After weeks of therapy, more patients who received the combination regimen reached target diastolic blood pressure than those who received the monotherapy regimen 29. More Wed, 24 Jun 2009 Clinical Trials Update: June 23, 2009HealthDay HealthDay News -- Here are the latest clinical trials, courtesy of CenterWatch and ClinicalConnection. What is losartan? Losartan is in group of drugs called pilule losartan angiotensin II receptor antagonists. What are the possible side effects of losartan? Get emergency medical help if you have any of these signs of an allergic reaction: difficulty swelling of your face, lips, tongue, or throat. Special warnings about Losartan potassium and Hydrochlorothiazide If you are taking Hyzaar and have kidney disease, your doctor will watch your kidney function carefully. There was essentially no change in average heart rate in losartan-treated patients in controlled trials.