Abacavir

Additional information

Antiretrovirals for treatment of HIV are always given as a combination of at least three medicines. Cobicistat is used to boost the effect of other antiretroviral drugs. As studies on HIV patients always include patients receiving combination therapy it is difficult to know which of the studied medicines that cause changes in effect and/or adverse events.

Pharmacokinetics and dosing

In the producer’s résumé, no difference in dosing depending on patient’s sex is recommended [1]. No sex differences were found in a pediatric study (n=69) of abacavir in infants, toddlers or children [2].

Effects

In the clinical studies, no differences in effect of abacavir between men and women have been reported [1, 3-5]. The effects of abacavir was evaluated in a North- and Central American randomized open-label study in HIV-patients treated with abacavir+lamivudine+zidovudine, lamivudine+zidovudine+nelfinavir, or stavudine+lamivudine+nelfinavir (127 men, 127 women)  and no differences in virological or CD4 responses were seen  with either treatment over 96 weeks [3]. In a randomized study of HIV-1-infected adults (1040 men, 328 women) treated with rilpivirine or efavirenz plus tenofovir/emtricitabine, zidovudine/lamivudine or abacavir/lamivudine, no difference in response rate between men and women was seen either [5]. However, in an observational study in East African children (51 boys, 58 girls) treated with efavirenz, lamivudine, and one of abacavir, stavudine, or zidovudine, virological non-suppression was more common in children older than 8 years. In children younger than 8 years, boys had a 5.3 times higher risk than girls [4].

Adverse effects

Differences in adverse events have been described for different antiretroviral regimens, in general women have been reported to have more nausea and gastrointestinal reactions, more lipodystrophy, a higher risk of developing kidney failure but a lower risk of LDL-level increase compared to men [3, 5-7].A North- and Central American randomized open-label study in HIV-patients investigated changes in cholesterol levels over 96 weeks (127 men, 127 women). Treatment with abacavir+lamivudine+zidovudine was associated with less effect on LDL-levels especially in women and black patients, compared to lamivudine+zidovudine+nelfinavir, or stavudine+lamivudine+nelfinavir treatment [3].In a randomized study on HIV-1-infected adults (1040 men, 328 women) treated with rilpivirine or efavirenz plus tenofovir/emtricitabine, zidovudine/lamivudine or abacavir/lamivudine nausea was more common in women than in men in both treatment groups while abnormal dreams/nightmares were more frequent in men [5].In a US randomized open-label study of HIV-positive patients treated with atazanavir/ritonavir or efavirenz in combination with abacavir/lamivudine or tenofovir/emtricitabine (1535 men, 322 women) women treated with abacavir/lamivudine had a higher (32%) safety risk (more gastrointestinal adverse events) compared to men [6]. Self-reported adherence did not differ significantly by sex [6]. 

The risk of severe hypersensitivity reaction to abacavir is high in persons carrying the HLA-B*5701 allele It is recommended that before taking abacavir, HLA-B*5701 screening should be performed in all patients, regardless of sex or ethnicity [1]. It is not known if there is a difference between men and women in the frequency of the allele.

Reproductive health issues

Regarding teratogenic aspects, please consult Janusmed Drugs and Birth Defects (in Swedish, Janusmed fosterpåverkan).

Other information

A retrospective study on the prevalence of highly sensitivity CRP (hsCRP) levels in HIV patients treated with lamivudine and abacavir and/or zidovudine (145 men, 51 women) showed no difference in hsCRP between men and women at baseline. At week 96 higher levels were seen in women compared to men [8]. 

A review has described drug exposure in the genital tract of men and women which is of interest in viral transferal and in effect of pre-exposure prophylactic treatment. In men, concentrations in seminal fluid were described to be highest for nucleoside analogues and lowest for protease inhibitors and efavirenz. Seminal accumulation of raltegravir and maraviroc was defined as moderate.The rank order of accumulation presented in the review is nucleoside/nucleotide reverse transcriptase inhibitors [lamivudine/zidovudine/tenofovir/didanosine > stavudine/abacavir] > raltegravir > indinavir/maraviroc/nevirapine >> efavirenz/protease inhibitors [amprenavir/atazanavir/darunavir > lopinavir/ritonavir > saquinavir] > enfuvirtide. In the female genital tract, the nucleoside analogues also were described as having high accumulation ratios, whereas protease inhibitors have limited penetration; however, substantial variability exists. Second generation non-nucleoside reverse transcriptase inhibitor etravirine, and maraviroc and raltegravir, have been found to demonstrate effective accumulation in cervicovaginal secretions. The rank of accumulation presented in the review is nucleoside/nucleotide reverse transcriptase inhibitor [zidovudine/lamivudine/didanosine > emtricitabine/tenofovir] > indinavir > maraviroc/raltegravir/darunavir/etravirine > nevirapine/abacavir > protease inhibitors [amprenavir/atazanavir/ritonavir] > lopinavir/stavudine/efavirenz > saquinavir [9].