MEPRON®
(atovaquone)
Suspension

Absorption of orally administered MEPRON is limited but can be significantly increased when the drug is taken with food. Plasma atovaquone concentrations have been shown to correlate with the likelihood of successful treatment and survival. Therefore, parenteral therapy with other agents should be considered for patients who have difficulty taking MEPRON with food (see CLINICAL PHARMACOLOGY). Gastrointestinal disorders may limit absorption of orally administered drugs. Patients with these disorders also may not achieve plasma concentrations of atovaquone associated with response to therapy in controlled trials.

Based upon the spectrum of in vitro antimicrobial activity, atovaquone is not effective therapy for concurrent pulmonary conditions such as bacterial, viral, or fungal pneumonia or mycobacterial diseases. Clinical deterioration in patients may be due to infections with other pathogens, as well as progressive PCP. All patients with acute PCP should be carefully evaluated for other possible causes of pulmonary disease and treated with additional agents as appropriate.

If it is necessary to treat patients with severe hepatic impairment, caution is advised and administration should be closely monitored.

The importance of taking the prescribed dose of MEPRON should be stressed. Patients should be instructed to take their daily doses of MEPRON with meals, as the presence of food will significantly improve the absorption of the drug.

Atovaquone is highly bound to plasma protein (>99.9%). Therefore, caution should be used when administering MEPRON concurrently with other highly plasma protein-bound drugs with narrow therapeutic indices, as competition for binding sites may occur. The extent of plasma protein binding of atovaquone in human plasma is not affected by the presence of therapeutic concentrations of phenytoin (15 mcg/mL), nor is the binding of phenytoin affected by the presence of atovaquone.

Rifampin:Coadministration of rifampin and MEPRON Suspension results in a significant decrease in average steady-state plasma atovaquone concentrations (see CLINICAL PHARMACOLOGY: Drug Interactions). Alternatives to rifampin should be considered during the course of PCP treatment with MEPRON.

Rifabutin, another rifamycin, is structurally similar to rifampin and may possibly have some of the same drug interactions as rifampin. No interaction trials have been conducted with MEPRON and rifabutin.

It is not known if MEPRON interferes with clinical laboratory test or assay results.

Carcinogenicity studies in rats were negative; 24-month studies in mice showed treatment-related increases in incidence of hepatocellular adenoma and hepatocellular carcinoma at all doses tested which ranged from 1.4 to 3.6 times the average steady-state plasma concentrations in humans during acute treatment of Pneumocystis cariniipneumonia. Atovaquone was negative with or without metabolic activation in the Ames Salmonella mutagenicity assay, the Mouse Lymphoma mutagenesis assay, and the Cultured Human Lymphocyte cytogenetic assay. No evidence of genotoxicity was observed in the in vivo Mouse Micronucleus assay.

Pregnancy Category C. Atovaquone was not teratogenic and did not cause reproductive toxicity in rats at plasma concentrations up to 2 to 3 times the estimated human exposure. Atovaquone caused maternal toxicity in rabbits at plasma concentrations that were approximately one half the estimated human exposure. Mean fetal body lengths and weights were decreased and there were higher numbers of early resorption and post-implantation loss per dam. It is not clear whether these effects were caused by atovaquone directly or were secondary to maternal toxicity. Concentrations of atovaquone in rabbit fetuses averaged 30% of the concurrent maternal plasma concentrations. In a separate study in rats given a single ¹⁴C-radiolabelled dose, concentrations of radiocarbon in rat fetuses were 18% (middle gestation) and 60% (late gestation) of concurrent maternal plasma concentrations. There are no adequate and well-controlled studies in pregnant women. MEPRON should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

It is not known whether atovaquone is excreted into human milk. Because many drugs are excreted into human milk, caution should be exercised when MEPRON is administered to a nursing woman. In a rat study, atovaquone concentrations in the milk were 30% of the concurrent atovaquone concentrations in the maternal plasma.

Evidence of safety and effectiveness in pediatric patients has not been established. A relationship between plasma atovaquone concentrations and successful treatment of PCP has been established in adults (see Table 2). In a study of MEPRON Suspension in 27 HIV-infected, asymptomatic infants and children between 1 month and 13 years of age, the pharmacokinetics of atovaquone were age-dependent (see CLINICAL PHARMACOLOGY: Special Populations). No drug-related treatment-limiting adverse events were observed in the pharmacokinetic study.

Clinical studies of MEPRON did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Because many patients who participated in clinical trials with MEPRON had complications of advanced HIV disease, it was often difficult to distinguish adverse events caused by MEPRON from those caused by underlying medical conditions. There were no life-threatening or fatal adverse experiences caused by MEPRON.

In the dapsone comparative study of MEPRON Suspension, adverse experience data were collected only for treatment-limiting events. Among the entire population (n = 1,057), treatment-limiting events occurred at similar frequencies in patients treated with MEPRON Suspension or dapsone (Table 6). Among patients who were taking neither dapsone nor atovaquone at enrollment (n = 487), treatment-limiting events occurred in 43% of patients treated with dapsone and 20% of patients treated with MEPRON Suspension (P <0.001).In both populations, the type of treatment-limiting events differed between the 2 treatment arms. Hypersensitivity reactions (rash, fever, allergic reaction) and anemia were more common in patients treated with dapsone, while gastrointestinal events (nausea, diarrhea, and vomiting) were more common in patients treated with MEPRON Suspension.

