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9/10/2002

Firm Adds Capsules to Tizanidine Product Line

Cheryl A. Thompson

Elan Pharmaceuticals Inc. has obtained approval from the Food and Drug Administration to market Zanaflex (PDF), or tizanidine hydrochloride, in capsules in addition to the original tablets. The two dosage forms, when taken with food, behave dissimilarly enough that patients who switch between the tablets and capsules may have increased adverse effects or notice a change in when the drug starts to act.

Tizanidine is used to manage the spasms that accompany multiple sclerosis, spinal cord injury, and other conditions in which patients' muscle tone is unusually increased. Under fasting conditions, tizanidine capsules and tablets achieve their highest level in the plasma and leave the general circulation at about the same times. But when taken with food, these characteristics change dramatically. For example, the maximal plasma concentration of tizanidine is 30 percent higher when two 4-mg tablets are ingested with food instead of under fasting conditions but 20 percent lower when two 4-mg capsules are compared under those circumstances. Food also delays the time when the peak plasma concentration occurs—by 25 minutes for the tablets and two to three hours for the capsules. Under fasting conditions, the peak plasma concentration occurs in one hour. The results of sprinkling a capsule's contents on applesauce are more similar to those of the tablet when taken with food than of the intact capsule.

The recommended dosage of the capsules is the same as for the tablets. According to the product's labeling, patients may notice a change in the drug's effect if they switch the way they take it—with food or under fasting conditions—or shift between tablets and capsules when taking the doses with food.

Zanaflex capsules will be available in 2-, 4-, and 6-mg capsules in 150-coung bottles. Although the labeling for the new dosage form was approved on Aug. 29, the company has not announced when it will start distributing the capsules.

Generic versions of tizanidine hydrochloride tablets are available from several companies.