Atovaquone Oral Suspension - Uses, Side Effects, Warnings, and Precautions

Overview:

Atovaquone oral suspension is an antimicrobial agent used to prevent or treat a serious type of lung infection called Pneumocystis pneumonia (PCP). Atovaquone is a medication that helps to stop the symptoms of infection such as fever, cough, tiredness, and shortness of breath. Atovaquone was approved by the Food and Drug Administration (FDA) in May 1999.

What Is the Clinical Use of Atovaquone?

Atovaquone oral solution is a quinone antimicrobial drug that is indicated for:

• Prevention of Pneumocystis jirovecii pneumonia (PCP) in adults and children aged 13 years and above who are unable to tolerate Trimethoprim-Sulfamethoxazole.

• Treatment of mild-to-moderate PCP in adults and children aged 13 years and above who are unable to tolerate Trimethoprim-Sulfamethoxazole.

Dosage and Administration-

Atovaquone is supplied in foil pouches and bottles-

• For the prevention of PCP, 1,500 milligrams (10 milliliters) of Atovaquone once a day with food is used.

• For the treatment of PCP, 750 milligrams (5 milliliters) of Atovaquone twice a day with food for 21 days is used.

What Are the Warnings and Precautions of Atovaquone?

• Risk of Limited Oral Absorption- Absorption of Atovaquone oral suspension is limited, but it can be significantly increased when the drug is administered with food. Failure to administer Atovaquone oral suspension with food can result in lower plasma concentrations, limiting the response to therapy. In this case, therapy with other agents should be considered in patients who have difficulty taking Atovaquone oral suspension with food or in patients who have gastrointestinal disorders that may limit the absorption of oral medications.

• Hepatotoxicity- Cholestatic hepatitis, fatal liver failure, and elevated liver enzymes have been reported in patients treated with Atovaquone.

Drug Interactions-

• Rifampin or Rifabutin- Concomitant administration of Rifampin or Rifabutin and Atovaquone oral suspension is known to reduce its concentrations; hence, it is not recommended to be used at the same time.

• Tetracycline- Concomitant administration of Tetracycline and Atovaquone oral suspension have been associated with reduced plasma concentrations.

• Metoclopramide- Metoclopramide can reduce the bioavailability of Atovaquone, and hence it should be used only if other antiemetics are not available.

• Indinavir- Consequesant administration of Indinavir and Atovaquone did not change Indinavir's steady-state AUC (area under the curve) and Cmax (maximum concentration), yet they resulted in a decreased C-trough (concentration reached by a drug right before the next dose is given) of Indinavir. Therefore, caution must be taken while administering Atovaquone oral suspension with Indinavir due to the decreased trough concentrations of Indinavir. Patients should be monitored for potential loss of efficacy of Indinavir in cases where coadministration with Atovaquone oral suspension is necessary.

Use In Specific Populations-

• Pregnancy- Insufficient data is available to evaluate the use of Atovaquone in pregnant women to identify the risk for miscarriage, major birth defects, and adverse maternal or fetal outcomes. Pregnant women with HIV infected with PCP are more prone to the risk of adverse pregnancy outcomes. Atovaquone given orally to pregnant rats and rabbits during organogenesis did not cause any fetal malformations at plasma concentrations up to three times and 0.5 times, respectively.

• Lactation- Currently, no data is available on the presence of Atovaquone in human milk, the effects on the breastfed child, or milk production. Atovaquone was found in rat milk when lactating rats were given Atovaquone orally. If a drug is present in animal milk, it will likely be present in human milk as well. Because of the chances for HIV-1 (human immunodeficiency virus) transmission to HIV-negative infants, mothers with HIV-1 should not breastfeed if they are taking Atovaquone for the prevention or treatment of PCP.

• Pediatric Use- The safety and effectiveness of Atovaquone in children have not been evaluated yet.

• Geriatric Use- No sufficient information is available to evaluate the difference between effectiveness in older and younger patients.

For Patients:

What Is Pneumocystis Pneumonia?

Pneumocystis pneumonia (PCP) is a serious type of infection that is caused by the fungus Pneumocystis jirovecii. Most people who are affected by PCP have a medical condition that weakens their immune system, like HIV, or take medicines (corticosteroids) that lower their body’s ability to fight germs and recover from the sickness. The symptoms of PCP include fever, chills, cough, difficulty breathing, chest pain, and tiredness. Currently, no vaccines are available to prevent PCP, but it is managed with medications.

Why Is Atovaquone Prescribed?

Atovaquone is used for treating Pneumocystis jiroveci pneumonia in teenagers and adults. Atovaquone is also used for preventing pneumonia in teenagers and adults who cannot take any other medication that is used for preventing pneumonia. Atovaquone comes under a class of medications known as antiprotozoal agents and works by stopping the growth of certain types of protozoa that are responsible for causing pneumonia.

How Should Atovaquone Be Used?

