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The combination of potassium-sparing diuretics with hydrochlorothiazideis extensively
used by hypertensive patients. In the United States, a capsule formulation containing
50 mg triamterene and 25 mg hydrochlorothiazide (Dyazide) is the most popular fixedcombination
product. However, several investigators have confirmed that absorption of both the
triamterene and hydrochlorothiazide components of Dyazide is markedly reduced. This
reduced bioavailability may reduce its effectiveness in hypertensive patients who
change from optimally bioavailable hydrochlorothiazide tablets to Dyazide capsules
in an effort to correct hypokalemia. Scored tablets containing 75 mg triamterene/50
mg hydrochlorothiazide (Maxzide) have been developed using a patented parallel granulation
manufacturing process and evaluated in a series of bioavailability-bioequivalence
studies. The triamterene and hydrochlorothiazide components of Maxzide tablets were
found to be as bioavailable as liquid preparations of the active ingredients given
singly or in combination. Unlike Dyazide capsules, the hydrochlorothiazide component
of Maxzide tablets was found to be absorbed to the same extent as single-entity hydrochlorothiazide
tablets. These studies demonstrated that two Dyazide capsules (total of 100 mg triamterene/50
mg hydrochlorothiazide) deliver to the bloodstream approximately one-half the quantity
of hydrochlorothiazide as one Maxzide (75 mg triamterene/50 mg hydrochlorothiazide)
tablet or one 50 mg hydrochlorothiazide tablet. Similarly, two Dyazide capsules deliver
approximately one-half the quantity of triamterene as one Maxzide tablet. The safety
of Maxzide tablets (dose of one tablet a day) was then evaluated in three groups of
hypertensive patients: those who previously had been given two Dyazide capsules a
day, those who had received four Dyazide capsules a day, and newly diagnosed patients
who had received no medication. The clinical condition of the patients who changed
from two or four Dyazide capsules to one Maxzide tablet was not compromised. Indeed,
significant reductions in blood pressures were observed, especially in some patients
who had remained hypertensive while receiving Dyazide. As expected, the blood pressures
of the previously untreated group also decreased significantly with Maxzide tablets.
Clinically significant hyperkalemia or hypokalemia did not develop. There were no
clinically significant changes in blood urea nitrogen, creatinine, or uric acid levels.
In addition to enhanced bioavailability, Maxzide tablets offer the advantages of once-a-day
dosing.
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© 1984 Technical Publishing, a Division of Dun-Donelley Publishing Corp., a Company of the Dun & Bradstreet Corporation—all rights reserved. Published by Elsevier Inc.
