[CAS NO. 136470-78-5]  Abacavir (1592U89)

Abacavir efficiently inhibits the growth of ATL cell xenografts in NOD/SCID mice. In adults, Abacavir is rapidly absorbed after oral administration, with peak concentrations occurring 0.63-1 hour after dosing. The absolute bioavailability of abacavir is approximately 83%. Abacavir pharmacokinetics are linear and doseproportional over the range of 300-1200 mg/day. The apparent volume of distribution of abacavir after intravenous administration is approximately 0.86 ± 0.15 L/kg, suggesting that abacavir is distributed to extravascular spaces. Binding to plasma proteins is about 50% and is independent of the plasma abacavir concentration. Abacavir is extensively metabolized by the liver; less than 2% is excreted as unchanged drug in the urine. Abacavir is primarily metabolized via two pathways, uridine diphosphate glucuronyltransferase and alcohol dehydrogenase, resulting in the inactive glucuronide metabolite and the inactive carboxylate metabolite. The terminal elimination half-life of abacavir is approximately 1.5 hours. The antiviral effect of abacavir is due to its intracellular anabolite, carbovirtriphosphate (CBV-TP). Abacavir is not significantly metabolized by cytochrome P450 (CYP) enzymes, nor does it inhibit these enzymes.