Hexalen

HEXALEN- altretamine capsule
MGI PHARMA, INC.

HEXUS PO5

Rx Only

MGI PHARMA

WARNINGS

  1. HEXALEN® capsules should only be given under the supervision of a physician experienced in the use of antineoplastic agents.
  2. Peripheral blood counts should be monitored at least monthly, prior to the initiation of each course of HEXALEN® capsules, and as clinically indicated (see Adverse Reactions).
  3. Because of the possibility of HEXALEN® capsules-related neurotoxicity, neurologic examination should be performed regularly during HEXALEN® capsules administration (see Adverse Reactions).

DESCRIPTION

HEXALEN® (altretamine) capsules, is a synthetic cytotoxic antineoplastic s-triazine derivative. HEXALEN® capsules contain 50 mg of altretamine for oral administration. Inert ingredients include lactose, anhydrous and calcium stearate. Altretamine, known chemically as N, N, N‘,N‘,N”,N”-hexamethyl-1,3,5-triazine-2,4,6-triamine, has the following structural formula:

Image from Drug Label Content

Its empirical formula is C9H18N6 with a molecular weight of 210.28. Altretamine is a white crystalline powder, melting at 172°± 1°C. Altretamine is practically insoluble in water but is increasingly soluble at pH 3 and below.

CLINICAL PHARMACOLOGY

The precise mechanism by which HEXALEN® capsules exerts its cytotoxic effect is unknown, although a number of theoretical possibilities have been studied. Structurally, HEXALEN® capsules resembles the alkylating agent triethylenemelamine, yet in vitro tests for alkylating activity of HEXALEN® capsules and its metabolites have been negative. HEXALEN® capsules has been demonstrated to be efficacious for certain ovarian tumors resistant to classical alkylating agents. Metabolism of altretamine is a requirement for cytotoxicity. Synthetic monohydroxymethylmelamines, and products of altretamine metabolism, in vitro and in vivo , can form covalent adducts with tissue macromolecules including DNA, but the relevance of these reactions to antitumor activity is unknown.

HEXALEN® capsules is well-absorbed following oral administration in humans, but undergoes rapid and extensive demethylation in the liver, producing variation in altretamine plasma levels. The principal metabolites are pentamethylmelamine and tetramethylmelamine.

Pharmacokinetic studies were performed in a limited number of patients and should be considered preliminary. After oral administration of HEXALEN® capsules to 11 patients with advanced ovarian cancer in doses of 120-300 mg/m2 , peak plasma levels (as measured by gas-chromatographic assay) were reached between 0.5 and 3 hours, varying from 0.2 to 20.8 mg/l. Half-life of the β-phase of elimination ranged from 4.7 to 10.2 hours. Altretamine and metabolites show binding to plasma proteins. The free fractions of altretamine, pentamethylmelamine and tetramethylmelamine are 6%, 25% and 50%, respectively.

Following oral administration of 14 C-ring-labeled altretamine (4 mg/kg), urinary recovery of radioactivity was 61% at 24 hours and 90% at 72 hours. Human urinary metabolites were Ndemethylated homologues of altretamine with <1% unmetabolized altretamine excreted at 24 hours.

After intraperitoneal administration of 14 C-ring-labeled altretamine to mice, tissue distribution was rapid in all organs, reaching a maximum at 30 minutes. The excretory organs (liver and kidney) and the small intestine showed high concentrations of radioactivity, whereas relatively low concentrations were found in other organs, including the brain.

There have been no formal pharmacokinetic studies in patients with compromised hepatic and/or renal function, though HEXALEN® capsules has been administered both concurrently and following nephrotoxic drugs such as cisplatin.

HEXALEN® capsules has been administered in 4 divided doses, with meals and at bedtime, though there is no pharmacokinetic data on this schedule nor information from formal interaction studies about the effect of food on its bioavailability or pharmacokinetics.

