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It has been 24 hours of unprotected intercourse and in most of cases post exposure prophylaxis is recommended for unto 72 hours.
Azihtromycin is an antibiotic, it can prevent common STDs but not HIV (which is a viral infection). Other drug like Ofloxacin for 5 days is usually prescribed for prevention of STDs.

For prevention of HIV infection after unsafe exposure medicines should start with in 72 hours. Medicines like Zidovudine and one more drug from Protease inhibitors are prescribed for about 4 weeks to prevent HIV. These medicines have many side effects and are difficult to tolerate. If you are suspecting HIV in your partner then go to near by PPTCT Center (managed by NACO) and take advise regarding start of medicines. Don't waste your time if risk is high.

Hope I cleared your doubt. Please review if you are satisfied with answer. If you have more questions then you can ask again.

Thanks
Dr. Seikhoo Bishnoi, MD

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