Atovaquone

Atovaquone has not been specifically studied in patients with significant hepatic or renal impairment. If it is necessary to treat such patients with atovaquone, caution is advised and administration should be closely monitored.

When given with efavirenz or boosted protease-inhibitors, atovaquone concentrations have been observed to decrease as much as 75%. This combination should be avoided whenever possible.

The co-administration of atovaquone at doses of 45 mg/kg/day in children (n=9) with acute lymphoblastic leukaemia for prophylaxis of PCP was found to increase the plasma concentrations (AUC) of etoposide and its metabolite etoposide catechol by a median of 8.6% and 28.4% (respectively compared to the co-administration of etoposide and sulfamethoxazole-trimethoprim). Caution should be advised in patients receiving concomitant therapy with etoposide.

Concomitant administration of atovaquone and indinavir in clinical trials results in a significant decrease in the C_min of indinavir (23% decrease; 90% CI 8-35%) and the AUC (9% decrease; 90% CI 1-18%). Caution should be exercised on the potential risk of failure of indinavir treatment if co-administered with atovaquone.

Concurrent use of metoclopramide is not recommended. Concomitant treatment with metoclopramide has been associated with a significant decrease (about 50%) in plasma concentrations of atovaquone. Another antiemetic treatment should be given.

In clinical trials small decreases in plasma concentrations of atovaquone (mean <3 µg/ml) were associated with concomitant administration of paracetamol, benzodiazepines, acyclovir, opiates, cephalosporins, anti-diarrhoeals and laxatives. The causal relationship between the change in plasma concentrations of atovaquone and the administration of the drugs mentioned above is unknown.

Concomitant administration of rifampicin or rifabutin is not recommended as it is known to reduce plasma concentrations of atovaquone levels by approximately 50% and 34%, respectively.

Patients receiving concurrent tetracycline should be closely monitored. Concomitant treatment with tetracycline has been associated with decreases in plasma concentrations of atovaquone.

There is no information on the effects of atovaquone administration during human pregnancy. Atovaquone should not be used during pregnancy unless the benefit of treatment to the mother outweighs any possible risk to the developing foetus.

Insufficient data are available from animal experiments to assess the possible risk to reproductive potential or performance.

It is not known whether atovaquone is excreted in human milk, and therefore breast-feeding is not recommended.

There have been no studies to investigate the effect of atovaquone on driving performance or the ability to operate machinery but a detrimental effect on such activities is not predicted from the pharmacology of the drug.

Patients participating in clinical trials with atovaquone have often experienced undesirable effects consistent with the course of advanced Human Immunodeficiency Virus (HIV) disease or of concomitant therapy. The following adverse reactions have been observed and reported to have a suspected (at least possible) causal relationship to treatment with atovaquone with the following frequencies:

The following convention is used for frequencies: very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1 000 to <1/100); rare (≥1/10 000 to <1/1 000); very rare (<1/10 000); not known (cannot be estimated from the available data).

Blood and the lymphatic system disorders

Common: anaemia, neutropenia

Metabolism and nutrition disorders

Common: hyponatraemia

Psychiatric disorders

Common: insomnia

Nervous system disorders

Common: headache

Gastrointestinal disorders

Very common: nausea

Common: diarrhoea, vomiting

Hepatobiliary disorders

Common: elevated liver enzymes levels

Immune System Disorders

Common: hypersensitivity reactions including angioedema, bronchospasm and throat tightness

Skin and subcutaneous tissue disorders

Very common: rash, pruritus

Common: urticaria

Not known: erythema multiforme, Stevens-Johnson Syndrome

General disorders and administration site conditions

Common: fever

Investigations

Uncommon: elevated amylase levels