2.1 Testing Prior to Megestrol Acetate Administration

• Obtain a negative pregnancy test in females of reproductive potential prior to initiating treatment with megestrol acetate [see Contraindications (4), Warnings and Precautions (5.2), Use in Specific Populations (8.1, 8.3)].

2.2 Dosage and Administration

• The recommended adult initial dosage of megestrol acetate oral suspension (125 mg/mL) is 625 mg/day (5 mL/day or one teaspoon daily).
• Shake the container well before using.
• This strength (125 mg/mL) is not substitutable with other strengths (e.g., 40 mg/mL). Refer to the prescribing information of the 40 mg/mL product for dosage recommendations for the 40 mg/mL strength.

5.1 General

• Effects on HIV viral replication have not been determined.
• Use with caution in patients with a history of thromboembolic disease.

5.2 Fetal Toxicity

Based on animal studies, megestrol acetate may cause fetal harm when administered to a pregnant woman. Pregnant rats treated with low doses of megestrol acetate resulted in a reduction in fetal weight and number of live births, and feminization of male fetuses. There are no available human data to assess for any drug associated risks of miscarriage, birth defects, or adverse maternal or fetal outcomes. If this drug is used during pregnancy, or if the patient becomes pregnant while taking (receiving) this drug, advise the patient  of the potential hazard to the fetus [see Use in Specific Populations (8.1), Nonclinical Toxicology (13.1)].

Obtain a pregnancy test in females of reproductive potential prior to initiating treatment with megestrol acetate oral suspension [see Dosage and Administration (2.1)]. Advise females of reproductive potential to use effective contraception while taking megestrol acetate oral suspension  [see Use in Specific Populations (8.3)].

5.3 Adrenal Insufficiency

The glucocorticoid activity of megestrol acetate oral suspension has not been fully evaluated. Clinical cases of overt Cushing’s Syndrome have been reported in association with the chronic use of megestrol acetate. In addition, clinical cases of adrenal insufficiency have been observed in patients receiving or being withdrawn from chronic megestrol acetate therapy in the stressed and non-stressed state. Furthermore, adrenocorticotropin (ACTH) stimulation testing has revealed the frequent occurrence of asymptomatic pituitary-adrenal suppression in patients treated with chronic megestrol acetate therapy. Therefore, the possibility of adrenal insufficiency should be considered in any patient receiving or being withdrawn from chronic megestrol acetate oral suspension therapy who presents with symptoms and/or signs suggestive of hypoadrenalism (e.g., hypotension, nausea, vomiting, dizziness, or weakness) in either the stressed or non-stressed state. Laboratory evaluation for adrenal insufficiency and consideration of replacement or stress doses of a rapidly acting glucocorticoid are strongly recommended in such patients. Failure to recognize inhibition of the hypothalamic-pituitary adrenal axis may result in death. Finally, in patients who are receiving or being withdrawn from chronic megestrol acetate oral suspension therapy, consideration should be given to the use of empiric therapy with stress doses of a rapidly acting glucocorticoid during stress or serious intercurrent illness (e.g., surgery, infection).

5.4 Diabetes

Clinical cases of new onset diabetes mellitus and exacerbation of pre-existing diabetes mellitus have been reported in association with the chronic use of megestrol acetate.

6.1 Serious and Otherwise Important Adverse Reactions

The following serious reactions and otherwise important adverse drug reactions are discussed in greater detail in other sections of the labeling:

• Hypersensitivity[see Contraindications (4)]
• Thromboembolic Disease [see Warnings and Precautions (5.1)]
• Adrenal Insufficiency [see Warnings and Precautions (5.3)]
• Diabetes [see Warnings and Precautions (5.4)]

6.2 Clinical Trial Experience

Because clinical trials are conducted under widely varying conditions, adverse reactions observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety of megestrol acetate oral suspension (125 mg/mL) was based on three studies of megestrol acetate oral suspension (40 mg/mL). The adverse reaction profile of these 3 studies are presented below.

Adverse events which occurred in at least 5% of patients in any arm of the two clinical efficacy trials and the open trial for megestrol acetate oral suspension are listed below by treatment group. All patients listed had at least one post baseline visit during the 12 study weeks.

Table 1: Adverse Events

Adverse events which occurred in 1% to 3% of all patients enrolled in the two clinical efficacy trials with at least one follow-up visit during the first 12 weeks of the study are listed below by body system. Adverse events occurring less than 1% are not included. There were no significant differences between incidence of these events in patients treated with megestrol acetate and patients treated with placebo.

