New Anti-HIV Drug Approved by the FDA . . .

The Food and Drug Administration (FDA) recently approved abacavir (Ziagen^®) to treat adults and children with HIV disease. Abacavir is the sixth nucleoside analogue drug approved by the FDA. Studies suggest that abacavir is very potent, especially when used by people not previously on any anti-HIV therapies. Its potency tends to drop for people who have used other anti-HIV therapies and who have developed resistance to more than one nucleo-side analogue drug.

Abacavir's dose recommendation is 300mg (a single pill) twice a day for a total daily dose of 600mg (two pills per day). When abacavir is used in combination with AZT/3TC (Combivir^®), the total daily regimen requires four pills (two pills twice a day). The simplicity of this regimen makes this combination very attractive. However, people weighing less than 110 pounds (50 kilograms) should use Combivir^® with caution. The recommended dose of abacavir for children is 8mg/kg taken twice daily.

Possible Side Effects

The most commonly observed side effects from abacavir include nausea, fatigue, headaches and diarrhea. A more serious side effect affecting about 3% of people taking abacavir is a hypersensitivity reaction to the drug. The reaction usually occurs throughout the body (systemic) and includes fevers, malaise, nausea, vomiting and sometimes a rash. Most symptoms are commonly seen in people with the flu. The hypersensitivity reaction appears relatively soon after starting abacavir (about two weeks) and resolves one or two days after stopping.

It is important NOT to try and take abacavir again if there was initial hypersensitivity. The subsequent reaction is potentially fatal.

Abacavir Recommended Dosing
Regimen	Dosing
Abacavir Alone	2 x 300mg/day
Abacavir + Combivir®	4 x 300mg/day
Children	8mg/kg, twice per day

. . . While Another Awaits Approval

Amprenavir (Agenerase^®), a new protease inhibitor, is currently awaiting FDA approval. Barring no major surprises, amprenavir should be available through pharmacies by late spring. Studies suggest amprenavir has similar potency against HIV as the currently approved protease inhibitors, ritonavir (Norvir^®), indinavir (Crixivan^®), nelfinavir (Viracept^®) and soft gel saquinavir (Fortovase^®). The most common side effects seen with amprenavir include rash, nausea, vomiting and a numbing around the mouth (called oral paresthesia).

In lab studies (test tube studies as opposed to studies in people), amprenavir has a somewhat, but not completely, different pattern of drug resistance than other protease inhibitors. As a result, amprenavir may be useful for some people who have 'failed' at least one other protease inhibitor-containing regimen. Alternatively, if people chose to use amprenavir as their first protease inhibitor, they may be able to successfully switch to another protease inhibitor-containing regimen if their HIV levels (viral load) start to increase while on amprenavir. However, almost all these observations have come from lab studies. Only large studies involving people can answer whether any of these observations are accurate.

Dosing Concerns

One drawback to amprenavir is that to get an effective dose of the drug, a large number of pills must be taken daily. The current formulation requires 16 pills daily based on the dose that will most likely be recommended for approval (1,200mg twice a day; total daily dose of 2,400mg). Not only is the large number of pills a concern but they are large and difficult to swallow.

Amprenavir is currently available through an expanded access program for people who are unable to tolerate or who are are failing to respond to their current anti-HIV therapies. For information about the program, call 1-800-248-9757.

For more information on these or other anti-HIV drugs, call Project Inform's National HIV/AIDS Treatment Hotline at 1-800-822-7422.