FORMULATION AND EVALUATION OF TABLETS OF LAMIVUDINE AND ZIDOVUDINE COMBINATION

Abstract

Lamivudine and zidovudine, two widely prescribed anti retroviral drugs are official in IP 2010 and USP 2008.
Combination of lamivudine and zidovudine is a preferred option for treating HIV and AIDS. Though this combination is used
widely, there are only a few combined drug formulations available in the market. The objective of the present study is to develop
tablet formulations containing lamivudine and zidovudine combination and to evaluate the prepared tablets. Tablets each
containing lamivudine (150 mg) and zidovudine (300 mg) were formulated employing commonly used tablet excipients and were
prepared by wet granulation method. All the prepared tablets were evaluated for drug content, hardness, friability, disintegration
time and dissolution rate. All the combined drug tablets containing lamivudine and zidovudine prepared as well as commercial
tablets fulfilled the official (IP 2010) specifications of uncoated tablets with regard to weight variation, hardness, friability, drug
content and disintegration time. Tablets formulated with superdisintegrants, crospovidone and crosscarmellose sodium
disintegrated rapidly within 1 min 30 seconds. Whereas the tablets formulated employing potato starch as disintegrant
disintegrated relatively slowly and the disintegration time of these tablets was in the range 2 min 40 seconds - 4 min 50 seconds.
The dissolution of both the drugs from the tablets formulated depended on the binder and disintegrant used. Lamivudine and
zidovudine dissolution from the tablets followed first order kinetics with correlation coefficient (r) values in the range 0.9284 –
0.9804. Among the four binders, PVP K30 gave relatively rapid and higher dissolution and starch paste (gelatinized starch) gave
low dissolution. The order of increasing dissolution rate (K1) observed with various binders was PVP K30 > Sucrose > Acacia >
Starch paste. The same order was observed with both the drugs. Tablets formulated employing superdisintegrants gave faster
dissolution of the two drugs than those formulated with potato starch as disintegrant. IP 2010 described a dissolution of NLT 70
% in 30 min for lamivudine and NLT 80% in 30 min for zidovudine. All formulated tablets except formulation F4 and commercial
formulation tested fulfilled the official (IP 2010) dissolution rate test specification. Overall, formulations F3, F5 and F6 gave
very rapid dissolution of both the drugs and as such they are considered as best combined drug formulations developed. The
dissolution characteristics of these formulations are better than those of commercial formulations tested. Based on the results
obtained, PVP K30, sucrose and acacia are recommended as binders and crospovidone and crosscarmellose sodium as
disintegrants for the formulation development of combined drug tablets containing lamivudine and zidovudine.