Body as a Whole - abdominal pain, chest pain, infection, moniliasis and sarcoma

Cardiovascular System - cardiomyopathy and palpitation

Digestive System - constipation, dry mouth, hepatomegaly, increased salivation and oral moniliasis

Hemic and Lymphatic System - leukopenia

Metabolic and Nutritional - LDH increased, edema and peripheral edema

Nervous System - paresthesia, confusion, convulsion, depression, neuropathy, hypesthesia and abnormal thinking

Respiratory System - dyspnea, cough, pharyngitis and lung disorder

Skin and Appendages - alopecia, herpes, pruritus, vesiculobullous rash, sweating and skin disorder

Special Senses - amblyopia

Urogenital System - albuminuria, urinary incontinence, urinary tract infection and gynecomastia.

6.3 Postmarketing Experience

Postmarketing reports associated with megestrol acetate oral suspension include thromboembolic phenomena including thrombophlebitis, deep vein thrombosis, and pulmonary embolism; and glucose intolerance.

7.1 Indinavir

Due to the significant decrease in the exposure of indinavir by megestrol acetate, administration of a higher dose of indinavir should be considered when coadministering with megestrol acetate [See Clinical Pharmacology (12.3)].

7.2 Zidovudine and Rifabutin

No dosage adjustment for zidovudine and rifabutin is needed when megestrol acetate is coadministered with these drugs [See Clinical Pharmacology (12.3)].

8.1 Pregnancy

Risk Summary

Based on animal data, megestrol acetate may cause fetal harm when administered to a pregnant woman and is contraindicated during pregnancy [see Contraindications (4)]. There are no available human data to assess for any drug-associated risks of miscarriage, birth defects, or adverse maternal or fetal outcomes. There are no adequate animal developmental toxicity data at clinically relevant doses. Pregnant rats treated with low doses of megestrol acetate resulted in a reduction in fetal weight and number of live births, and feminization of male fetuses at doses below maximum recommended clinical dosing based on body surface area (see Data). Advise pregnant women of the potential risk to the fetus.

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and of miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.

Data

Reproduction studies were performed in pregnant rats at oral doses ranging from 0.05 to 12.5 mg/kg/day, which are below the maximum recommended clinical dose based on body surface area. Reduction in fetal weight and number of live births were observed at 12.5 mg/kg/day (5 times lower than the maximum clinical dose) when dams were dosed on days 12 through 18 of pregnancy. Feminization of male fetuses also occurred when dams were dosed on days 13 through 20 of pregnancy at 3 mg/kg/day, approximately 22 times below the maximum clinical dose.

8.2 Lactation

Risk Summary

The Centers for Disease Control and Prevention recommend that HIV-1 infected mothers not breastfeed their infants to avoid risking postnatal transmission of HIV-1. Megestrol acetate is present in human milk. There are no data on the effects of megesterol acetate on the breastfed infant or the effects on milk production. Because of the potential for HIV transmission and adverse effects on a breastfed infant, instruct mothers not to breastfeed if they are taking megestrol acetate oral suspension.

8.3 Females and Males of Reproductive Potential

Pregnancy testing

Pregnancy testing is recommended prior to treatment with megestrol acetate oral suspension [see Dosage and Administration (2.1), Use in Specific Populations (8.1)].

Contraception

Megestrol acetate oral suspension may cause fetal harm when administered during pregnancy [see Use in Specific Populations (8.1)]. Advise females of reproductive potential to use effective contraception during treatment with megestrol acetate oral suspension.

8.4 Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

8.5 Geriatric Use

Clinical studies of megestrol acetate oral suspension in the treatment of anorexia, cachexia, or an unexplained significant weight loss in patients with AIDS did not include sufficient numbers of patients aged 65 years and older to determine whether they respond differently than younger patients. Other reported clinical experience has not identified differences in responses between elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Megestrol acetate is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

8.6 Use in Women

Megestrol acetate has had limited use in HIV infected women.

All 10 women in the clinical trials reported breakthrough bleeding. Megestrol acetate is a progesterone derivative, which may induce vaginal bleeding in women.

12.1 Mechanism of Action

Several investigators have reported on the appetite enhancing property of megestrol acetate and its possible use in cachexia. The precise mechanism by which megestrol acetate produces effects in anorexia and cachexia is unknown at the present time.

12.3 Pharmacokinetics

Absorption and Distribution

Mean plasma concentrations of megestrol acetate after administration of 625 mg (125 mg/mL) of megestrol acetate oral suspension are equivalent under fed conditions to 800 mg (40 mg/mL) of megestrol acetate oral suspension in healthy volunteers.

In order to characterize the dose proportionality of megestrol acetate oral suspension (125 mg/mL), pharmacokinetic studies across a range of doses were conducted when administered under fasting and fed conditions. Pharmacokinetics of megestrol acetate was linear in the dosing range between 150 mg and 675 mg after megestrol acetate oral suspension (125 mg/mL) administration regardless of meal condition. The mean peak plasma concentration (Cmax) and the mean area under the concentration time-curve (AUC) after a high fat meal were increased by 48% and 36%, respectively, compared to those under the fasting condition after 625 mg of megestrol acetate oral suspension (125 mg/mL) administration. This food effect is less than that seen for the original formulation, megestrol acetate 800 mg/20 mL, where a high fat meal significantly increased AUC and Cmax of megestrol acetate to 2-fold and 7-fold, respectively, compared to those under the fasting condition. There was no difference in safety following administration in the fed state, therefore megestrol acetate oral suspension (125 mg/mL) could be taken without regard to meals.

