In clinical trials, the drug has either been taken as a daily PrEP dosage or on-demand (event based dosage).You should always take the amount of Truvada PrEP HIV that you have been instructed to by your doctor. The dosage of PrEP HIV you are told to take will be based on your kidney function, medical condition, as well as your response to the treatment. Children may be prescribed a different dosage based on their weight, as their risk profile will differ to adults. You must keep on taking Emtricitabine/Tenofovir (Truvada medication) and any other HIV treatment that you use exactly as prescribed by your doctor. You should never skip any doses. You should also not take more or less Emtricitabine/Tenofovir than prescribed by your healthcare provider, and you should not risk stopping intake, even for a short time, unless you have been told to do by your doctor. Doing so may cause the amount of virus to increase, make the HIV infection more difficult to treat, or worsen side effects.