Isotretinoin information from DrugsUpdate  

Pharmacodynamics

Pharmacokinetics

Isotretinoin is a synthetic retinoid which reduces sebaceous gland size and sebum production. It also regulates cell proliferation and differentiation.

Absorption
Low oral bioavailability. Peak plasma concentrations in 1-4 hours (oral).

Distribution
Protein-binding: 99.9%, mainly to albumin.

Metabolism
Hepatic, via CYP450 isoenzyme pathway.

Excretion
Via urine and faeces.

Isotretinoin Indications / Isotretinoin Uses

Information Not Available

Isotretinoin Adverse Reactions / Isotretinoin Side Effects

Dryness of mucous membranes, dryness of skin with scaling, fragility, erythema, cheilitis, pruritus, epistaxis, conjunctivitis, dry sore mouth and palmo-plantar exfoliation. Corneal opacities, dry eyes, visual disturbances, skeletal hyperostosis and musculoskeletal symptoms. Elevation of serum triglycerides, LFTs, ESR and blood glucose. Hair thinning, photosensitivity, changes in skin pigmentation, paronychia. GI disturbances, hepatitis. Headache, drowsiness, sweating, mood changes, psychotic symptoms, depression, suicidal tendencies, benign intracranial hypertension, seizures. Vasculitis, hypersensitivity reactions, IBS.

Potentially Fatal: Anaphylaxis. Haemorrhagic pancreatitis.

Precautions

Special prescribing requirements
Because of isotretinoin's teratogenicity, and to minimize fetal exposure, isotretinoin is approved for marketing only under a restricted distribution program, called iPLEDGE, approved by the FDA. Isotretinoin must be prescribed by prescribers and dispensed by pharmacies registered and activated with the iPLEDGE program, and must only be dispensed to patients who are registered and meet all the requirements of iPLEDGE.

Monitor
Obtain 2 negative urine or serum pregnancy tests prior to receiving initial isotretinoin prescription and negative result for urine or serum pregnancy test each month; obtain pretreatment and follow-up lipids during fasting conditions; monitor liver function weekly or biweekly until isotretinoin response has been established; periodically determine blood glucose.

Special Precautions

Preexisting or predisposition to hypertriglyceridaemia (e.g. DM, obesity or increased alcohol intake). Monitor triglyceride levels. Monitor blood lipids and LFTs at wkly or bi-wkly intervals. Monitor blood glucose in known or suspected DM patients. Genetic predisposition for age-related osteoporosis, history of childhood osteoporosis, osteomalacia or other bone metabolism disorders. Anorexia nervosa. History of psychiatric disorder. May impair night vision. Avoid wax epilation and skin resurfacing procedures for at least 6 mth. Avoid prolonged exposure to UV light or sunlight. Discontinue if hearing impairment, abdominal pain, rectal bleeding, severe diarrhoea or adverse ocular effects occur. Patient should not donate blood during therapy and for at least 1 mth following drug discontinuation.

Other Drug Interactions

Additive toxicity with vitamin A or its derivatives. Decreased efficacy of microdosed progesterone (use 2 forms of contraception). May increase risk of bone loss with phenytoin. May increase risk of osteoporosis with systemic corticosteroids. Reduces plasma levels of carbamazepine.

Potentially Fatal: Increased risk of pseudotumor cerebri with tetracyclines.

Other Interactions

Food Interaction
Avoid or limit ethanol intake. Avoid dong quai, St John's wort.

Dosage

Oral
Acne
Adult: Initially, 0.5-1 mg/kg daily in 2 divided doses. Usual duration of treatment: 15-20 weeks; may be discontinued if number of cysts is reduced by >70% (whichever is sooner). Patients intolerant to initial dose: Continue treatment at a lower dose. Patients with very severe acne or acne evident on the body instead of face: Up to 2 mg/kg daily. There should be a 2-mth drug-free interval if a 2nd course is necessary.
Renal impairment: Dose reduction may be needed.
Hepatic impairment: Dose reduction may be needed.

Topical/Cutaneous
Acne
Adult: As 0.05% gel: Apply sparingly once or twice daily. Effect may not be evident for 6-8 weeks.

Food(before/after)

Should be taken with food

Isotretinoin and Pregnancy

Contraindicated in pregnancy

Category X: Studies in animals or human beings have demonstrated foetal abnormalities or there is evidence of foetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Isotretinoin and Lactation

Contraindicated in lactation

Isotretinoin and Children

Safety and efficacy not established in children younger than 12 years of age. Use with caution in children 12 to 17 years of age, especially in those with known metabolic or structural bone disease.

Isotretinoin and Geriatic

Clinical studies did not include sufficient numbers of subjects aged 65 years and older to determine whether they respond differently from younger subjects.

Isotretinoin and Other Contraindications

Pregnancy, lactation

Storage

Oral
Store at 15-30°C (59-86°F)

Topical/Cutaneous
Store below 25°C (77°F)

Lab interference

Oral
Store at 15-30°C (59-86°F)

Topical/Cutaneous
Store below 25°C (77°F)