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Executive Summary

PENNWALT's NEW LOW DOSE METOLAZONE MICROX FOR HYPERTENSION was approved by FDA Oct. 30 via a full NDA. Microx (metolazone .5 mg tab) is indicated for "the treatment of hypertension, alone or in combination with other antihypertensive drugs of a different class," according to approved labeling. Microx is a more bioavailable version of the company's higher dose metolazone (2.5, 5 and 10 mg) product, Zaroxolyn, which is indicated for edema accompanying congestive heart failure and renal failure as well as hypertension. Microx labeling notes that the product is "a rapidly available formulation of metolazone for oral administration." Microx, labeling states, is "not therapeutically equivalent to Zaroxolyn tablets and other formulations of metolazone that share its slow and incomplete bioavailability." In connection with the Microx approval, Zaroxolyn labeling was revised to note that Microx is a more bioavailable product and that it should be used for new hypertension patients. Serale also markets a version of the higher dose metolazone product (Diulo) under a licensing agreement with Pennwalt. Promotional material describing Microx highlights the diuretic/antihypertensive's low dose, low side effect profile, and price advantage compared to other antihypertensive therapies. A fact sheet on Microx developed for the trade states that the product was developed "in response to concerns" over "the antihypertensive dose response curve for diutetics." In developing Microx, "Pennwalt utilized dose response studies to identify for Microx a dose that produces an optimal balance between efficacy and potassium loss." The sheet adds that "in double-blind, multi-center studies a single daily dose of Microx .5 mg was found to control blood pressure in a majority of patients with mild to moderate hypertension while maintaining a mean serum potassium level of 4.0 mEq/L (3.5 mEq/L to 4.5 mEq/L is considered normal)." The trade information also notes that Microx will be priced "well below beta blockers, calcium channel blockers, ACE inhibitors and other branded diuretics." Pennwalt sent approval announcements and fact sheets to the trade on Nov. 3 and will begin shipping the product the week of Nov. 16. Price to wholesalers is $19.98 for a bottle of 100 tablets. Microx is Pennwalt's third cardiovascular product. In addition to Zaroloxyn, the company markets Hylorel (guanadrel sulfate), indicated for hypertension. The Microx product information sheet notes that "Pennwalt will put a vast majority of its field selling and promotional resources behind Microx . . . [and projects that it will] be its largest dollar volume product within two-to-three years." Pennwalt, which did approximately $125 mil. in pharmaceutical sales in 1986, plans to begin journal advertisements and other promotions for Microx in January. The company noted that it has filed for three years exclusivity for Microx, under provisions of the Waxman/Hatch law. Pennwalt does not intend to license the product to other U.S. pharmaceutical firms. The new metolazone formulation is currently approved for use in the U.S. only.

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