Plasma steady state pharmacokinetics of megestrol acetate was evaluated in 10 adult, cachectic male adult patients with acquired immunodeficiency syndrome (AIDS) and an involuntary weight loss greater than 10% of baseline who received single oral doses of 800 mg/day of megestrol acetate oral suspension for 21 days. The Mean (±1SD) Cmax of megestrol acetate was 753 (±539) ng/mL. The mean AUC was 10476 (±7788) ng x hr/mL. Median Tmax value was five hours.

In another study, 24 asymptomatic HIV seropositive male adult subjects were dosed once daily with 750 mg of megestrol acetate oral suspension for 14 days. Mean Cmax and AUC values were 490 (±238) ng/mL and 6779 (±3048) hr x ng/mL, respectively. The median Tmax value was three hours. The mean Cmin value was 202 (±101) ng/mL. The mean % of fluctuation value was 107 (±40).

Metabolism and Excretion

The major route of drug elimination in humans is urine. When radio-labeled megestrol acetate was administered to humans in doses of 4 to 90 mg, the urinary excretion within 10 days ranged from 56.5% to 78.4% (mean 66.4%) and fecal excretion ranged from 7.7% to 30.3% (mean 19.8%). The total recovered radioactivity varied between 83.1% and 94.7% (mean 86.2%).

Megestrol acetate metabolites which were identified in urine constituted 5% to 8% of the dose administered. Respiratory excretion as labeled carbon dioxide and fat storage may have accounted for at least part of the radioactivity not found in urine and feces.

The mean elimination half-life of megestrol ranged from 20 to 50 hours in healthy subjects.

Specific Populations

The pharmacokinetics of megestrol acetate has not been studied in specific population, for example, pediatric, renal impairment, and hepatic impairment.

Drug Interactions

The effects of indinavir, zidovudine or rifabutin on the pharmacokinetics of megestrol acetate were not studied.

Zidovudine

Pharmacokinetic studies show that there are no significant alterations in exposure of zidovudine when megestrol acetate is administered with this drug.

Rifabutin

Pharmacokinetic studies show that there are no significant alterations in exposure of rifabutin when megestrol acetate is administered with this drug.

Indinavir

A pharmacokinetic study in healthy male subjects demonstrated that coadministration of megestrol acetate (675 mg for 14 days) and indinavir (single dose 800 mg) results in a significant decrease in the pharmacokinetic parameters (~32% for Cmax and ~21% for AUC) of indinavir.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Data on carcinogenesis were obtained from studies conducted in dogs, monkeys and rats treated with megestrol acetate at doses below the recommended clinical dose based on body surface area. No males were used in the dog and monkey studies. In female beagles, megestrol acetate (0.01, 0.1 or 0.25 mg/kg/day) administered for up to 7 years induced both benign and malignant tumors of the breast at doses greater than or equal to 0.01 mg/kg/day, approximately 75 to 187 times below the maximum clinical dose. In female monkeys, no tumors were found following 10 years of treatment with 0.01, 0.1 or 0.5 mg/kg/day megestrol acetate, up to 65 times below the maximum clinical dose. Pituitary tumors were observed in female rats treated for 2 years with 3.9 or 10 mg/kg/day of megestrol acetate, approximately 6 to 17 times below the maximum clinical dose. The relationship of these tumors in rats and dogs to humans is unknown but should be considered in assessing the risk-to-benefit ratio when prescribing megestrol acetate oral suspension (125 mg/mL) and in surveillance of patients on therapy.

Megestrol acetate induced unscheduled DNA synthesis in primary cultures of human hepatocytes, but not in rat hepatocytes. Megestrol administered to mice increased the frequency of sister chromatid exchange and chromosomal aberrations in bone marrow cells after single intraperitonial doses of 16.25 and 32.50 mg/kg.

Impaired reproductive capability was observed in male offspring born to female rats treated during gestation days 13 through 20 with oral doses greater than or equal to 3 mg/kg/day megestrol, approximately 22 times below the maximum clinical dose. Female dogs treated daily with megestrol oral capsules for 7 years experienced a complete cessation of estrus activity and ovulation at doses of 0.1, or 0.25 mg/kg/day, approximately 187 and 75 times below the maximum clinical dose, respectively.

13.2 Animal Toxicology and/or Pharmacology

Long-term treatment with megestrol acetate oral suspension (125 mg/mL) may increase the risk of respiratory infections. A trend toward increased frequency of respiratory infections, decreased lymphocyte counts and increased neutrophil counts was observed in a two-year chronic toxicity/carcinogenicity study of megestrol acetate conducted in rats.