Most Japanese medication is in powdered form or tablets and is often considered to be weaker than in many western countries. The powder is usually in one-dose packets which you take with a glass of water. Doctors will usually prescribe medicine which is covered by your insurance and with which their pharmacy is supplied.
Often you receive a different medication for each symptom you have and may find yourself going home with a bag full of medication just for three or four days. Do not be afraid to ask for clarification about what the medication is and what it is for.