kg IV; diazepam 0.15 mg/kg IV if lorazepam unavailable |
| Status epilepticus (urgent control) | Fosphenytoin, phenytoin, levetiracetam or valproate | Levetiracetam preferred in pregnancy (lower risk of birth defects) |
| Trigeminal neuralgia | Carbamazepine (or oxcarbazepine) | Carbamazepine is the only FDA-approved drug for it |
| Alcohol withdrawal | Benzodiazepines (or phenobarbital) | Plus high-dose parenteral thiamine |
| Treatment-resistant schizophrenia | Clozapine | After two failed antipsychotic trials; also reduces suicidal behaviour |
| Malignant hyperthermia | Dantrolene | 2.5 mg/kg IV immediately, repeated up to 10 mg/kg |
| Neuroleptic malignant syndrome | Stop the offending drug; bromocriptine or dantrolene if refractory | Bromocriptine reverses the hypodopaminergic state |
| Severe lithium toxicity | Haemodialysis | The preferred extracorporeal treatment |
Which drugs of choice change in pregnancy?
| Situation | Drug of choice | Detail |
|---|---|---|
| Eclampsia (prevent and control seizures) | Magnesium sulphate | Loading 6 g IV over 15–20 min, then 2 g/h |
| Severe malaria in pregnancy | IV or IM artesunate | First-line in all trimesters |
| Syphilis in pregnancy with penicillin allergy | Penicillin after desensitisation | Skin test, then desensitise |
| Status epilepticus in pregnancy (urgent control) | Levetiracetam | Lower risk of birth defects than phenytoin, valproate or phenobarbital |
Magnesium sulphate is preferred over other anticonvulsants for preventing eclamptic seizures. It is given mainly to prevent further seizures, not to stop the current one — most eclamptic seizures are self-limiting. It also lowers the risk of maternal death. StatPearls pairs seizure control with magnesium sulphate with timely delivery as the critical steps of immediate management.
What is the antidote of choice for common poisonings?
| Poison | Antidote / treatment of choice | Key detail |
|---|---|---|
| Paracetamol (acetaminophen) | N-acetylcysteine | Start at once if overdose is suspected; give if level is on or above the treatment line |
| Organophosphate | Atropine + pralidoxime | Atropine 2–5 mg IV (adult); pralidoxime works only before 'aging' |
| Methanol | Fomepizole | Ethanol if fomepizole is unavailable; dialysis often needed |
| Cyanide | Hydroxocobalamin | Preferred over the nitrite–thiosulfate combination |
| Digoxin | Digoxin immune Fab | Empiric 10 vials (adult), 5 (child) if dose unknown |
| Methaemoglobinaemia | Methylene blue | If level above 20–30% or the patient is symptomatic |
| Opioids | Naloxone | IV naloxone reverses opioid effects within minutes |
| Lithium (severe) | Haemodialysis | Lithium does not bind to activated charcoal |
Atropine is the primary treatment in organophosphate poisoning: it competes with acetylcholine at muscarinic receptors. Pralidoxime reactivates phosphorylated acetylcholinesterase, but only before the enzyme 'ages'. After that, new enzyme has to be synthesised.
Which drugs of choice have changed because of resistance or newer evidence?
- Typhoid: resistance to all three old first-line drugs (ampicillin, chloramphenicol and co-trimoxazole) appeared in 1972 and was common by the 1980s. Ciprofloxacin is now the drug of choice only where fluoroquinolone resistance is rare. Azithromycin is the empiric choice for uncomplicated illness.
- Gonorrhoea: widespread resistance has made most antibiotic classes ineffective, so ceftriaxone is the main recommended therapy.
- Cyanide: hydroxocobalamin is preferred over the sodium nitrite–thiosulfate pair because its side effects are mostly limited to red discolouration of the skin and urine. Thiosulfate also penetrates the brain poorly.
- DKA insulin: an IV bolus is not needed if an hourly infusion of 0.14 U/kg/h is used. Hourly subcutaneous lispro is an alternative in selected patients.
- Alcohol withdrawal: phenobarbital can now be used alone in place of benzodiazepines, or as rescue therapy.