Side-effects

The most common side-effects of abacavir (Ziagen) are nausea, vomiting, lethargy, and fatigue. Other commonly reported side-effects are fever, headache, diarrhoea, and loss of appetite. In general, symptoms appear in the first few weeks of treatment, are mild to moderate in severity, and tend to resolve on their own.

Abacavir seems to be less damaging to mitochondria than some of the other nucleoside reverse transcriptase inhibitors (NRTIs), such as d4T (stavudine, Zerit) and AZT (zidovudine, Retrovir).1 It is therefore less likely than some of the other NRTIs,  to cause side-effects related to mitochondrial damage, such as fat loss from under the skin.2 A number of studies have examined the effects of switching from these drugs to abacavir, with most showing modest improvements in fat levels.3 4 5

There is conflicting evidence as to whether abacavir increases the risk of myocardial infarction. Recent data on this issue are presented in the following section, Risk of cardiovascular disease.

Lactic acidosis is a rare, but serious side-effect of all NRTIs including abacavir. Symptoms include an enlarged and tender liver, nausea, and malaise. Lactic acidosis usually develops within a few months of starting treatment with NRTIs. This side-effect seems to occur more commonly in women and in individuals with existing liver disease or who are obese.

Liver toxicity was reported in two women ten to 12 weeks after switching to an abacavir-containing regimen. Neither had underlying risk factors for liver disease and both tested HLA-B*5701 negative before starting the drug. Laboratory values were normal at six weeks, but alanine aminotransferase (ALT) were well over five times the upper limit of normal a short time later. The one biopsy done found severe inflammation in one women. Hypersensitivity reaction and hepatitis were both ruled out as causative agents. Lab values returned to normal and Inflammation resolved after treatment with abacavir was stopped. The authors point out that even minor symptoms after starting therapy should be reported and investigated.6

Three case reports of changes in mental state in patients starting abacavir have been reported. Although rare, symptoms include depression, suicidal thoughts, auditory hallucinations, psychosis, headaches and nightmares.7 8 9

References

  1. Hoy JF et al. Changes in mitochondrial DNA in peripheral blood mononuclear cells from HIV-infected patients with lipoatrophy randomized to receive abacavir. J Infect Dis 190(4): 688-692, 2004
  2. Podzamczer D et al. Less lipoatrophy and better lipid profile with abacavir as compared to stavudine: 96-week results of a randomized study. J Acquir Immune Defic Syndr 4(2):139-147, 2007
  3. Martin A et al. Reversibility of lipoatrophy in HIV-infected patients 2 years after switching from a thymidine analogue to abacavir: the MITOX Extension Study. AIDS 18: 1029-1036, 2004
  4. Katlama C et al. Comparison of metabolic abnormalities 48 weeks after switching from highly active antiretroviral therapy containing non-nucleoside reverse transcriptase inhibitor to Trizivir versus continued highly active antiretroviral therapy. AIDS 17: 1855-1856, 2003
  5. Moyle G et al. A 48 week, randomized, open label comparison of three abacavir-based substitution approaches in the management of dyslipidemia and peripheral lipoatrophy. J Acquir Immune Defic Syndr 33: 22-28, 2003
  6. Soni S et al. Abacavir-induced hepatotoxicity: a report of two cases. AIDS 22(18): 2557-2258, 2008
  7. Colebunders R et al. Neuropsychiatric reaction induced by abacavir. Am J Med 113: 616, 2002
  8. Foster R et al. Antiretroviral therapy-induced psychosis: case report and brief review of the literature. HIV Med 4: 139-144, 2003
  9. Foster R et al. More on abacavir-induced neuropsychiatric reactions. AIDS 18: 2449, 2004
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