ACITRETIN Drug Interactions: What You Need to Know

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 2-way crossover trial, 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 per kg body weight). A mean peak etretinate concentration of 59 ng per mL (range: 22 to 105 ng per mL) was observed, and extrapolation of AUC values indicated that the formation of etretinate in this trial 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 subjects on acitretin therapy in several foreign trials (10 to 80 mg per day), 16% had measurable etretinate levels (>5 ng per mL). Etretinate has a much longer elimination half-life compared with that of acitretin. In one trial the apparent mean terminal half-life after 6 months of therapy was approximately 120 days (range: 84 to 168 days). In another trial of 47 subjects treated chronically with etretinate, 5 had detectable serum drug levels (in the range of 0.5 to 12 ng per 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. Progestin-only Contraceptives: It has not been established if there is a pharmacokinetic interaction between acitretin and combined oral contraceptives. However, it has been established that acitretin interferes with the contraceptive effect of microdosed progestin preparations. 1 Microdosed “minipill” progestin preparations are not recommended for use with acitretin. It is not known whether other progestin-only contraceptives, such as implants and injectables, are adequate methods of contraception during acitretin therapy.

Drug

Interactions: Ethanol: Clinical evidence has shown that etretinate can be formed with concurrent ingestion of acitretin and ethanol (see boxed CONTRAINDICATIONS AND WARNINGS and CLINICAL PHARMACOLOGY: Pharmacokinetics ). Glyburide: In a trial of 7 healthy male volunteers, acitretin treatment potentiated the blood glucose-lowering effect of glyburide (a sulfonylurea similar to chlorpropamide) in 3 of the 7 subjects. Repeating the trial with 6 healthy male volunteers in the absence of glyburide did not detect an effect of acitretin on glucose tolerance. Careful supervision of diabetic patients under treatment with acitretin is recommended (see CLINICAL PHARMACOLOGY : Pharmacokinetics and DOSAGE AND ADMINISTRATION ).

Hormonal

Contraceptives: It has not been established if there is a pharmacokinetic interaction between acitretin and combined oral contraceptives. However, it has been established that acitretin interferes with the contraceptive effect of microdosed progestin “minipill” preparations. Microdosed “minipill” progestin preparations are not recommended for use with acitretin (see CLINICAL PHARMACOLOGY : Pharmacokinetic Drug Interactions ). It is not known whether other progestin-only contraceptives, such as implants and injectables, are adequate methods of contraception during acitretin therapy . Methotrexate: An increased risk of hepatitis has been reported to result from combined use of methotrexate and etretinate. Consequently, the combination of methotrexate with acitretin is also contraindicated (see CONTRAINDICATIONS ). Phenytoin: If acitretin is given concurrently with phenytoin, the protein binding of phenytoin may be reduced. Tetracyclines: Since both acitretin and tetracyclines can cause increased intracranial pressure, their combined use is contraindicated (see CONTRAINDICATIONS and WARNINGS: Pseudotumor Cerebri ). Vitamin A and Oral Retinoids: Concomitant administration of vitamin A and/or other oral retinoids with acitretin must be avoided because of the risk of hypervitaminosis A. Other: There appears to be no pharmacokinetic interaction between acitretin and cimetidine, digoxin, or glyburide. Investigations into the effect of acitretin on the protein binding of anticoagulants of the coumarin type (warfarin) revealed no interaction.

CONTRAINDICATIONS Pregnancy See boxed CONTRAINDICATIONS AND WARNINGS . Acitretin 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 acitretin capsules is also contraindicated (see PRECAUTIONS: Drug Interactions ). Since both acitretin capsules and tetracyclines can cause increased intracranial pressure, their combined use is contraindicated (see WARNINGS: Pseudotumor Cerebri ). Acitretin capsules are contraindicated in cases of hypersensitivity (e.g., angioedema, urticaria) to the preparation (acitretin or excipients) or to other retinoids .

WARNINGS (See also boxed CONTRAINDICATIONS AND WARNINGS .) Hepatotoxicity: Of the 525 subjects treated in U.S. clinical trials, 2 had clinical jaundice with elevated serum bilirubin and transaminases considered related to treatment with acitretin capsules. Liver function test results in these subjects returned to normal after acitretin capsules were discontinued. Two of the 1,289 subjects treated in European clinical trials developed biopsy-confirmed toxic hepatitis. A second biopsy in one of these subjects revealed nodule formation suggestive of cirrhosis. One subject in a Canadian clinical trial of 63 subjects developed a 3-fold increase of transaminases. A liver biopsy of this subject showed mild lobular disarray, multifocal hepatocyte loss, and mild triaditis of the portal tracts compatible with acute reversible hepatic injury. The subject’s transaminase levels returned to normal 2 months after acitretin capsules were discontinued. The potential of therapy with acitretin capsules to induce hepatotoxicity was prospectively evaluated using liver biopsies in an open-label trial of 128 subjects. Pretreatment and posttreatment biopsies were available for 87 subjects. A comparison of liver biopsy findings before and after therapy revealed 49 (58%) subjects showed no change, 21 (25%) improved, and 14 (17%) subjects had a worsening of their liver biopsy status.

For

6 subjects, the classification changed from class 0 (no pathology) to class I (normal fatty infiltration; nuclear variability and portal inflammation; both mild); for 7 subjects, the change was from class I to class II (fatty infiltration, nuclear variability, portal inflammation, and focal necrosis; all moderate to severe); and for 1 subject, the change was from class II to class IIIb (fibrosis, moderate to severe). No correlation could be found between liver function test result abnormalities and the change in liver biopsy status, and no cumulative dose relationship was found. Elevations of AST (SGOT), ALT (SGPT), GGT (GGTP), or LDH have occurred in approximately 1 in 3 subjects treated with acitretin capsules. Of the 525 subjects treated in clinical trials in the U.S., treatment was discontinued in 20 (3.8%) due to elevated liver function test results. If hepatotoxicity is suspected during treatment with acitretin capsules, the drug should be discontinued and the etiology further investigated. Ten of 652 subjects treated in U.S. clinical trials of etretinate, of which acitretin is the active metabolite, had clinical or histologic hepatitis considered to be possibly or probably related to etretinate treatment. There have been reports of hepatitis-related deaths worldwide; a few of these subjects had received etretinate for a month or less before presenting with hepatic symptoms or signs.