Atovaquone comes in a liquid form to be taken by mouth. When Atovaquone is used for treating pneumonia, it is taken with meals twice daily for 21 days. When Atovaquone is used for preventing pneumonia, it is taken once daily with a meal.

• Patients are advised to take Atovaquone at the same time every day and follow the directions given on the prescription label or ask the doctor or pharmacist to explain any part that is not understandable.

• Atovaquone should be taken exactly as directed. It should not be taken more or less or more often than prescribed by the doctor.

• If the medication is in a bottle, shake the bottle gently each time before using it to mix the medication evenly. A dose-measuring spoon or a cup can be used to measure the correct amount of liquid for each dose.

• If the medication is in a packet, drink the medication directly from the packet or pour the medication into a dosing spoon or cup.

• Take this medication as written in the prescription. It should not be stopped early, even if it is being used to treat pneumonia and the patient feels better already. If a patient stops taking Atovaquone too soon or skips the doses, the infection may not be completely treated, and the patient may not be protected from future infections.

• If a patient has pneumonia, they may also be prone to other types of lung infections, and Atovaquone will not treat these infections. A doctor may prescribe other antibiotics to take along with this medication.

Other Uses-

Atovaquone is also used along with other medications to treat babesiosis (an infectious disease carried by ticks).

What Special Precautions Should Be Followed for Atovaquone?

• If a patient is allergic to Atovaquone, or any of the ingredients present in Atovaquone suspension, it should be informed to the doctor.

• All the prescription and nonprescription medications, vitamins, nutritional supplements, and or any herbal products taken by the patient should be informed to the doctor.

• It is important to mention medications like Rifabutin or Rifampin because the doctor may need to change the doses of medications or monitor the patient carefully for side effects.

• If a patient has or has ever had stomach or intestinal disorders or liver disease, then it should be informed to the doctor.

• If a patient is pregnant, breastfeeding, or planning for pregnancy, then it should be informed to the doctor. If a patient becomes pregnant while taking Atovaquone, contact a doctor immediately.

What Special Dietary Instructions Should Be Followed?

Unless a doctor advises otherwise, continue the normal diet.

What Should Be Done if a Dose Is Missed?

The patient should take the missed dose as soon as they remember it. However, the missed dose can be skipped if it is almost time for the next dose. Take only a partial dose to make up for a missed dose.

What Side Effects Can Atovaquone Cause?

• Nausea.

• Vomiting.

• Diarrhea.

• Headache.

• Dizziness.

• Anxiety.

• Difficulty falling asleep or staying asleep.

• Fever.

• Rash.

• Hives.

• Swelling of the eyes, face, lips, tongue, mouth, or throat.

• Difficulty breathing or swallowing.

• Hoarseness or throat tightness.

Storage and Disposal-

• The medication should be kept in a cool and dry area and away from sunlight.

• Unneeded medication should be disposed of.

• The medication should not be flushed down the toilet instead, contact the local garbage recycling department to dispose of the medication.

What Should Be Done in Case of Overdose?

In case of an overdose, contact the poison control hotline immediately. If the patient has collapsed, had a seizure, has trouble breathing, or cannot be awakened, they should be immediately rushed to a nearby hospital.

Other Information-

• Any medication should only be taken by the person it is prescribed for and not shared with other people.

• The patient should keep a written list of all the prescription and nonprescription drugs they are taking, and it should be brought in each appointment with a doctor.

• The list should always be carried in case of emergencies.

For Doctors:

Indications-

• Prevention of Pneumocystis Jirovecii Pneumonia- Atovaquone oral suspension is indicated for preventing pneumocystis jirovecii pneumonia in adults and adolescents (aged 13 years and above) who cannot tolerate Trimethoprim-Sulfamethoxazole.

• Treatment of Mild-To-Moderate Pneumocystis Jirovecii Pneumonia (PCP)- Atovaquone oral suspension is indicated for treating mild-to-moderate PCP in adults and adolescents (aged 13 years and above) who cannot tolerate Trimethoprim-Sulfamethoxazole.

Limitations of Use:

Clinical experience with Atovaquone for the treatment of PCP has been limited to patients with mild-to-moderate PCP. Treatment for severe episodes of PCP with Atovaquone has not been studied yet. Atovaquone's efficacy in patients failing therapy with Trimethoprim-Sulfamethoxazole has also not been studied.

Dosage and Administration:

• Dosage For the Prevention of PCP- The recommended oral dosage is 1,500 milligrams (10 milliliters) once a day, administered with food.

• Dosage For the Treatment of Mild-to-Moderate PCP- The recommended oral dosage is 750 milligrams (5 milliliters) twice a day, administered with food for 21 days.

Important Administration Instructions:

• Atovaquone oral suspension should be administered with food to avoid low plasma concentrations that limit response to the therapy.

• Open each five milliliters pouch by folding along the dotted line and tearing it open at a horizontal slit as directed by the arrow on the pouch.

• For a five milliliters dose, take the entire contents either by placing directly into the mouth or by dispensing into a dosing spoon (5 milliliters) or a cup before administration by the mouth.

