Many prescription and nonprescription medicines can cause dehydration or make it worse. At first you may feel thirsty, have a dry mouth, sticky saliva, and a reduced urine output with dark yellow urine. As dehydration gets worse, you may notice that your urine is very dark or concentrated, your mouth and eyes feel very dry, and you may feel faint when you stand up.

Medicines that can cause dehydration include:

• Antihistamines, such as Benadryl and Chlor-Trimeton.
• Blood pressure medicines, such as Tenormin, Lopressor, Capoten, or Calan.
• Chemotherapy, such as cytoxan or 5-FU.
• Diuretics, such as Lasix or Diuril.
• Laxatives, such as Fleet Phospho-Soda or Correctol.
• Psychiatric medicines, such as Risperdal or Seroquel.

If you think that your dehydration is caused by a medicine:

• Call the doctor who prescribed the medicine to find out if you should stop taking it or take a different one. An appointment may not be necessary.
• If you are taking a nonprescription medicine, stop taking it. Call your doctor if you feel you need to continue taking the medicine.