Common Side Effects
- During clinical trials, more than 10 percent of patients taking atovaquone reported nausea, minor rash, diarrhea, insomnia, headache, vomiting, fever, cough, abdominal pain, sweating, general pain and oral yeast infections. These problems led as many as 24 percent of patients to stop or temporarily suspend atovaquone use.
Less-Common Side Effects
- Between 1 percent and 10 percent atovaquone-treated patients participating in clinical trials experienced general weakness (e.g., asthenia), dizziness, anxiousness, loss of appetite, sinusitis, upset stomach, nasal irritation, changes in taste sensation, low blood pressure and low blood sugar. Some patients also experienced anemia, decreased white blood cell counts (i.e., neutropenia) and elevated liver enzymes, blood sugar and phosphates.
Serious Side Effects of Unknown Frequency
- The prescribing information for atovaquone includes a list of side effects reported for patients taking atovaquone after the medication was approved by the U.S. Food and Drug Administration. This list includes decreases in red blood cell counts (i.e., thrombocytopenia), pancreatitis, severe rash, kidney damage and allergic reactions marked by throat and heart swelling. The percentages of patients who have had these problems are not reported.
- Because rare cases of liver damage have been reported for patients taking atovaquone, doctors need to prescribe the medication cautiously for patients with severely impaired liver function.
- Administering rifampin (e.g., Rifadin from sanofi aventis) or rifabutin (Mycobutin from Pfizer) can lower the concentrations of atovaquone in patients' bloodstream. Conversely, administering atovaquone can lower the concentrations of zidovudine (e.g., Retrovir from GlaxoSmithKline) and sulfa drugs such as sulfamethoxazole-trimethoprim (e.g., Bactrim from Mutual).
- Patients should take no more than 1,500 mg of atovaquone each day. Patients who have taken more than this amount of atovaquone have developed a rash and a potentially fatal blood disorder known as methemoglobinemia in the body becomes unable to breakdown and eliminate old red blood cells.