Skeletal

Abnormalities In adults receiving long-term treatment with acitretin capsules, appropriate examinations should be periodically performed in view of possible ossification abnormalities (see ADVERSE REACTIONS ). Because the frequency and severity of iatrogenic bony abnormality in adults is low, periodic radiography is only warranted in the presence of symptoms or long-term use of acitretin capsules. If such disorders arise, the continuation of therapy should be discussed with the patient on the basis of a careful risk/benefit analysis. In clinical trials with acitretin capsules, subjects were prospectively evaluated for evidence of development or change in bony abnormalities of the vertebral column, knees, and ankles.

Of

380 subjects treated with acitretin capsules, 15% had preexisting abnormalities of the spine which showed new changes or progression of preexisting findings. Changes included degenerative spurs, anterior bridging of spinal vertebrae, diffuse idiopathic skeletal hyperostosis, ligament calcification, and narrowing and destruction of a cervical disc space. De novo changes (formation of small spurs) were seen in 3 subjects after 1½ to 2½ years. Six of 128 subjects treated with acitretin capsules showed abnormalities in the knees and ankles before treatment that progressed during treatment.

In

5, these changes involved the formation of additional spurs or enlargement of existing spurs. The sixth subject had degenerative joint disease which worsened. No subjects developed spurs de novo . Clinical complaints did not predict radiographic changes. Lipids and Possible Cardiovascular Effects Blood lipid determinations should be performed before acitretin capsules are administered and again at intervals of 1 to 2 weeks until the lipid response to the drug is established, usually within 4 to 8 weeks. In subjects receiving acitretin capsules during clinical trials, 66% and 33% experienced elevation in triglycerides and cholesterol, respectively. Decreased high density lipoproteins (HDL) occurred in 40% of subjects. These effects of acitretin capsules were generally reversible upon cessation of therapy. Subjects with an increased tendency to develop hypertriglyceridemia included those with disturbances of lipid metabolism, diabetes mellitus, obesity, increased alcohol intake, or a familial history of these conditions. Because of the risk of hypertriglyceridemia, serum lipids must be more closely monitored in high-risk patients and during long-term treatment. Hypertriglyceridemia and lowered HDL may increase a patient’s cardiovascular risk status. Although no causal relationship has been established, there have been postmarketing reports of acute myocardial infarction or thromboembolic events in patients on therapy with acitretin capsules. In addition, elevation of serum triglycerides to greater than 800 mg per dL has been associated with fatal fulminant pancreatitis. Therefore, dietary modifications, reduction in dose of acitretin capsules, or drug therapy should be employed to control significant elevations of triglycerides. If, despite these measures, hypertriglyceridemia and low HDL levels persist, the discontinuation of acitretin capsules should be considered.

Ophthalmologic Effects

The eyes and vision of 329 subjects treated with acitretin capsules were examined by ophthalmologists. The findings included dry eyes (23%), irritation of eyes (9%), and brow and lash loss (5%). The following were reported in less than 5% of subjects: Bell’s palsy, blepharitis and/or crusting of lids, blurred vision, conjunctivitis, corneal epithelial abnormality, cortical cataract, decreased night vision, diplopia, itchy eyes or eyelids, nuclear cataract, pannus, papilledema, photophobia, posterior subcapsular cataract, recurrent sties, and subepithelial corneal lesions. Any patient treated with acitretin capsules who is experiencing visual difficulties should discontinue the drug and undergo ophthalmologic evaluation.

Pancreatitis

Lipid elevations occur in 25% to 50% of subjects treated with acitretin capsules. Triglyceride increases sufficient to be associated with pancreatitis are much less common, although fatal fulminant pancreatitis has been reported. There have been rare reports of pancreatitis during therapy with acitretin capsules in the absence of hypertriglyceridemia.

Pseudotumor Cerebri

Acitretin capsules and other retinoids administered orally have been associated with cases of pseudotumor cerebri (benign intracranial hypertension). Some of these events involved concomitant use of isotretinoin and tetracyclines. However, the event seen in a single patient receiving acitretin capsules was not associated with tetracycline use. Early signs and symptoms include papilledema, headache, nausea and vomiting, and visual disturbances. Patients with these signs and symptoms should be examined for papilledema and, if present, should discontinue acitretin capsules immediately and be referred for neurological evaluation and care. Since both acitretin capsules and tetracyclines can cause increased intracranial pressure, their combined use is contraindicated (see CONTRAINDICATIONS ).

Capillary Leak Syndrome

Capillary leak syndrome, a potential manifestation of retinoic acid syndrome, has been reported in patients receiving acitretin capsules. Features of this syndrome may include localized or generalized edema with secondary weight gain, fever, and hypotension. Rhabdomyolysis and myalgias have been reported in association with capillary leak syndrome, and laboratory tests may reveal neutrophilia, hypoalbuminemia, and an elevated hematocrit. Discontinue acitretin capsules if capillary leak syndrome develops during therapy.

Exfoliative Dermatitis/Erythroderma

Exfoliative dermatitis/erythroderma has been reported in patients receiving acitretin capsules. Discontinue acitretin capsules if exfoliative dermatitis/erythroderma occurs during therapy.