Mechanism of Action

Prostate cancer is known to be androgen sensitive and responds to androgen ablation. In animal studies, nilutamide has demonstrated antiandrogenic activity without other hormonal (estrogen, progesterone, mineralocorticoid, and glucocorticoid) effects. In vitro, nilutamide blocks the effects of testosterone at the androgen receptor level. In vivo, nilutamide interacts with the androgen receptor and prevents the normal androgenic response.

Pharmacokinetics

Clinical Studies

Nilutamide through its antiandrogenic activity can complement surgical castration, which suppresses only testicular androgens. The effects of the combined therapy were studied in patients with previously untreated metastatic prostate cancer.

In a double-blind, randomized, multicenter study that enrolled 457 patients (225 treated with orchiectomy and NILANDRON, 232 treated with orchiectomy and placebo), the NILANDRON group showed a statistically significant benefit in time to progression and time to death. The results are summarized below.

Metastatic Prostate Cancer

NILANDRON tablets are indicated for use in combination with surgical castration for the treatment of metastatic prostate cancer (Stage D2).

For maximum benefit, NILANDRON treatment must begin on the same day as or on the day after surgical castration.

Hepatitis

Rare cases of death or hospitalization due to severe liver injury have been reported post-marketing in association with the use of NILANDRON. Hepatotoxicity in these reports generally occurred within the first 3 to 4 months of treatment. Hepatitis or marked increases in liver enzymes leading to drug discontinuation occurred in 1% of NILANDRON patients in controlled clinical trials.

Serum transaminase levels should be measured prior to starting treatment with NILANDRON, at regular intervals for the first 4 months of treatment, and periodically thereafter. Liver function tests should also be obtained at the first sign or symptom suggestive of liver dysfunction, e.g. nausea, vomiting, abdominal pain, fatigue, anorexia, "flu-like" symptoms, dark urine, jaundice or right upper quadrant tenderness. If at any time, a patient has jaundice or their ALT rises above 2 times the upper limit of normal, NILANDRON should be immediately discontinued with close followup of liver function tests until resolution.

Use in Women

NILANDRON has no indication for women, and should not be used in this population, particularly for non-serious or non-life threatening conditions.

Other

Foreign postmarketing surveillance has revealed isolated cases of aplastic anemia in which a causal relationship with NILANDRON could not be ascertained.

General

Information for Patients

Patients should be informed that NILANDRON tablets should be started on the day of or on the day after, surgical castration. They should also be informed that they should not interrupt their dosing of NILANDRON or stop taking this medication without consulting their physician.

Because of the possibility of interstitial pneumonitis, patients should also be told to report immediately any dyspnea or aggravation of pre-existing dyspnea.

Because of the possibility of hepatitis, patients should be told to consult with their physician should nausea, vomiting, abdominal pain or jaundice occur.

Because of the possibility of an intolerance to alcohol (facial flushes, malaise, hypotension) following ingestion of NILANDRON, it is recommended that intake of alcoholic beverages be avoided by patients who experience this reaction. This effect has been reported in about 5% of patients treated with NILANDRON.

In clinical trials, 13% to 57% of patients receiving NILANDRON reported a delay in adaptation to dark, ranging from seconds to a few minutes, when passing from a lighted area to a dark area. This effect sometimes does not abate as drug treatment is continued. Patients who experience this effect should be cautioned about driving at night or through tunnels. This effect can be alleviated by the wearing of tinted glasses.

Drug Interactions

In vitro, nilutamide has been shown to inhibit the activity of liver cytochrome P-450 isoenzymes and, therefore, may reduce the metabolism of compounds requiring these systems.

Consequently, drugs with a low therapeutic margin, such as vitamin K antagonists, phenytoin, and theophylline, could have a delayed elimination and increases in their serum half-life leading to a toxic level. The dosage of these drugs or others with a similar metabolism may need to be modified if they are administered concomitantly with nilutamide. For example, when vitamin K antagonists are administered concomitantly with nilutamide, prothrombin time should be carefully monitored and, if necessary, the dosage of vitamin K antagonists should be reduced.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Administration of nilutamide to rats for 18 months at doses of 0, 5, 15, or 45 mg/kg/day produced benign Leydig cell tumors in 35% of the high-dose male rats (AUC exposures in high-dose rats were approximately 1–2 times human AUC exposures with therapeutic doses). The increased incidence of Leydig cell tumors is secondary to elevated luteinizing hormone (LH) concentrations resulting from loss of feedback inhibition at the pituitary. Elevated LH and testosterone concentrations are not observed in castrated men receiving NILANDRON. Nilutamide had no effect on the incidence, size or time of onset of any spontaneous tumor in rats.

Nilutamide displayed no mutagenic effects in a variety of in vitro and in vivo tests (Ames test, mouse micronucleus test, and two chromosomal aberration tests).

In reproduction studies in rats, nilutamide had no effect on the reproductive function of males and females, and no lethal, teratogenic or growth-suppressive effects on fetuses were found. The maximal dose at which nilutamide did not affect reproductive function in either sex or have an effect on fetuses was estimated to be 45 mg/kg orally (AUC exposures in rats approximately 1–2 times human therapeutic AUC exposures).

Pregnancy

Animal reproduction studies have not been conducted with nilutamide. It is also not known whether nilutamide can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. Nilutamide should be given to a pregnant woman only if clearly needed.

Pediatric Use

Safety and effectiveness in pediatric patients have not been determined.

Animal Pharmacology and Toxicology

Administration of NILANDRON to beagle dogs resulted in drug-related deaths at dose levels that produce AUC exposures in dogs much lower than the AUC exposures of men receiving the therapeutic doses of 150 and 300 mg/day. Nilutamide-induced toxicity in dogs was cumulative with progressively lower doses producing death when given for longer durations. Nilutamide given to dogs at 60 mg/kg/day (1–2 times human AUC exposure) for 1 month produced 100% mortality. Administration of 20 and 30 mg/kg/day nilutamide (1/2–1 times human AUC exposure) for 6 months resulted in 20% and 70% mortality in treated dogs. Administration to dogs of 3, 6, and 12 mg/kg/day nilutamide (1/10–1/2 human AUC exposure) for 1 year resulted in 8%, 33%, and 50% mortality, respectively. A "no-effect level" for nilutamide-induced mortality in dogs was not identified. Pathology data from the one-year oral toxicity study suggest that the deaths in dogs were secondary to liver toxicity. Marked-to-massive hepatocellular swelling and vacuolization were observed in affected dogs. Liver toxicity in dogs was not consistently associated with elevations of liver enzymes.

Administration of nilutamide to rats at a dose level of 45 mg/kg/day (AUC exposure in rats 1–2 times human therapeutic AUC exposures) for 18 months increased the incidence of lung pathology (granulomatous inflammation and chronic alveolitis).

The hepatic and pulmonary adverse effects observed in nilutamide-treated animals and men are similar to effects observed with another nitroaromatic compound, nitrofurantoin. Nilutamide and nitrofurantoin are both metabolized in vitro to nitroanion free-radicals by microsomal NADPH-cytochrome P450 reductase in the lungs and liver of rats and humans.