Common side effects

Prescribing > Adverse drug reactions

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

Learning notes: 246

Stations available: 207

Qbank questions: 2252

Conditions: 558

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Common side effects

Groups of side effects

Side effects to memorise

Drugs causing…

Electrolyte imbalances

Organ toxicity

Other reactions

Here’s a couple relevant OSCE prescribing stations

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Adverse drug reactions