The effect was similar to that obtained when thiazides are used as a single agent .
Thiazides when given as a second-line drug have a dose related effect to lower blood pressure that is similar to when they are added as a first-line drug .
This means that the BP lowering effect of thiazides is additive .
Loop diuretics appear to have a similar blood pressure lowering effect as thiazides at 1 times the recommended starting dose .
Because of the short duration of the trials and lack of reporting of adverse events , this review does not provide a good estimate of the incidence of adverse effects of diuretics given as a second-line drug
BACKGROUND Diuretics are widely prescribed for hypertension not only as a first-line drug but also as a second-line drug .
Therefore , it is essential to determine the effects of diuretics on blood pressure ( BP ) , heart rate and withdrawals due to adverse effects ( WDAEs ) when given as a second-line drug .
Comparative studies: enalapril versus hydrochlorothiazide as first-step therapy for the treatment of primary hypertension.
Thirty-nine patients were entered into a 12-week , r and omized , double-blind , parallel protocol to assess the safety and efficacy of enalapril ( MK-421 , 10 to 20 mg bid ) , hydrochlorothiazide ( HCTZ , 25 to 50 mg bid ) , or combined drug therapy ( MK-421 + HCTZ ) for the treatment of primary hypertension . Specifically monitored were the effects of each drug program on BP and pulse , serum chemistries , body fluid composition and weight , renal function , and the renin-angiotensin-aldosterone axis . Results indicate that MK-421 , HCTZ , and combined therapy were equally effective in lowering BP ; none of the therapies significantly altered glomerular filtration rate or effective renal plasma flow . Patients on MK-421 experienced no change in volume , an increase in plasma potassium , no change in fractional sodium or potassium excretion , and a decreased urine osmolality associated with an enhanced free-water clearance . Plasma renin activity was increased , plasma angiotensin II was decreased , and plasma aldosterone was unchanged . In contrast , patients on HCTZ developed volume contraction , hypokalemia associated with an increase in fractional sodium and potassium excretion , and an increased urine osmolality associated with a decreased free-water clearance . Plasma renin activity was increased , however , plasma angiotensin II and plasma aldosterone were unchanged . Patients on combined therapy  with MK-421 + HCTZ demonstrated qualitatively similar changes in serum chemistries , body fluid volumes , and renal function compared with patients receiving HCTZ alone , whereas changes in the renin-angiotensin-aldosterone system in these patients were qualitatively similar , but more marked , compared with those occurring in patients receiving MK-421 alone . We conclude that MK-421 is an effective first-step antihypertensive agent that does not produce adverse metabolic , volume , or renal effects
The effect was similar to that obtained when thiazides are used as a single agent .
Thiazides when given as a second-line drug have a dose related effect to lower blood pressure that is similar to when they are added as a first-line drug .
This means that the BP lowering effect of thiazides is additive .
Loop diuretics appear to have a similar blood pressure lowering effect as thiazides at 1 times the recommended starting dose .
Because of the short duration of the trials and lack of reporting of adverse events , this review does not provide a good estimate of the incidence of adverse effects of diuretics given as a second-line drug
BACKGROUND Diuretics are widely prescribed for hypertension not only as a first-line drug but also as a second-line drug .
Therefore , it is essential to determine the effects of diuretics on blood pressure ( BP ) , heart rate and withdrawals due to adverse effects ( WDAEs ) when given as a second-line drug .