Systemic retinoid (Vitamin A derivative) / Anti-acne Pregnancy: Absolutely contraindicated in pregnancy. Isotretinoin is a powerful human teratogen inducing a high frequency of severe and life-threatening birth defects — central nervous system abnormalities (hydrocephalus, cerebellar malformation, microcephaly), facial dysmorphia, cleft palate, external ear and eye abnormalities, cardiovascular abnormalities, and thymus and parathyroid gland abnormalities — with an increased incidence of spontaneous abortion. Women of childbearing potential must comply with the Pregnancy Prevention Programme and use effective contraception one month before, during, and up to one month after treatment. If pregnancy occurs, treatment must be stopped and the patient referred to a physician specialised or experienced in teratology. Contraindicated during breast-feeding. Isotretinoin in therapeutic dosages does not affect sperm number, motility or morphology in men. (US label: Pregnancy Category X.)

Isotretinoin

Brand names: Roaccutane, Rizuderm

Isotretinoin is an oral retinoid used by specialists for severe or treatment-resistant acne; it can produce long-lasting remission.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Start at 0.5 mg/kg daily. For most patients the dose ranges from 0.5-1.0 mg/kg per day, adjusted individually according to therapeutic response and adverse effects.

Route: Oral — capsules taken with food

Frequency: Once or twice daily

Max: 'It has been shown that no substantial additional benefit is to be expected beyond a cumulative treatment dose of 120-150 mg/kg.' No maximum single daily dose is stated in the UK SPC.

Source: eMC SPC for Isotretinoin 10 mg capsules, soft. PRESCRIBING RESTRICTION: 'Isotretinoin should only be prescribed by or under the supervision of physicians with expertise in the use of systemic retinoids for the treatment of severe acne and a full understanding of the risks of isotretinoin therapy and monitoring requirements.' The therapeutic response and some adverse effects are dose-related and vary between patients, necessitating individual dosage adjustment during therapy. DURATION: long-term remission and relapse rates are more closely related to the total dose administered than to either duration of treatment or daily dose; a treatment course of 16-24 weeks is normally sufficient to achieve remission, and in the majority of patients complete clearing is obtained with a single course. RETREATMENT: in the event of a definite relapse a further course may be considered using the same daily dose and cumulative treatment dose; because further improvement can be observed up to 8 weeks after discontinuation, a further course should not be considered until at least this period has elapsed. INTOLERANCE: in patients who show severe intolerance to the recommended dose, treatment may be continued at a lower dose, accepting a longer therapy duration and a higher risk of relapse; the dose should normally be continued at the highest tolerated dose. PREGNANCY PREVENTION PROGRAMME: isotretinoin is a powerful human teratogen and is contraindicated in women of childbearing potential unless all conditions of the Pregnancy Prevention Programme are met — effective contraception without interruption for 1 month before, throughout treatment and for 1 month after, with regular pregnancy testing and monthly follow-up. PAEDIATRIC: 'Isotretinoin should not be used for the treatment of prepubertal acne and is not recommended in children less than 12 years of age due to a lack of data on efficacy and safety.' The SPC dose heading is 'Adults including adolescents and the elderly', so adolescents aged 12 and over are dosed as adults. §4.4 and §4.8 are marked truncated at the source-fetch limit and eMC §4.5 was not included in this bundle.

Paediatric dose

Dose: 0.5 mg/kg

Route: Oral, with food

Frequency: Daily (given once or twice daily), as the starting dose; usual range 0.5-1.0 mg/kg per day

Max: Cumulative treatment dose of 120-150 mg/kg — no substantial additional benefit is expected beyond this

This is the ADULT starting dose applied to adolescents: the SPC posology heading is 'Adults including adolescents and the elderly: Isotretinoin therapy should be started at a dose of 0.5 mg/kg daily.' There is no separate paediatric regimen. Isotretinoin should NOT be used for prepubertal acne and is NOT recommended in children less than 12 years of age due to a lack of data on efficacy and safety. The Pregnancy Prevention Programme applies to all female patients of childbearing potential, including adolescents. Verify against a children's formulary before use.

