Common side effects

Groups of side effects

• Anticholinergic: dilated pupils, blurred vision, dry mouth, flushed skin, urinary retention, constipation
  • Tricyclic antidepressants, antihistamines, hyoscine, atropine, antipsychotics, incontinence medications
• Antihistaminergic: weight gain, sedation
  • Tricyclic antidepressants, antipsychotics, antihistamines
• Anti-α-adrenergic: postural hypotension, sexual dysfunction, nasal congestion, headache
  • Tricyclic antidepressants, antipsychotics, α-blockers
• Antidopaminergic: extrapyramidal side effects (e.g. tardive dyskinesias, parkinsonism), hyperprolactinaemia (→ galactorrhoea, oligomenorrhea, subfertility), neuroleptic malignant syndrome, oculogyric crisis
  • Metoclopramide, antipsychotics

Side effects to memorise 

TB drugs

• Rifampicin: orange-red tears/urine + hepatitis
• Isoniazid: neuropathy + hepatitis
• Pyrazinamide: + hepatitis
• Ethambutol: optic neuritis

Antiepileptics

• Phenytoin: toxicity (→ cerebellar syndrome), acne, coarse face, gum hypertrophy, hirsutism + inhibit COCP
• Carbamazepine: rash, dizziness, hyponatraemia, hair thinning  + inhibit COCP
• Sodium valproate: tremor, weight gain, hair thinning + teratogenic (avoid if child-bearing age)
• Lamotrigine: rash (Stevens-Johnson syndrome)

Antidepressants

• SSRI (e.g. fluoxetine, citalopram, sertraline): nausea, low libido, withdrawal, insomnia, hyponatraemia
• Tricyclic antidepressant (e.g. amitriptyline): [anticholinergic effects], [antihistaminergic effects], [anti-α-adrenergic effects], hyponatraemia (SIADH), arrhythmias
• Monoamine oxidase A inhibitors (e.g. selegiline): 3Hs – Hypertension, Hepatocellular jaundice, Hyperthermia

Antihypertensives

• ACE inhibitors: dry cough, postural hypotension, acute kidney injury in renal artery stenosis (check U&Es before and 2 weeks after starting), angioedema of the tongue, hyperkalaemia, profound hypotension when started
• Ca²⁺ blocker: pedal oedema, headache/flushing/dizziness
• β-blocker: diabetes risk, impotence, bradycardia, fatigue, cold hands and feet, sleep disturbance
• α-blocker: [anti-α-adrenergic effects]

Diuretics

• ALL: dehydration, hypotension, hyperuricaemia, hypokalaemia (except K+ sparing), hyponatraemia, hypomagnesaemia
• Loop: hypocalcaemia (used in treatment of hypercalcaemia)
• Thiazide (e.g. indapamide): hypercalcaemia
• K+ sparing: hyperkalaemia, gynaecomastia

Hypoglycaemics

• Insulin: hypoglycaemia, fat-hypertrophy at injection site, hypokalaemia (used in treatment of hyperkalaemia), weight gain
• Metformin: weight loss, lactic acidosis, metallic taste, GI disturbance, B₁₂ deficiency
• Sulphonylureas (e.g. gliclazide): hypoglycaemia, weight gain
• Thiazolidinediones (glitazones, e.g. pioglitazone): fluid retention (→ heart failure, oedema), hepatotoxicity, fractures
• DPP4-inhibitors (gliptins, e.g. sitagliptin): pancreatitis
• SGLT2-inhibitors (flozins, e.g. empagliflozin): UTIs/thrush, risk of DKA, weight loss, may increase risk of amputations

Contraception

See here.

Antipsychotics

• ALL: [antidopaminergic effects], [anticholinergic effects], [antihistaminergic effects], [anti-α-adrenergic effects]
• Clozapine: agranulocytosis
• Chlorpromazine: cholestatic jaundice
• Haloperidol: prolonged QT interval, interference with temperature regulation

Antiarrhythmics

• Amiodarone: thyroiditis, pulmonary fibrosis, peripheral neuropathy, myopathy, blue-grey skin pigmentation/photosensitivity, hepatitis, metallic taste
• Digoxin toxicity: xanthopsia (yellow/orange tinge to vision), GI distress, any arrhythmia
• Adenosine: flushing, sense of impending doom

