I have white patches in back of throat but no pain. what could it be? ii was on anti biotics for separate problem.could the medicine have caused it?.

Get it checked: The way you describe it could be candida. Get it checked by a doc. Fungal infection after broad-spectrum antibiotics is a possibility. But usually does not happen with regular course of antibiotics for a person who is not immunocompromised. If it is candida, it may resolve spontaneously in a couple of weeks...But again better to have it checked.

Evaluation: The white patches could be anything from yeast infection (candida) to leukoplakia to nicotinic stomatitis. In other words, there are many possibilities in the list of differential diagnosis so it's important for proper evaluation.