• For a ten-milliliter dose, take the contents of two pouches.

• Gently shake the medication bottle before administering the recommended dosage.

Pharmacodynamics:

Atovaquone is a highly lipophilic drug closely resembling ubiquinone’s structure. The inhibitory effect of Atovaquone can be compared to that of Ubiquinone; it can selectively affect mitochondrial electron transport and parallel processes such as adenosine triphosphate (ATP) and pyrimidine biosynthesis in Atovaquone-responsive parasites. Cytochrome bc1 complex is a highly discriminating molecular target for Atovaquone in plasmodia. No significant risk is present for myelosuppression associated with Atovaquone, which makes it a beneficial therapeutic agent for recipients of bone marrow transplantation.

Mechanism of Action:

The mechanism of action against Pneumocystis carinii has not been studied fully. In Plasmodium species, the site of action is the cytochrome bc1 complex. Numerous metabolic enzymes are linked to the mitochondrial electron transport chain through Ubiquinone. Inhibition of electron transport by Atovaquone will indirectly inhibit these enzymes. The metabolic effects of the blockade can include inhibition of nucleic acid and ATP synthesis. Atovaquone has also shown good in vitro activity against Toxoplasma gondii.

Pharmacokinetics:

• Absorption-The bioavailability of Atovaquone is variable and low and is highly dependent on the formulation and diet. The bioavailability of the suspension increases two-fold when taken with meals. When given with food, the bioavailability is approximately 47 percent. Without food, bioavailability becomes 23 percent.

• The Volume of Distribution- 0.60 to 0.17 liters per kilogram.

• Protein Binding- Atovaquone is vividly bound to plasma proteins (approximately 99.9 percent) over the concentration range of 1 to 90 micrograms per milliliter.

• Metabolism- Some evidence suggests limited metabolism with Atovaquone.

• Route of Elimination-The half-life of Atovaquone is long because of the presumed enterohepatic cycling and fecal elimination. There was little or no excretion of Atovaquone found in the urine (less than 0.6 percent).

• Half-life- 2.2 to 3.2 days.

• Clearance- 10.4 to 5.5 milliliters per minute.

Storage and Handling:

The medication should be stored at 15 degrees Celsius to 25 degrees Celsius. Do not freeze the medication.

Contraindications- Atovaquone oral suspension is contraindicated in patients who develop or have a history of hypersensitivity reactions such as bronchospasm, angioedema, throat tightness, or urticaria with respect to Atovaquone or any other components present in Atovaquone oral suspension.

Clinical Trial-

In two clinical trials, Atovaquone oral suspension was compared with Dapsone or aerosolized Pentamidine in HIV-1-infected adolescents (13 to 18 years) and adult subjects at risk of PCP and unable to tolerate Trimethoprim-Sulfamethoxazole.

• In the Dapsone trial, the patients were given Atovaquone oral suspension (1500 milligrams once daily) for six months. Among patients taking neither Dapsone nor Atovaquone at enrollment, adverse reactions requiring discontinuation of treatment occurred in 43 percent of patients treated with Dapsone and 20 percent of patients treated with Atovaquone oral suspension. Gastrointestinal adverse reactions such as nausea, vomiting, and diarrhea were more frequently reported in patients treated with Atovaquone oral suspension.

• In the Pentamidine trial, patients were given Atovaquone oral suspension once daily (750 milligrams or 1,500 milligrams) or received aerosolized Pentamidine 300 milligrams every four weeks for six months. The adverse reactions requiring discontinuation of dosing in patients receiving Atovaquone oral suspension of 1,500 milligrams once daily were rash (six percent), diarrhea (four percent), and nausea (three percent). The adverse reaction requiring discontinuation of dosing in the group receiving aerosolized Pentamidine was bronchospasm (two percent).

Adverse Effects-

1. More Than Ten Percent-

• Abdominal pain.

• Cough.

• Depression.

• Diarrhea.

• Dyspnea.

• Fever.

• Headache.

• Infection.

• Insomnia.

• Myalgia.

• Nausea.

• Rash.

• Rhinitis.

• Vomiting.

• Weakness.

2. Between One to Ten Percent-

• Amylase increased.

• Anemia.

• Anorexia.

• Anxiety.

• BUN (blood urea nitrogen) or creatinine increased.

• Constipation.

• Dyspepsia.

• Dizziness.

• Hyperglycemia.

• Hypoglycemia.

• Hyponatremia.

• Liver enzymes elevated.

• Neutropenia.

• Pruritus.

• Oral moniliasis.

• Taste perversion.

Non-Clinical Toxicology-

Carcinogenicity studies in rats were found negative, but 24-month studies in mice (dosed with 50, 100, or 200 milligrams per kilogram per day) showed a treatment-related increase in the incidence of hepatocellular carcinoma and hepatocellular adenoma at all doses tested, which correlated with the average steady-state plasma concentrations (1.4 to 3.6 times) in humans during the treatment of PCP. Atovaquone was found to be 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 found in the in vivo mouse micronucleus assay.