Others

• Lithium: toxicity (tremor/ataxia/dysarthria → coma, convulsions, hypotension), diarrhoea, hypothyroidism, diabetes insipidus
• Steroids: diabetes risk, cushingoid appearance, psychosis, osteoporosis, hypokalaemia, hyperglycaemia, infections, leukocytosis, risk of avascular necrosis
• Azathioprine: myelosuppression
• Ciclosporin: tremor, chronic interstitial nephritis, hypertrichosis, gum hyperplasia, burning sensation in hands/feet
• Levodopa: nausea, red urine/other body fluids, postural hypotension, dyskinesias, ‘on-off’ and ‘wearing off’ effects
• Proton pump inhibitor: tinnitus, GI disturbance, headache, hyponatraemia, hypomagnesaemia

Drugs causing…

Electrolyte imbalances

• Hypernatraemia: sodium-containing antibiotics/fluids, sodium bicarbonate, drugs causing diabetes insipidus (e.g. lithium)
• Hyponatraemia: antidepressants, diuretics, chlorpromazine, carbamazepine, proton pump inhibitors, ACE inhibitors
• Hyperkalaemia: K⁺ sparing diuretics, ACE inhibitors/angiotensin receptor blockers, NSAIDs, trimethoprim, ciclosporin/tacrolimus, heparin

• Hypokalaemia: salbutamol (used in Tx of hyperkalaemia), insulin, diuretics (except K⁺ sparing), caffeine/theophylline
• Hypercalcaemia: thiazide diuretics, lithium
• Hypocalcaemia: loop diuretics, bisphosphonates, phenytoin

Organ toxicity

• Hepatitis: TB antibiotics (rifampicin/isoniazid/pyrazinamide), sodium valproate, methotrexate, amiodarone, statins, paracetamol, phenytoin, ketoconazole/fluconazole, nitrofurantoin, sulfonylureas/sulfonamides
• Cholestasis: co-amoxiclav (may be delayed/severe), clarithromycin/erythromycin, carbamazepine, chlorpromazine, contraceptives, flucloxacillin, sulfonylureas/sulfonamides
• Pulmonary toxicity/fibrosis: nitrofurantoin, amiodarone, methotrexate, cyclophosphamide, sulfasalazine, bleomycin
• Renal impairment
  • Interstitial nephritis: NSAIDS, penicillins/cephalosporins, calcineurin inhibitors (ciclosporin/tacrolimus), PPIs 
  • Acute tubular necrosis: lithium, contrast, gentamicin, amphotericin B
  • Precipitate renal artery stenosis: ACE inhibitors
  • Glomerular damage: NSAIDs
• Creatinine rise: trimethoprim, cimetidine/ranitidine             
• Photosensitivity: tetracyclines, terbinafine, chlorpromazine, amiodarone (→ blue/grey discoloration), chemo (vincristine), ciprofloxacin, psoralens, retinoids, thiazide diuretics, sulphonylureas
• Hypothyroidism: amiodarone, carbimazole, lithium, propylthiouracil, radio-iodine

Other reactions

• Stevens-Johnson syndrome/erythroderma: sulphur-based drugs (sulphonamides, sulfonylureas), antiepileptics, allopurinol, antibiotics
• Vasculitis: allopurinol, penicillin, sulphonamides, thiazides, phenytoin, cephalosporins 
• Agranulocytosis: C’s – Carbamazepine, Clozapine, Colchicine, Carbimazole, Cytotoxic agents
• Gynaecomastia: Digoxin, Spironolactone, Cimetidine, Oestrogens, Tricyclic antidepressants
• Neuropathy: metronidazole, nitrofurantoin, isoniazid, vincristine, cisplatin, amiodarone, phenytoin
• Megaloblastic anaemia: methotrexate, phenytoin, ethanol, trimethoprim, sulfonamides, sodium valproate, metformin, antidepressants
• Dyskinesia: dopaminergic drugs (levodopa, bromocriptine), dopamine-blocking drugs (antipsychotics), antidepressants
• Clostridium difficile risk: cephalosporins, clindamycin, ciprofloxacin, broad spectrum penicillins

Here’s a couple relevant OSCE prescribing stations

1. Medication review
2. Antidepressant counselling
3. Find more here!