Misoprostol (Page 2 of 5)

Effects on gastric acid secretion:

Misoprostol, over the range of 50 to 200 mcg, inhibits basal and nocturnal gastric acid secretion, and acid secretion in response to a variety of stimuli, including meals, histamine, pentagastrin, and coffee. Activity is apparent 30 minutes after oral administration and persists for at least 3 hours. In general, the effects of 50 mcg were modest and shorter lived, and only the 200-mcg dose had substantial effects on nocturnal secretion or on histamine and meal-stimulated secretion.

Uterine effects:

Misoprostol Tablets has been shown to produce uterine contractions that may endanger pregnancy. (See boxed WARNINGS.)

Other pharmacologic effects:

Misoprostol Tablets does not produce clinically significant effects on serum levels of prolactin, gonadotropins, thyroid-stimulating hormone, growth hormone, thyroxine, cortisol, gastrointestinal hormones (somatostatin, gastrin, vasoactive intestinal polypeptide, and motilin), creatinine, or uric acid. Gastric emptying, immunologic competence, platelet aggregation, pulmonary function, or the cardiovascular system are not modified by recommended doses of Misoprostol Tablets.

Clinical studies:

In a series of small short-term (about 1 week) placebo-controlled studies in healthy human volunteers, doses of misoprostol were evaluated for their ability to reduce the risk of NSAID-induced mucosal injury. Studies of 200 mcg q.i.d. of misoprostol with tolmetin and naproxen, and of 100 and 200 mcg q.i.d. with ibuprofen, all showed reduction of the rate of significant endoscopic injury from about 70 to 75% on placebo to 10 to 30% on misoprostol. Doses of 25 to 200 mcg q.i.d. reduced aspirin-induced mucosal injury and bleeding.

Reducing the risk of gastric ulcers caused by nonsteroidal anti-inflammatory drugs (NSAIDs):

Two 12-week, randomized, double-blind trials in osteoarthritic patients who had gastrointestinal symptoms but no ulcer on endoscopy while taking an NSAID compared the ability of 200 mcg of Misoprostol Tablets, 100 mcg of Misoprostol Tablets, and placebo to reduce the risk of gastric ulcer (GU) formation. Patients were approximately equally divided between ibuprofen, piroxicam, and naproxen, and continued this treatment throughout the 12 weeks. The 200-mcg dose caused a marked, statistically significant reduction in gastric ulcers in both studies. The lower dose was somewhat less effective, with a significant result in only one of the studies.

Reduction of Risk of Gastric Ulcers Induced by Ibuprofen, Piroxicam, or Naproxen [No. of patients with ulcer(s) (%)]

Therapy Duration
Therapy 4 weeks 8 weeks 12 weeks
*
Statistically significantly different from placebo at the 5% level.
Combined data from Study No. 1 and Study No. 2.

Study No. 1

Misoprostol Tablets 200 mcg q.i.d. (n=74)

1 (1.4)

0

0

1 (1.4) *

Misoprostol Tablets 100 mcg q.i.d. (n=77)

3 (3.9)

1 (1.3)

1 (1.3)

5 (6.5) *

Placebo (n=76)

11 (14.5)

4 (5.3)

4 (5.3)

19 (25.0)

Study No. 2

Misoprostol Tablets 200 mcg q.i.d. (n=65)

1 (1.5)

1 (1.5)

0

2 (3.1) *

Misoprostol Tablets 100 mcg q.i.d. (n=66)

2 (3.0)

2 (3.0)

1 (1.5)

5 (7.6)

Placebo (n=62)

6 (9.7)

2 (3.2)

3 (4.8)

11 (17.7)

Studies No. 1 & No. 2

Misoprostol Tablets 200 mcg q.i.d. (n=139)

2 (1.4)

1 (0.7)

0

3 (2.2) *

Misoprostol Tablets 100 mcg q.i.d. (n=143)

5 (3.5)

3 (2.1)

2 (1.4)

10 (7.0) *

Placebo (n=138)

17 (12.3)

6 (4.3)

7 (5.1)

30 (21.7)

In these trials there were no significant differences between Misoprostol Tablets and placebo in relief of day or night abdominal pain. No effect of Misoprostol Tablets in reducing the risk of duodenal ulcers was demonstrated, but relatively few duodenal lesions were seen.

In another clinical trial, 239 patients receiving aspirin 650 to 1300 mg q.i.d. for rheumatoid arthritis who had endoscopic evidence of duodenal and/or gastric inflammation were randomized to misoprostol 200 mcg q.i.d. or placebo for 8 weeks while continuing to receive aspirin. The study evaluated the possible interference of Misoprostol Tablets on the efficacy of aspirin in these patients with rheumatoid arthritis by analyzing joint tenderness, joint swelling, physician’s clinical assessment, patient’s assessment, change in ARA classification, change in handgrip strength, change in duration of morning stiffness, patient’s assessment of pain at rest, movement, interference with daily activity, and ESR. Misoprostol Tablets did not interfere with the efficacy of aspirin in these patients with rheumatoid arthritis.

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