"Just one dose of zoledronic acid given at the start of antiretroviral therapy (ART) may prevent ART-associated bone loss during the first 48 weeks of therapy, according to a study published online May 18 in Clinical Infectious Diseases."...
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.
Absorption And Distribution
Mean plasma concentrations of megestrol acetate after administration of 625 mg (125 mg/mL) of Megace® ES 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 Megace® ES, 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 Megace® ES 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 Megace® ES 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 Megace® ES 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 Cmjn 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.
The pharmacokinetics of megestrol acetate has not been studied in specific population, for example, pediatric, renal impairment, and hepatic impairment.
The effects of indinavir, zidovudine or rifabutin on the pharmacokinetics of megestrol acetate were not studied.
Pharmacokinetic studies show that there are no significant alterations in exposure of zidovudine when megestrol acetate is administered with this drug.
Pharmacokinetic studies show that there are no significant alterations in exposure of rifabutin when megestrol acetate is administered with this drug.
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.
Animal Pharmacology And/Or Toxicology
Long-term treatment with Megace® ES 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.
The efficacy of Megace® ES (megestrol acetate oral suspension, 125 mg/mL) was based on two trials of megestrol acetate oral suspension (40 mg/mL). These two trials are described below.
One was a multicenter, randomized, double-blind, placebo-controlled study comparing megestrol acetate (MA) at doses of 100 mg, 400 mg, and 800 mg per day versus placebo in AIDS patients with anorexia/cachexia and significant weight loss. Of the 270 patients entered on study, 195 met all inclusion/exclusion criteria, had at least two additional post baseline weight measurements over a 12 week period or had one post baseline weight measurement but dropped out for therapeutic failure. The percent of patients gaining 2.3 kg or more at maximum weight gain in 12 study weeks was statistically significantly greater for the 800 mg (64%) and 400 mg (57%) MAtreated groups than for the placebo group (24%). Mean weight increased from baseline to last evaluation in 12 study weeks in the 800 mg MA-treated group by 3.5 kg, the 400 mg MA group by 1.9 kg, the 100 mg MA group by 0.9 kg and decreased in the placebo group by 0.7 kg. Mean weight changes at 4, 8 and 12 weeks for patients evaluable for efficacy in the two clinical trials is shown graphically. Changes in body composition during the 12 study weeks as measured by bioelectrical impedance analysis showed increases in non-water body weight in the MA-treated groups. In addition, edema developed or worsened in only 3 patients.
Greater percentages of MA-treated patients in the 800 mg group (89%), the 400 mg group (68%) and the 100 mg group (72%), than in the placebo group (50%), showed an improvement in appetite at last evaluation during the 12 study weeks. A statistically significant difference was observed between the 800 mg MA-treated group and the placebo group in the change in caloric intake from baseline to time of maximum weight change. Patients were asked to assess weight change, appetite, appearance, and overall perception of well-being in a 9 question survey. At maximum weight change only the 800 mg MA-treated group gave responses that w ere statistically significantly more favorable to all questions when compared to the placebo-treated group. A dose response was noted in the survey with positive responses correlating with higher dose for all questions.
The second trial was a multicenter, randomized, double-blind, placebo-controlled study comparing megestrol acetate 800 mg/day versus placebo in AIDS patients with anorexia/cachexia and significant weight loss. Of the 100 patients entered on study, 65 met all inclusion/exclusion criteria, had at least two additional post baseline weight measurements over a 12 week period or had one post baseline weight measurement but dropped out for therapeutic failure. Patients in the 800 mg MA-treated group had a statistically significantly larger increase in mean maximum weight change than patients in the placebo group. From baseline to study week 12, mean weight increased by 5.1 kg in the MA-treated group and decreased 1.0 kg in the placebo group. Changes in body composition as measured by bioelectrical impedance analysis showed increases in nonwater weight in the MA-treated group (see Clinical Studies table). No edema was reported in the MA-treated group. A greater percentage of MA-treated patients (67%) than placebo-treated patients (38%) showed an improvement in appetite at last evaluation during the 12 study weeks; this difference was statistically significant. There were no statistically significant differences between treatment groups in mean caloric change or in daily caloric intake at time to maximum weight change. In the same 9 question survey referenced in the first trial, patients' assessments of weight change, appetite, appearance, and overall perception of well-being showed increases in mean scores in MA-treated patients as compared to the placebo group.
In both trials, patients tolerated the drug well and no statistically significant differences were seen between the treatment groups with regard to laboratory abnormalities, new opportunistic infections, lymphocyte counts, T4 counts, T8 counts, or skin reactivity tests [see ADVERSE REACTIONS].
Table 2: Megestrol Acetate Oral Suspension Clinical
|Megestrol Acetate Oral Suspension Clinical Efficacy Trials|
|Trial 1 - Study Accrual Dates 11/88 to 12/90||Trial 2 - Study Accrual Dates 5/89 to 4/91|
|Megestrol Acetate, mg/day||0||100||400||800||0||800|
|Mean Change in Weight (kg)|
|Baseline to 12 Weeks||0.0||1.3||4.2||4.9||-1.0||5.1|
|% Patients ≥ 2.3 kg Gain at Last Evaluation in 12 Weeks||21||44||57||64||28||47|
|Mean Changes in Body Composition*:|
|Fat Body Mass (kg)||0.0||1.0||1.3||2.5||0.7||2.6|
|Lean Body Mass (kg)||-0.8||-0.1||0.7||1.1||-0.7||-0.3|
|% Patients With Improved Appetite:|
|At Time of Maximum|
|At Last Evaluation in 12 Weeks||50||72||68||89||38||67|
|Mean Change in Daily Caloric Intake:|
|Baseline to Time of Maximum|
|*Based on bioelectrical impedance analysis determinations at last evaluation in 12 weeks.|
Figure 2: Mean Weight Change for Patients Evaluable
for Efficacy in Trial 1
Figure 3: Mean Weight Change for Patients Evaluable
for Efficacy in Trial 2
Last reviewed on RxList: 7/19/2016
This monograph has been modified to include the generic and brand name in many instances.
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