Certain medications need to be taken with plenty of water. Depending on the medication, there are different reasons for this:
- the medication could cause you to become dehydrated (e.g., lithium)
- the medication could damage the kidneys or lead to kidney stones if too much of it reached the kidney at the same time (e.g., cotrimoxazole, indinavir) – water helps to “dilute” the extra medication so that too much medication does not go through the kidneys at once
In general, medications should be taken with a full glass of water, unless your doctor or pharmacist recommends otherwise. If your medication needs to be taken with “plenty of water,” you may need to drink more than a full glass of water with your medication. This varies with the medication, but can be as much as 1.5 L every day, as is recommended for indinavir. Check with your pharmacist to see how much water you should have with your medication.
It is also important to drink enough water throughout the day to avoid dehydration. People’s water needs will vary. If you are producing about 1.5 litres (6 cups) of colourless to pale-yellow urine each day and rarely feel thirsty, you are likely getting enough fluids.