DOSAGE AND ADMINISTRATION
Active Duodenal Ulcer: Clinical studies have indicated that suppression of nocturnal acid is the most important factor in duodenal ulcer healing (see Clinical Pharmacology -Acid Secretion). This is supported by recent clinical trials (see Clinical Trials - Active Duodenal Ulcer). Therefore, there is no apparent rationale, except for familiarity with use, for treating with anything other than a once-daily at bedtime dosage regimen (h.s.).
In a U.S. dose-ranging study of 400 mg h.s., 800 mg h.s. and 1600 mg h.s., a continuous dose response relationship for ulcer healing was demonstrated.
However, 800 mg h.s. is the dose of choice for most patients, as it provides a high healing rate (the difference between 800 mg h.s. and 1600 mg h.s. being small), maximal pain relief, a decreased potential for drug interactions (see Precautions - Drug Interactions) and maximal patient convenience. Patients unhealed at 4 weeks, or those with persistent symptoms, have been shown to benefit from 2 to 4 weeks of continued therapy.
It has been shown that patients who both have an endoscopically demonstrated ulcer larger than 1.0 cm and are also heavy smokers (i.e., smoke one pack of cigarettes or more per day) are more difficult to heal. There is some evidence which suggests that more rapid healing can be achieved in this subpopulation with Tagamet 1600 mg at bedtime. While early pain relief with either 800 mg h.s. or 1600 mg h.s. is equivalent in all patients, 1600 mg h.s. provides an appropriate alternative when it is important to ensure healing within 4 weeks for this subpopulation. Alternatively, approximately 94% of all patients will also heal in 8 weeks with Tagamet 800 mg h.s.
Other Tagamet regimens in the U.S. which have been shown to be effective are: 300 mg four times daily, with meals and at bedtime, the original regimen with which U.S. physicians have the most experience, and 400 mg twice daily, in the morning and at bedtime (see Clinical Trials - Active Duodenal Ulcer).
Concomitant antacids should be given as needed for relief of pain. However, simultaneous administration of Tagamet and antacids is not recommended, since antacids have been reported to interfere with the absorption of Tagamet (cimetidine).
While healing with Tagamet often occurs during the first week or two, treatment should be continued for 4 to 6 weeks unless healing has been demonstrated by endoscopic examination.
Maintenance Therapy for Duodenal Ulcer: In those patients requiring maintenance therapy, the recommended adult oral dose is 400 mg at bedtime.
ACTIVE BENIGN GASTRIC ULCER
The recommended adult oral dosage for short-term treatment of active benign gastric ulcer is 800 mg h.s., or 300 mg four times a day with meals and at bedtime. Controlled clinical studies were limited to 6 weeks of treatment (see Clinical Trials). 800 mg h.s. is the preferred regimen for most patients based upon convenience and reduced potential for drug interactions. Symptomatic response to Tagamet does not preclude the presence of a gastric malignancy. It is important to follow gastric ulcer patients to assure rapid progress to complete healing.
EROSIVE GASTROESOPHAGEAL REFLUX DISEASE (GERD)
The recommended adult oral dosage for the treatment of erosive esophagitis that has been diagnosed by endoscopy is 1600 mg daily in divided doses (800 mg b.i.d. or 400 mg q.i.d.) for 12 weeks. The use of Tagamet beyond 12 weeks has not been established.
PREVENTION OF UPPER GASTROINTESTINAL BLEEDING
The recommended adult dosing regimen is continuous I.V. infusion of 50 mg/hour. Patients with creatinine clearance less than 30 cc/min. should receive half the recommended dose. Treatment beyond 7 days has not been studied.
PATHOLOGICAL HYPERSECRETORY CONDITIONS
(such as Zollinger-Ellison Syndrome)
Recommended adult oral dosage: 300 mg four times a day with meals and at bedtime. In some patients it may be necessary to administer higher doses more frequently. Doses should be adjusted to individual patient needs, but should not usually exceed 2400 mg per day and should continue as long as clinically indicated.
In hospitalized patients with pathological hypersecretory conditions or intractable ulcers, or in patients who are unable to take oral medication, Tagamet may be administered parenterally.
The doses and regimen for parenteral administration in patients with GERD have not been established.
All parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration.
RECOMMENDATIONS FOR PARENTERAL ADMINISTRATION:
Intramuscular injection: 300 mg q 6 to 8 hours (no dilution necessary). Transient pain at the site of injection has been reported.