In two studies in patients with persistent or recurrent ovarian cancer following first-line treatment with cisplatin and/or alkylating agent-based combinations, HEXALEN® capsules was administered as a single agent for 14 or 21 days of a 28 day cycle. In the 51 patients with measurable or evaluable disease, there were 6 clinical complete responses, 1 pathologic complete response, and 2 partial responses for an overall response rate of 18%. The duration of these responses ranged from 2 months in a patient with a palpable pelvic mass to 36 months in a patient who achieved a pathologic complete response. In some patients, tumor regression was associated with improvement in symptoms and performance status.

INDICATIONS and USAGE

HEXALEN® (altretamine) capsules is indicated for use as a single agent in the palliative treatment of patients with persistent or recurrent ovarian cancer following first-line therapy with a cisplatin and/or alkylating agent-based combination.

CONTRAINDICATIONS

HEXALEN® capsules is contraindicated in patients who have shown hypersensitivity to it. HEXALEN® capsules should not be employed in patients with preexisting severe bone marrow depression or severe neurologic toxicity. HEXALEN® capsules has been administered safely, however, to patients heavily pretreated with cisplatin and/or alkylating agents, including patients with preexisting cisplatin neuropathies. Careful monitoring of neurologic function in these patients is essential.

WARNINGS

See boxed Warnings.

Concurrent administration of HEXALEN® capsules and antidepressants of the monoamine oxidase (MAO) inhibitor class may cause severe orthostatic hypotension. Four patients, all over 60 years of age, were reported to have experienced symptomatic hypotension after 4 to 7 days of concomitant therapy with HEXALEN® capsules and MAO inhibitors.

HEXALEN® capsules causes mild to moderate myelosuppression and neurotoxicity. Blood counts and a neurologic examination should be performed prior to the initiation of each course of therapy and the dose of HEXALEN® capsules adjusted as clinically indicated (see Dosage and Administration).

Pregnancy: Category D

HEXALEN® capsules has been shown to be embryotoxic and teratogenic in rats and rabbits when given at doses 2 and 10 times the human dose. HEXALEN® capsules may cause fetal damage when administered to a pregnant woman. If HEXALEN® capsules is used during pregnancy, or if the patient becomes pregnant while taking the drug, the patient should be apprised of the potential hazard to the fetus. Women of childbearing potential should be advised to avoid becoming pregnant.

PRECAUTIONS

General

Neurologic examination should be performed regularly (see Adverse Reactions).

Laboratory Tests

Peripheral blood counts should be monitored at least monthly, prior to the initiation of each course of HEXALEN® capsules, and as clinically indicated (see Adverse Reactions).

Drug Interactions

Concurrent administration of HEXALEN® capsules and antidepressants of the MAO inhibitor class may cause severe orthostatic hypotension (see Warnings section). Cimetidine, an inhibitor of microsomal drug metabolism, increased altretamine’s half-life and toxicity in a rat model.

Data from a randomized trial of HEXALEN® capsules and cisplatin plus or minus pyridoxine in ovarian cancer indicated that pyridoxine significantly reduced neurotoxicity; however, it adversely affected response duration suggesting that pyridoxine should not be administered with HEXALEN® capsules and/or cisplatin (1).

Carcinogenesis, Mutagenesis and Impairment of Fertility

The carcinogenic potential of HEXALEN® capsules has not been studied in animals, but drugs with similar mechanisms of action have been shown to be carcinogenic. HEXALEN® capsules was weakly mutagenic when tested in strain TA100 of Salmonella typhimurium. HEXALEN® capsules administered to female rats 14 days prior to breeding through the gestation period had no adverse effect on fertility, but decreased post-natal survival at 120 mg/m2 /day and was embryocidal at 240 mg/m2 /day. Administration of 120 mg/m2 /day HEXALEN® capsules to male rats for 60 days prior to mating resulted in testicular atrophy, reduced fertility and a possible dominant lethal mutagenic effect. Male rats treated with HEXALEN® capsules at 450 mg/m2 /day for 10 days had decreased spermatogenesis, atrophy of testes, seminal vesicles and ventral prostate.

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