I went to Northern India a few years ago climbing, had the most excellent time, but would make a recommendation to you, Im not trying to worry you! OK, Your doctor can sell you (or even give you) an "aids kit" which is quite important if your backpacking in India - it is a foldable sealed kit which contains important medications and sealed equipment in case you need medical attention. Indian hospitals especially those found off the beaten track are a bit more versatile with their recycling of equipment than the guys back home.
On the subject of drugs and customs I was once questioned over the possession of aeriel washing powder but thats another story... I agree with the advice given, keep the labels and have a great time!