What is Combivir (Lamivudine/Zidovudine?
Combivir is an oral tablet preparation of two nucleoside and nucleotide reverse transcriptase inhibitor (NRTI) medications: lamivudine and zidovudine. Each tablet contains 150 mg of lamivudine and 300mg of zidovudine. The drug is indicated for the treatment of HIV infection in adults and children weighing more than 30 kg; it should be used in combinations with other antiretroviral agents. Combivir is also indicated for post-exposure HIV prophylaxis, both occupational and non-occupational, in combination with other antiretroviral medications.
Dosing & Administration
For the treatment of an HIV infection, the dosage for adults and children is one tablet twice a day. As mentioned above, Combivir medication should be used in combination with other antiretroviral medications.
When used for occupational post-exposure prophylaxis, Combivir drug is used as part of a three-drug combination with a ritonavir-boosted protease inhibitor such as atazanavir, darunavir, fosamprenavir, or lopinavir for a duration of 28 days. Treatment should be initiated within 36 to 72 hours of exposure.
For non-occupational post-exposure prophylaxis, including sexual assault, Combivir is indicated as part of a three-drug regimen in combination with raltgravir, dolutegravir, or with darunavir/ritonavir for a period of 28 days. Prophylaxis should be initiated within 72 hours of exposure or will likely be ineffective.
Combivir should not be used in renal impairment (a creatinine clearance less than or equal to 50mL/min) because both components may require dose adjustments.
Combivir Side Effects
The side effects include the following:
- Immune reconstitution inflammatory syndrome, or IRS;
- loss of body fat;
The list above is not exhaustive. For more information on Combivir’s side effects, refer to the medication’s package insert.
- Combivir is not recommended in patients with hepatic impairment because the zidovudine component may require a dosage adjustment.
- It should be used with caution in patients with risk factors for hepatic impairment, such as alcoholism.
- Severe and even fatal cases of hepatotoxicity or lactic acidosis have been reported in patients using lamivudine and zidovudine, as with other NRTIs, especially in women. Clinicians should maintain a high clinical index of suspicion for hepatotoxicity or lactic acidosis, including hepatic steatosis or hepatomegaly with normal liver enzymes.
- Co-infection with hepatitis B virus (HBV) with HIV requires special attention, and all patients who test positive for HIV infection should be screened for a comorbid HBV infection. Co-infected patients should be started on an antiretroviral regimen targeting both viruses, regardless of CD4 counts or HBV viral loads. Current HIV treatment guidelines should be consulted for appropriate drug regimens.
- Current HIV treatment guidelines also recommend testing HIV-positive patients for the hepatitis C virus (HCV) along with regular ongoing testing for those deemed to be at high risk for HCV infection. If HIV/HCV co-infection is identified, consideration should be given to treating both infections concurrently.
Combivir can interact with drug agents that are antagonistic with zidovudine. It can also interact with sorbitol. There may be other drugs that Combivir interacts with; for more information on this topic, refer to Combivir’s package insert.
Pregnancy & Lactation
Current guidelines should be consulted when treating women in pregnancy. Women should not breastfeed while taking Combivir, since both components are secreted in the breast milk in high concentrations. The CDC recommends that all HIV-positive women, treated or untreated, avoid breastfeeding to prevent vertical transmission of the virus.
Highly active retroviral combination treatment should be used in all pregnant women, regardless of viral load and CD4 count. Significant data from the Antiretroviral Pregnancy Registry has shown that lamivudine (n>5,000) and zidovudine (n>4,100) are not associated with an increased risk of major birth defects compared to the baseline.
In the case of an overdose with Combivir, supportive treatment should be applied as necessary, and the patient should be closely monitored. For information about what to do in case of an overdose with this medication, refer to the medication’s package insert.