Soriatane (Acitretin) - Drug Interactions, Contraindications, Overdosage

DRUG INTERACTIONS

Pharmacokinetic Drug Interactions

(see also boxed CONTRAINDICATIONS AND WARNINGS and PRECAUTIONS: Drug Interactions ): In studies of in vivo pharmacokinetic drug interactions, no interaction was seen between acitretin and cimetidine, digoxin, phenprocoumon or glyburide.

Ethanol

Clinical evidence has shown that etretinate (a retinoid with a much longer half-life, see below) can be formed with concurrent ingestion of acitretin and ethanol. In a two-way crossover study, all 10 subjects formed etretinate with concurrent ingestion of a single 100 mg oral dose of acitretin during a 3-hour period of ethanol ingestion (total ethanol, approximately 1.4 g/kg body weight). A mean peak etretinate concentration of 59 ng/mL (range 22 to 105 ng/mL) was observed, and extrapolation of AUC values indicated that the formation of etretinate in this study was comparable to a single 5 mg oral dose of etretinate. There was no detectable formation of etretinate when a single 100 mg oral dose of acitretin was administered without concurrent ethanol ingestion, although the formation of etretinate without concurrent ethanol ingestion cannot be excluded (see boxed CONTRAINDICATIONS AND WARNINGS). Of 93 evaluable psoriatic patients on acitretin therapy in several foreign studies (10 to 80 mg/day), 16% had measurable etretinate levels (>5 ng/mL).

Etretinate has a much longer elimination half-life compared to that of acitretin. In one study the apparent mean terminal half-life after 6 months of therapy was approximately 120 days (range 84 to 168 days). In another study of 47 patients treated chronically with etretinate, 5 had detectable serum drug levels (in the range of 0.5 to 12 ng/mL) 2.1 to 2.9 years after therapy was discontinued. The long half-life appears to be due to storage of etretinate in adipose tissue.

OVERDOSAGE

In the event of acute overdosage, SORIATANE Capsules must be withdrawn at once. Symptoms of overdose are identical to acute hypervitaminosis A, ie, headache and vertigo. The acute oral toxicity (LD₅₀) of acitretin in both mice and rats was greater than 4000 mg/kg.

In one reported case of overdose, a 32-year-old male with Darier’s disease took 21 x 25 mg capsules (525 mg single dose). He vomited several hours later but experienced no other ill effects.

All female patients of childbearing potential who have taken an overdose of SORIATANE Capsules must:

1) Have a pregnancy test at the time of overdose; 2) Be counseled as per the boxed CONTRAINDICATIONS AND WARNINGS and PRECAUTIONS sections regarding birth defects and contraceptive use for at least 3 years’ duration after the overdose.

CONTRAINDICATIONS

Pregnancy Category X

(see boxed CONTRAINDICATIONS AND WARNINGS).

SORIATANE Capsules are contraindicated in patients with severely impaired liver or kidney function and in patients with chronic abnormally elevated blood lipid values (see boxed WARNINGS: Hepatotoxicity , WARNINGS: Lipids and Possible Cardiovascular Effects , and PRECAUTIONS).

An increased risk of hepatitis has been reported to result from combined use of methotrexate and etretinate. Consequently, the combination of methotrexate with SORIATANE Capsules is also contraindicated (see PRECAUTIONS: Drug Interactions ).

Since both SORIATANE Capsules and tetracyclines can cause increased intracranial pressure, their combined use is contraindicated (see WARNINGS: Pseudotumor Cerebri ).

SORIATANE Capsules are contraindicated in cases of hypersensitivity to the preparation (acitretin or excipients) or to other retinoids.