Cimetidine (Page 2 of 5)

Lower Esophageal Sphincter Pressure and Gastric Emptying

Cimetidine has no effect on lower esophageal sphincter (LES) pressure or the rate of gastric emptying.

Pharmacokinetics

Cimetidine is rapidly absorbed after oral administration and peak levels occur in 45 to 90 minutes. The half-life of cimetidine is approximately 2 hours. Blood concentrations remain above that required to provide 80% inhibition of basal gastric acid secretion for 4 to 5 hours following a dose of 300 mg.

The principal route of excretion of cimetidine is the urine. Following oral administration, the drug is extensively metabolized, the sulfoxide being the major metabolite. Following a single oral dose, 48% of the drug is recovered from the urine after 24 hours as the parent compound.

Clinical Trials

Duodenal Ulcer

Cimetidine has been shown to be effective in the treatment of active duodenal ulcer and, at reduced dosage, in maintenance therapy following healing of active ulcers.

Active duodenal ulcer

Cimetidine accelerates the rate of duodenal ulcer healing. Healing rates reported in U.S. and foreign controlled trials with oral cimetidine are summarized below, beginning with the regimen providing the lowest nocturnal dose.

Table 3. Duodenal Ulcer Healing Rates with Various Oral Cimetidine Dosage Regimens *
Regimen 300 mg
four times daily
400 mg
twice daily
800 mg
at bedtime
1600 mg
at bedtime
*
Averages from controlled clinical trials.

week 4

68%

73%

80%

86%

week 6

80%

80%

89%

week 8

92%

94%

A U.S., double-blind, placebo-controlled, dose-ranging study demonstrated that all once-daily at bedtime cimetidine regimens were superior to placebo in ulcer healing and that cimetidine 800 mg at bedtime healed 75% of patients at four weeks. The healing rate with 800 mg at bedtime was significantly superior to 400 mg at bedtime (66%) and not significantly different from 1600 mg at bedtime (81%).

In the U.S. dose-ranging trial, over 80% of patients receiving cimetidine 800 mg at bedtime experienced nocturnal pain relief after one day. Relief from daytime pain was reported in 70% of patients after two days. As with ulcer healing, the 800 mg at bedtime dose was superior to 400 mg at bedtime and not different from 1600 mg at bedtime.

In foreign, double-blind studies with cimetidine 800 mg at bedtime, 79 to 85% of patients were healed at four weeks.

While short-term treatment with cimetidine can result in complete healing of the duodenal ulcer, acute therapy will not prevent ulcer recurrence after cimetidine has been discontinued. Some follow-up studies have reported that the rate of recurrence once therapy was discontinued was slightly higher for patients healed on cimetidine than for patients healed on other forms of therapy; however, the cimetidine-treated patients generally had more severe disease.

Maintenance therapy in duodenal ulcer

Treatment with a reduced dose of cimetidine has been proven effective as maintenance therapy following healing of active duodenal ulcers.

In numerous placebo-controlled studies conducted worldwide, the percent of patients with observed ulcers at the end of one year’s therapy with cimetidine 400 mg at bedtime was significantly lower (10% to 45%) than in patients receiving placebo (44% to 70%). Thus, from 55% to 90% of patients were maintained free of observed ulcers at the end of one year with cimetidine 400 mg at bedtime.

Factors such as smoking, duration and severity of disease, gender, and genetic traits may contribute to variations in actual percentages.

Trials of other anti-ulcer therapy, whether placebo-controlled, positive-controlled or open, have demonstrated a range of results similar to that seen with cimetidine.

Active Benign Gastric Ulcer

Cimetidine has been shown to be effective in the short-term treatment of active benign gastric ulcer.

In a multicenter, double-blind U.S. study, patients with endoscopically confirmed benign gastric ulcer were treated with cimetidine 300 mg four times a day or with placebo for six weeks. Patients were limited to those with ulcers ranging from 0.5 to 2.5 cm in size. Endoscopically confirmed healing at six weeks was seen in significantlya more cimetidine-treated patients than in patients receiving the placebo, as shown below:

Table 4. Rate of Endoscopically Confirmed Gastric Ulcer Healing
Cimetidine Placebo
*
p < 0.05

week 2

14/63 (22%)

7/63 (11%)

total at week 6

43/65 (66%)*

30/67 (45%)

In a similar multicenter U.S. study of the 800 mg at bedtime oral regimen, the endoscopically confirmed healing rates were:

Table 5. Rate of Endoscopically Confirmed Gastric Ulcer Healing
Cimetidine Placebo
*
p = 0.005

total at week 6

63/83 (76%)*

44/80 (55%)

Similarly, in worldwide double-blind clinical studies, endoscopically evaluated benign gastric ulcer healing rates were consistently higher with cimetidine than with placebo.

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