Table 7 summarizes the clinical adverse experiences reported by ≥20% of patients in any group in the aerosolized pentamidine comparative study of MEPRON Suspension (n = 549), regardless of attribution. The incidence of adverse experiences at the recommended dose was similar to that seen with aerosolized pentamidine. Rash was the only individual adverse experience that occurred significantly more commonly in patients treated with both dosages of MEPRON Suspension (39% to 46%) than in patients treated with aerosolized pentamidine (28%). Among patients treated with MEPRON Suspension, there was no evidence of a dose-related increase in the incidence of adverse experiences. Treatment-limiting adverse experiences occurred less often in patients treated with aerosolized pentamidine (7%)than in patients treated with 1,500 mg MEPRON Suspension once daily (25%, P≤0.001) or 750 mg MEPRON Suspension once daily (16%, P = 0.004). The most common adverse experiences requiring discontinuation of dosing in the group receiving 1,500 mg MEPRON Suspension once daily were rash (6%), diarrhea (4%), and nausea (3%). The most common adverse experience requiring discontinuation of dosing in the group receiving aerosolized pentamidine was bronchospasm (2%).

Other events occurring in ≥10% of the patients receiving the recommended dose of MEPRON included sweating, flu syndrome, pain, sinusitis, pruritus, insomnia, depression, and myalgia. Bronchospasm occurred more frequently in patients receiving aerosolized pentamidine (11%) than in patients receiving MEPRON 1,500 mg/day (4%) and MEPRON 750 mg/day (2%).

Neither MEPRON nor aerosolized pentamidine was associated with a substantial change from baseline values in any measured laboratory parameter, nor were there any significant differences in any measured laboratory parameter between MEPRON and aerosolized pentamidine. Some patients had laboratory abnormalities considered serious by the investigator or that contributed to discontinuation of therapy.

Table 8 summarizes all the clinical adverse experiences reported by ≥5% of the study population during the TMP-SMX comparative study of MEPRON (n = 408), regardless of attribution. The incidence of adverse experiences with MEPRON Suspension at the recommended dose was similar to that seen with the tablet formulation of atovaquone.

Although an equal percentage of patients receiving MEPRON and TMP-SMX reported at least 1 adverse experience, more patients receiving TMP-SMX required discontinuation of therapy due to an adverse event. Twenty-four percent of patients receiving TMP-SMX were prematurely discontinued from therapy due to an adverse experience versus 9% of patients receiving MEPRON. Four percent of patients receiving MEPRON had therapy discontinued due to development of rash. The majority of cases of rash among patients receiving MEPRON were mild and did not require the discontinuation of dosing. The only other clinical adverse experience that led to premature discontinuation of dosing of MEPRON by more than 1 patient was vomiting (<1%). The most common adverse experience requiring discontinuation of dosing in the TMP-SMX group was rash (8%).

Laboratory test abnormalities reported for ≥5% of the study population during the treatment period are summarized in Table 9. Two percent of patients treated with MEPRON and 7% of patients treated with TMP-SMX had therapy prematurely discontinued due to elevations in ALT/AST. In general, patients treated with MEPRON developed fewer abnormalities in measures of hepatocellular function (ALT, AST, alkaline phosphatase) or amylase values than patients treated with TMP-SMX.

ULN = upper limit of normal range.

LLN = lower limit of normal range.

Table 10 summarizes the clinical adverse experiences reported by ≥5% of the primary therapy study population (n = 144) during the comparative trial of MEPRON and intravenous pentamidine, regardless of attribution. A slightly lower percentage of patients who received MEPRON reported occurrence of adverse events than did those who received pentamidine (63% vs 72%). However, only 7% of patients discontinued treatment with MEPRON due to adverse events, while 41% of patients who received pentamidine discontinued treatment for this reason (P<0.001). Of the 5 patients who discontinued therapy with MEPRON, 3 reported rash (4%). Rash was not severe in any patient. No other reason for discontinuation of MEPRON was cited more than once. The most frequently cited reasons for discontinuation of pentamidine therapy were hypoglycemia (11%) and vomiting (9%).

Laboratory test abnormalities reported in ≥5% of patients in the pentamidine comparative study are presented in Table 11. Laboratory abnormality was reported as the reason for discontinuation of treatment in 2 of 73 patients who received MEPRON. One patient (1%) had elevated creatinine and BUN levels and 1 patient (1%) had elevated amylase levels. Laboratory abnormalities were the sole or contributing factor in 14 patients who prematurely discontinued pentamidine therapy. In the 71 patients who received pentamidine, laboratory parameters most frequently reported as reasons for discontinuation were hypoglycemia (11%), elevated creatinine levels (6%), and leukopenia (4%).

ULN = upper limit of normal range.

LLN = lower limit of normal range.

In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of MEPRON. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to MEPRON.

There is no known antidote for atovaquone, and it is currently unknown if atovaquone is dialyzable. The median lethal dose is higher than the maximum oral dose tested in mice and rats (1,825 mg/kg/day). Overdoses up to 31,500 mg of atovaquone have been reported. In 1 such patient who also took an unspecified dose of dapsone, methemoglobinemia occurred. Rash has also been reported after overdose.

Dosage

Administration