Safety
Contraindications & interactions
Know when a drug must be avoided, why, and what to choose instead — then check any two drugs together.
| Drug | Contraindicated in | Reason | Alternative |
|---|---|---|---|
| Aspirin | Children with viral fever | Risk of Reye's syndrome | Paracetamol |
| NSAIDs (Ibuprofen, Diclofenac) | Peptic ulcer | COX-1 inhibition reduces protective prostaglandins | Paracetamol or Celecoxib with PPI |
| Propranolol | Bronchial asthma | β2 blockade causes bronchospasm | Atenolol (cautiously) or CCB |
| ACE inhibitors (Enalapril) | Pregnancy | Fetal renal damage and malformations | Methyldopa, Labetalol, Nifedipine |
| ACE inhibitors | Bilateral renal artery stenosis | Precipitates acute renal failure | Calcium channel blocker |
| Tetracyclines (Doxycycline) | Pregnancy & children < 8 yr | Teeth discolouration, bone growth inhibition | Azithromycin / Amoxicillin |
| Fluoroquinolones | Children & pregnancy | Damage to weight-bearing cartilage | Cephalosporins |
| Metformin | Renal failure (eGFR < 30) | Risk of lactic acidosis | Insulin or DPP-4 inhibitor |
| Pioglitazone | Heart failure | Fluid retention worsens failure | SGLT2 inhibitor |
| Morphine | Head injury | Raises intracranial pressure, masks pupillary signs | Non-opioid analgesics |
| Morphine | Bronchial asthma | Histamine release and respiratory depression | Tramadol (cautiously), NSAIDs |
| Atropine | Angle-closure glaucoma | Mydriasis blocks aqueous outflow | Glycopyrrolate (peripheral) |
| Spironolactone | Hyperkalaemia, renal failure | Further K⁺ retention | Thiazide or loop diuretic |
| Warfarin | Pregnancy | Teratogenic (fetal warfarin syndrome) | Heparin / LMWH |
| Sodium valproate | Pregnancy, hepatic disease | Neural tube defects, hepatotoxicity | Lamotrigine, Levetiracetam |
| Haloperidol | Parkinsonism | D2 blockade worsens extrapyramidal symptoms | Quetiapine / Clozapine |
| Metoclopramide | GI obstruction, epilepsy | Prokinetic action; lowers seizure threshold | Ondansetron |
| Chloramphenicol | Neonates | Gray baby syndrome | Cefotaxime |
| Primaquine | G6PD deficiency, pregnancy | Haemolytic anaemia | Chloroquine (no radical cure) |
| Glucocorticoids (long term) | Peptic ulcer, active TB, diabetes | Impair healing, immunosuppression, hyperglycaemia | Steroid-sparing agents |
| Methotrexate | Pregnancy | Abortifacient and teratogenic | Hydroxychloroquine, Sulfasalazine (RA) |
| Lithium | Renal disease, sodium restriction | Narrow therapeutic index; toxicity | Valproate |