How do the medications interact with each other?
|Author:||Bichet, Daniel G.|
Amiloride also causes the body to excrete more sodium in the urine. This also results in reduced extracellular sodium and fluid volume. But amiloride has its effect at a different part of the kidney than hydrochlorothiazide. So when the two drugs are used together, they both, working at different locations, cause increased sodium excretion, which changes the osmotic conditions to allow increased absorption of body water at different places in the kidney than the NDI-impaired collecting duct.
Indomethacin, on the other hand, works to reduce urine output by inhibiting prostaglandin synthesis in the kidney. Prostaglandins inhibit the hydroosmotic effect of AVP in the collecting duct. By blocking the action of prostaglandin in the collecting duct, indomethacin enhances the ability of AVP to concentrate urine.
Since the combination of amiloride and hydrochlorothiazide is as effective as the combination of indomethacin and hydrochlorothiazide, and since amiloride has fewer and milder side-effects than indomethacin and hydrochlorothiazide, most clinicians prefer amiloride, reserving indomethacin for emergency uses since its action begins more quickly than the diuretics.