LAMIVUDINE

Research Initiative/Treatment Action!, March, 2000

Lamivudine tablets are film-coated, white, and diamond-shaped with the dosage "150" imprinted on one side and "GX CJ7" on the other side. This drug is also available in a flavored solution or in combination with zidovudine in a tablet formulation called "Combivir."

"The discovery of lamivudine's hepatitis-suppressing potential will likely provide Glaxo with a needed boost, since the patent for the anti-ulcer drug Zantac, its No. I product, will soon expire."

Business Week 3526, p. 104, May 21, 1997

Also known as: 3TC

Background and description. Lamivudine received accelerated approval from the US Food and Drug Administration (FDA) in November 1995. The drug is manufactured and distributed by Glaxo Wellcome. Lamivudine is a nucleoside reverse transcriptase inhibitor (NRTI). In combination with other antiretroviral agents, lamivudine can be effective in suppressing viral replication. The drug is also effective in suppressing the Hepatitis B virus (although in a different formulation, Zeffix).

Guidelines classification. The Panel on Clinical Practices for the Treatment of HIV Infection classifies lamivudine as "strongly recommended" when used with stavudine (Zerit) or zidovudine (Retrovir).

Dose. The recommended lamivudine dosing for adults and adolescents (12 to 16 years of age) is 150 mg twice a day. For adults with low body weights (less than 110 lb) the recommended dose is 2 mg/kg twice a day. Dosing should be adjusted in patients with kidney problems (based on creatinine clearance).

Food restrictions. Lamivudine can be taken with or without a meal.

Storage. Tablets should be stored between 36 [degrees] and 86 [degrees] F in a tightly closed container. The solution should also be kept in a tightly closed container and stored between 36 [degrees] and 77 [degrees] F

Side effects and toxicity. Lactic acidosis and severe hepatomegaly (enlarged liver) with steatosis (fatty liver) are rare, but potentially fatal, and have been associated with NRTI use. Lamivudine is considered to have minimal toxicity and few side effects. Some reported side effects include headache, fatigue and nausea.

Drug interactions. There are no known clinically significant drug interactions with lamivudine.

Resistance and cross-resistance. Lamivudine resistance is associated with a mutation at position 184. When used as monotherapy lamivudine results in rapid and uniform resistance, usually within a few weeks. The mutation at position 184 results in 1000-fold resistance to lamivudine. Early reports indicated that the 184 mutation could improve susceptibility to zidovudine; other reports have suggested that lamivudine resistance confers increased fidelity to the reverse transcriptase enzyme and makes the virus less fit or less pathogenic. The validity of these reports has yet to be proven, but their mere existence and the fact that lamivudine has very few side effects and toxicities has led to the widespread use of the drug even in the presence of clear-cut resistance. A mutation at position 333 confers resistance to both zidovudine and lamivudine. A mutation at position 151 is associated with resistance to the entire NRTI class. An insertion at position 69 can also lead to broad NRTI resistance.

Clinical data. Registrational studies for lamivudine noted its efficacy when combined with zidovudine (Retrovir), but subsequent data indicate more potent effects when used in combination with other drug classes (see table on page 5). Studies of patients failing highly active antiretroviral therapy (HAART) with the combination of indinavir (Crixivan)/ zidovudine/ lamivudine report that virologic rebound is at least initially associated with the mutation at position 184 and resistance to lamivudine.

Patient assistance. For those who qualify, Glaxo Wellcome offers a patient assistance program. For more information, call 800.722.9294.