Dose adjustments

Renal

In patients with severe renal insufficiency treatment should be started at a lower dose (e.g. 10 mg/day). The dose should then be increased up to 1 mg/kg/day or until the patient is receiving the maximum tolerated dose.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION Isotretinoin capsules should be administered with a meal (see PRECAUTIONS: Information for Patients ). The recommended dosage range for isotretinoin capsules are 0.5 to 1 mg/kg/day given in two divided doses with food for 15 to 20 weeks. In studies comparing 0.1, 0.5, and 1 mg/kg/day 8 , it was found that all dosages provided initial clearing of disease, but there was a greater need for retreatment with the lower dosages. During treatment, the dose may be adjusted according to response of the disease and/or the appearance of clinical side effects – some of which may be dose related. Adult patients whose disease is very severe with scarring or is primarily …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-06-26. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Women who are pregnant or breastfeeding
Women of childbearing potential unless all of the conditions of the Pregnancy Prevention Programme are met
Hypersensitivity to isotretinoin or to any of the excipients; the 10 mg product contains refined and partly hydrogenated soya oil, so it is contraindicated in patients allergic to peanut or soya
Hepatic insufficiency; excessively elevated blood lipid values; hypervitaminosis A
Patients receiving concomitant treatment with tetracyclines

Side effects

Very common: dryness of the skin and of the mucosae — cheilitis (lips), nasal dryness and epistaxis, conjunctivitis, dry eye, blepharitis, eye irritation; pruritus, rash erythematous, dermatitis, localised exfoliation, skin fragility; nasopharyngitis
Very common: headache; transaminase increased
Very common: thrombocytopenia, anaemia, thrombocytosis, red blood cell sedimentation rate increased (neutropenia is common; lymphadenopathy rare)
Rare: depression, depression aggravated, anxiety, aggressive tendencies, mood alterations; psychotic disorder, suicidal ideation, suicide attempt and suicide (very rare)
Rare/very rare: benign intracranial hypertension (with papilloedema), convulsions; inflammatory bowel disease, colitis, ileitis, pancreatitis, gastrointestinal and haemorrhagic diarrhoea; hepatitis; anaphylactic reactions and hypersensitivity; vasculitis; bronchospasm particularly in patients with asthma

Interactions

Tetracyclines — concomitant treatment is contraindicated (SPC §4.3, cross-referring to §4.5). The US label adds that concomitant use has been associated with a number of cases of pseudotumor cerebri (benign intracranial hypertension)
Vitamin A — patients should be advised against taking vitamin supplements containing vitamin A, to avoid additive toxic effects (US label)
Micro-dosed progesterone preparations ('minipills' that do not contain an oestrogen) may be an inadequate method of contraception during isotretinoin therapy (US label). NOTE: eMC §4.5 was NOT included in this bundle, so the UK interaction list has not been verified — clinician to source it

Clinical monograph

How it works

It is a vitamin-A derivative that reduces sebum production, normalises follicular keratinisation and has anti-inflammatory effects.

Prescribing in practice

It is highly teratogenic — it must only be used within a Pregnancy Prevention Programme (effective contraception, regular pregnancy testing, limited prescription duration) in those able to become pregnant.
Mucocutaneous dryness (lips, skin, eyes) is near-universal; it raises lipids and liver enzymes and can cause musculoskeletal effects.
Mood changes and (rarely) sexual dysfunction are subject to MHRA monitoring — counsel patients and families to report mood or sexual symptoms.

Monitoring

Check lipids and liver function; in those able to become pregnant follow the Pregnancy Prevention Programme; review mood and skin/mucosal effects.

Counselling the patient

Do not become pregnant — use the required contraception and pregnancy testing; it can severely harm a baby.
Dry lips, skin and eyes are expected — use lip balm and moisturiser; use sun protection.
Report low mood, thoughts of self-harm, or any sexual problems.

Evidence & guidelines

A specialist treatment for severe acne, used within a strict Pregnancy Prevention Programme and MHRA monitoring (NICE NG198).

Reference: MHRA Retinoid PPP; BAD Acne Guidelines; NICE CG184; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways