The aims of this study were to analyze the prescription pattern of desmopressin before and after the new indication was approved for treatment of nocturia in the elderly in Sweden in 2002 and to analyze to what extent other drugs potentially inducing hyponatremia were prescribed in combination with desmopressin. We conducted epidemiological analyzes of the Swedish Prescribed Drug Register from 2000 to March 2007. All patients older than 60 years who were prescribed desmopressin in Sweden during the study period were included. A marked increase in filled prescriptions of desmopressin in elderly patients was noticed after the new approval in 2002. The therapeutic intensity peaked in 2005 and has thereafter markedly decreased. The magnitude of concurrent treatment with any of the following drugs was assessed: diuretics, tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRI), chlorpromazine, carbamazepine, loperamide, and nonsteroid anti-inflammatory drugs. More than half of the patients on desmopressin during July 2005 and March 2007 filled a prescription of any of the potentially harmful drugs within 30 days of a filled prescription of desmopressin. The use of desmopressin in the elderly after the new approval in 2002 showed a similar prescription pattern to any newly introduced drug or after a changed indication. A large part of the elderly on desmopressin also receives other drugs that are potentially harmful in combination with desmopressin. Increased awareness of potentially interacting concomitant medication can improve medication safety in this fragile group.