Intravenous injection: 300 mg q 6 to 8 hours. In some patients it may be necessary to increase dosage. When this is necessary, the increases should be made by more frequent administration of a 300 mg dose, but should not exceed 2400 mg per day. Dilute Tagamet (cimetidine hydrochloride) Injection, 300 mg, in Sodium Chloride Injection (0.9%) or another compatible I.V. solution (see Stability of Tagamet Injection) to a total volume of 20 mL and inject over a period of not less than 5 minutes (see Precautions).
Intermittent intravenous infusion: 300 mg q 6 to 8 hours, infused over 15 to 20 minutes. In some patients it may be necessary to increase dosage. When this is necessary, the increases should be made by more frequent administration of a 300 mg dose, but should not exceed 2400 mg per day. Vials: Dilute Tagamet Injection, 300 mg, in at least 50 mL of 5% Dextrose Injection, or another compatible I.V. solution (see Stability of Tagamet Injection). Plastic containers: Use premixed Tagamet Injection, 300 mg, in 0.9% Sodium Chloride in 50 mL plastic containers. ADD-Vantage® Vials: Dilute contents of one vial in an ADD-Vantage® Diluent Container, available in 50 mL and 100 mL sizes of 0.9% Sodium Chloride Injection, and 5% Dextrose Injection.
Continuous intravenous infusion: 37.5 mg/hour (900 mg/day). For patients requiring a more rapid elevation of gastric pH, continuous infusion may be preceded by a 150 mg loading dose administered by I.V. infusion as described above. Dilute 900 mg Tagamet Injection in a compatible I.V. fluid (see Stability of Tagamet Injection) for constant rate infusion over a 24-hour period. Note: Tagamet may be diluted in 100 to 1000 mL; however, a volumetric pump is recommended if the volume for 24-hour infusion is less than 250 mL. In one study in patients with pathological hypersecretory states, the mean infused dose of cimetidine was 160 mg/hour with a range of 40 to 600 mg/hour.
These doses maintained the intragastric acid secretory rate at 10 mEq/hour or less. The infusion rate should be adjusted to individual patient requirements.
DIRECTIONS FOR USE OF TAGAMET (cimetidine hydrochloride) INJECTION IN PLASTIC CONTAINERS
To open: Tear overwrap down side at slit and remove solution containers.
Some opacity of the plastic due to moisture absorption during the sterilization process may be observed. This is normal and does not affect solution quality or safety. The opacity will diminish gradually.
Do not add other drugs to premixed Tagamet Injection in plastic containers.
CAUTION: Check for minute leaks by squeezing inner bag firmly. If leaks are found, discard solution as sterility may be impaired. Additives should not be introduced into this solution. Do not use if the solution is cloudy or precipitated or if the seal is not intact.
Do not use plastic containers in series connections. Such use could result in air embolism due to residual air being drawn from the primary container before administration of the fluid from the secondary container is complete.
Use sterile equipment.
PREPARATION FOR ADMINISTRATION:
Suspend container from eyelet support.
Remove plastic protector from outlet port at bottom of container.
Attach administration set. Refer to complete directions accompanying set.
DIRECTIONS FOR USE OF TAGAMET® INJECTION IN ADD-VANTAGE® VIALS are enclosed in ADD-Vantage® Vial packaging.
Stability of Tagamet Injection
When added to or diluted with most commonly used intravenous solutions, e.g., Sodium Chloride Injection (0.9%), Dextrose Injection (5% or 10%), Lactated Ringer's Solution, 5% Sodium Bicarbonate Injection, Tagamet (cimetidine hydrochloride) Injection should not be used after more than 48 hours of storage at room temperature.
Tagamet Injection premixed in plastic containers is stable through the labeled expiration date when stored under the recommended conditions.
DOSAGE ADJUSTMENT FOR PATIENTS WITH IMPAIRED RENAL FUNCTION
Patients with severely impaired renal function have been treated with Tagamet. However, such usage has been very limited. On the basis of this experience the recommended dosage is 300 mg q 12 hours orally or by intravenous injection. Should the patient's condition require, the frequency of dosing may be increased to q 8 hours or even further with caution. In severe renal failure, accumulation may occur and the lowest frequency of dosing compatible with an adequate patient response should be used. When liver impairment is also present, further reductions in dosage may be necessary. Hemodialysis reduces the level of circulating Tagamet. Ideally, the dosage schedule should be adjusted so that the timing of a scheduled dose coincides with the end of hemodialysis.
Patients with creatinine clearance less than 30 cc/min. who are being treated for prevention of upper gastrointestinal bleeding should receive half the recommended dose.