Inturrupted HIV post exposure prophylaxis for one day

Dear Ask The Doctor: I am a junior doctor sir.. i came into contact with hiv blood on 25-12-2011. at that time i have a small 24 hour injury which is 1cmx1cm injury on my right middle finger. i am not sure whether blood came in contact with that wound. I started system exposure prophylaxis with zidovudine and lamivudine at 13th hour of exposure and taking tablets 2 per day. I m using them regularly but on 15th day i missed two doses, and continued later... whether i m on safe side or not as i missed to take tablets on 15th day. Today is my 20th day of drug usage.

Dear Dr.raju: Post exposure prophylaxis with ARVs can reduce the rate of infection after an exposure to HIV by about 79-80%. Since studies have shown that 4 weeks of zidovudine appeared to increase rate of protection, PEP should be administered for 4 weeks, if tolerated. Missing a dose or incomplete PEP will certainly reduce the effectiveness of the treatment. Whether or not you are on the safe side is difficult for me or anyone to comment. I would advice HIV-antibody testing by enzyme immunoassay to monitor for seroconversion after 6 months of the exposure.