abacavir sulfate
Ziagen

Available forms
Available by prescription only
Oral solution: 20 mg/ml
Tablets: 300 mg

Indications and dosages
 HIV-1 infection. Adults: 300 mg P.O. b.i.d. with other antiretrovirals.
Children ages 3 months to 16 years: 8 mg/kg P.O. b.i.d. (up to maximum of 300 mg P.O. b.i.d.) with other antiretrovirals.

Pharmacodynamics
Antiviral action: Converted intracellularly to the active metabolite carbovir triphosphate, which inhibits the activity of HIV-1 reverse transcriptase by competing with the natural substrate deoxyguanosine-58-triphosphate and by incorporation into viral DNA.

Pharmacokinetics
Absorption: Rapidly and extensively absorbed after oral administration; mean absolute bioavailability of the tablet is 83%.
Distribution: Distributed in the extravascular space. About 50% of drug binds to plasma proteins.
Metabolism: Primarily metabolized by alcohol dehydrogenase and glucuronyl transferase to form two metabolites that lack antiviral activity.
Excretion: Primarily excreted in urine; about 16% in feces. Elimination half-life in single-dose studies is 1 to 2 hours.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug or its components. Use cautiously in patients with risk factors for liver disease.

Interactions
Drug-lifestyle. Alcohol use: Reduces abacavir elimination, increasing overall exposure to drug. Monitor patient’s alcohol consumption, and discourage alcohol use.

Adverse reactions
CNS: insomnia, sleep disorders, headache, fever.
GI: nausea, vomiting, diarrhea, loss of appetite.
Metabolic: mild hyperglycemia.
Skin: rash.
Other: hypersensitivity reaction.

Effects on lab test results
• May increase GGT and triglyceride levels.

Overdose and treatment
There’s no known antidote, and it isn’t known whether the drug is removed by peritoneal dialysis or hemodialysis.

Special considerations
• Abacavir should always be used with other antiretrovirals and shouldn’t be added as a single drug when an antiretroviral regimen is changed because of loss of virologic response.
• Lactic acidosis and severe (even fatal) hepatomegaly with steatosis have been reported with use of nucleoside analogues alone or in combination, including abacavir and other antiretrovirals. These conditions may also occur in patients with no risk factors for liver disease. Stop treatment if a patient develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
• Because the drug is absorbed equally well from both dosage forms, solution and tablets can be used interchangeably.
 ALERT The drug has caused fatal hypersensitivity reactions. If evidence of hypersensitivity (fever, rash, fatigue, or GI symptoms such as nausea, vomiting, diarrhea, or abdominal pain) develops, discontinue drug as soon as a reaction is suspected and provide immediate medical attention.
 ALERT Don’t start drug after a hypersensitivity reaction because more severe symptoms will recur within hours and may include life-threatening hypotension and death. Symptoms usually appear within the first 6 weeks of treatment but may occur at any time.
• To facilitate reporting of hypersensitivity reactions and collection of information on each case, the Abacavir Hypersensitivity Registry has been established at 1-800-270-0425.
Pregnant patients
• There are no adequate controlled studies in pregnant women. Report maternal-fetal outcomes of pregnant women exposed to drug to the Antiretroviral Pregnancy Registry at 1-800-258-4263.
Breast-feeding patients
• Because of the risk of HIV transmission through breast-feeding and because of the possible adverse effects of abacavir, women shouldn’t breast-feed if receiving this drug.
Pediatric patients
• Safety and efficacy haven’t been established in children ages 3 months to 13 years.
Geriatric patients
• Dose selection for geriatric patients should be cautious, taking into account the increased likelihood of decreased hepatic, renal, or cardiac function and of concomitant disease or other drug therapy.

Patient education
• Advise patient to take drug exactly as prescribed.
• Urge patient to read the medication guide that comes with each new prescription and refill.
• Tell patient that the drug may be taken without regard to meals.
• Advise patient about the risk of a life-threatening hypersensitivity reaction with this drug.
• Tell patient to immediately report any signs or symptoms of hypersensitivity, including fever, rash, severe tiredness, GI symptoms (such as nausea, vomiting, diarrhea, or stomach pain), achiness, or a generally ill feeling.
• Instruct patient to carry a medical identification card that summarizes the symptoms of the hypersensitivity reaction.
• Explain that this drug doesn’t cure HIV infection or reduce the risk of transmitting HIV to others through sexual contact or blood contamination. Advise patient to remain under medical care throughout drug therapy and to practice safe sex.
• Inform patient that long-term effects of this drug are unknown.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use