Approval was based on results showing that when the drug is used in combination with standard approved therapies (like AZT, ddI, d4T, 3TC) there was potent suppression of HIV replication (sustained reduction in HIV RNA levels) for at least 24 weeks (see PI Perspective 25 for trial results). It is not known if efavirenz will delay progression of disease or death, but ongoing studies will answer this question.
In laboratory studies there is broad cross-resistance (resistance to one drug results in resistance to another) among the three NNRTIs. This means that if someone has developed resistance to one of the drugs, they are unlikely to get any anti-HIV benefit from the other two. There are many drug interactions with efavirenz because it is broken down by an enzyme used by many commonly used drugs (call Project Inform's National HIV/AIDS Treatment Hotline for the Drug Interaction Chart for complete drug interaction information).
The most studied drug interaction with efavirenz is indinavir (Crixivan®). Efavirenz decreases indinavir levels in the blood. Another potentially serious drug interaction is between efavirenz and saquinavir (Fortovase®) where saquinavir levels are decreased 62%. For more information on Efavirenz, call the Project Inform Hotline at 800-822-7422.
The most common side effect of efavirenz is central nervous system (CNS) symptoms, which can range from severe symptoms such as delusions, acute depression and mania (e.g. severe anxiety) to less severe symptoms such as dizziness, lack of concentration, sleeplessness and strange dreams. Most of the reported CNS side effects have been mild to moderate in severity and usually go away after a few weeks. However, if people experience any severe CNS symptoms, they should contact their healthcare provider immediately. It appears that people with a history of mental illness or substance abuse are more likely to develop the more severe CNS side effects. Other reported side effects include rash, nausea, vomiting, headache, fatigue and diarrhea. Some researchers recommend taking an anti-anxiety drug like lorazepam (Ativan®) to reduce CNS symptoms.
The recommended dose of efavirenz for adults is 600mg once daily (it is recommended that efavirenz be taken at night to reduce the likelihood of CNS side effects). Recommended dosing for children is found in the table below.
It is important that efavirenz not be used alone or merely added to a failing regimen as HIV will develop resistance to the drug rapidly. Efavirenz should always be used as part of a combination where at least two of the drugs are new to an individual.
Recommended Dosing for Children over the Age of 3 Years Is Based on Weight
Many people who are dependent upon the AIDS Drug Assistance Program (ADAP) may find that their state ADAP has been unable to add efavirenz to their list of covered drugs, primarily because the drug came to market at an unexpectedly high price.
Project Inform encourages people who are dependent upon ADAP or have no other payment source for their prescription drugs to check with their state ADAP coordinator. That number can be obtained by calling the Access Project at 800-734-7104. If the state is unable to immediately place the drug on formulary, patients should sign up as quickly as possible with Dupont Pharma's Patient Assistance Program, which can be reached at: 1-800-334-4486
In this instance, we believe that complaints about lack of coverage of the drug by ADAP should be generally directed to the manufacturer, Dupont Pharma, and not to the ADAP directors.
As we go to press, the Antiviral Drugs Advisory Committee to the Food and Drug Administration (FDA) recommended that abacavir (Ziagen®) be approved to treat HIV disease for adults and children. Abacavir is expected to be available in pharmacies before the end of the year. Abacavir will be the sixth nucleoside analogue drug to be approved by the FDA, the others being AZT (zidovudine, Retrovir®), ddI (didanosine, Videx®), ddC (zalcitabine, Hivid®), d4T (stavudine, Zerit®) and 3TC (lamivudine, Epivir®). Studies suggest that abacavir has the most potent anti-HIV activity of all the drugs in its class, when used by people who have not previously been on any anti-HIV therapies. However, for people who have developed resistance to multiple previous therapies, the potency of abacavir tends to drop substantially.
The recommended dose of abacavir is 300mg (a single pill) twice a day for a total daily dose of 600mg. When it is used in combination with AZT and 3TC (Combivir®), the total regimen requires only two pills twice a day (four pills total, per day). The simplicity of the regimen is expected to be one of its most attractive features. The recommended dose for children is 8mg/kg taken twice a day. Abacavir can be taken without regards to food. The most common side effects reported in the clinical studies are nausea, fatigue, headaches and diarrhea. A more serious side effect which affects about 3% of people taking abacavir is a hypersensitivity reaction to the drug. This reaction is usually systemic (throughout the body) and includes fevers, malaise, nausea, vomiting and sometimes rash. This reaction appears relatively soon after starting abacavir (about two weeks) and resolves one or two days after stopping the drug. It is important not to try and take abacavir again (re-challenge) if there was hypersensitivity to the drug as the subsequent reaction is potentially fatal.