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Systemic retinoid (Vitamin A derivative) / Anti-acne Pregnancy: ABSOLUTELY CONTRAINDICATED. Category X. Causes major malformations in virtually all fetuses.

Isotretinoin

Brand names: Roaccutane, Rizuderm

Adult dose

Dose: 0.5 mg/kg/day initially; usual range 0.5–1 mg/kg/day; cumulative dose target 120–150 mg/kg
Route: Oral (with food — improves absorption)
Frequency: Once or twice daily
Max: 1 mg/kg/day (standard); up to 2 mg/kg/day in severe recalcitrant cases
Start 0.5 mg/kg/day for 4 weeks. If no significant side effects, may increase to 1 mg/kg/day. Typical course 4–8 months to reach cumulative target of 120–150 mg/kg (minimum 4 months). Acne may flare initially.

Paediatric dose

Dose: 0.5 mg/kg
Route: Oral
Frequency: Once daily
Max: 1 mg/kg/day
≥12 years (licensed): same weight-based dosing as adults. Cumulative dose 120–150 mg/kg applies equally. Regular monitoring as for adults. Tetracyclines contraindicated in <12 years (avoid prescribing concurrently regardless of age).

Dose adjustments

Renal

No dose adjustment required.

Hepatic

Avoid in severe hepatic impairment; monitor LFTs.

Paediatric weight-based calculator

≥12 years (licensed): same weight-based dosing as adults. Cumulative dose 120–150 mg/kg applies equally. Regular monitoring as for adults. Tetracyclines contraindicated in <12 years (avoid prescribing concurrently regardless of age).

Clinical pearls

  • Pregnancy Prevention Programme: pregnancy test before, monthly during, 5 weeks after; 2 forms of contraception
  • Not prescribable without REMS/PGP compliance (GPP/Pregnancy Prevention Programme in UK)
  • Initial acne flare common (weeks 1–4) — advise patient
  • Depression monitoring: NICE recommends asking about mood at each visit
  • Avoid waxing, dermabrasion, laser while on isotretinoin (skin fragile — delayed healing)

Contraindications

  • Pregnancy (Category X — extremely teratogenic)
  • Women of childbearing potential without Pregnancy Prevention Programme compliance
  • Breastfeeding
  • Vitamin A supplementation
  • Tetracycline co-prescription (raised ICP risk)
  • Severe hyperlipidaemia

Side effects

  • Dry skin, lips, mucous membranes (universal — manage with emollients)
  • Teratogenicity (major — must not become pregnant during or 1 month after)
  • Depression and suicidality (contested — monitor)
  • Myalgia and arthralgia
  • Elevated triglycerides and LDL
  • Elevated LFTs
  • Photosensitivity
  • Night blindness
  • Pseudotumor cerebri (especially with tetracyclines)

Interactions

  • Tetracyclines — contraindicated (raised intracranial pressure)
  • Vitamin A supplements — avoid (additive toxicity)
  • Progestin-only contraceptives — reduced efficacy (use 2 methods)
  • St John's Wort — may reduce contraceptive pill efficacy

Monitoring

  • Pregnancy tests (monthly)
  • Fasting lipids
  • LFTs
  • FBC
  • Mood assessment

Reference: BNFc; BNF; MHRA Retinoid PPP; BAD Acne Guidelines; NICE CG184. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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