Prescribing information:
Famotidine
- Ulcer healing, by mouth: 40 mg at night.
- Maintenance dose, by mouth: 20 mg at night.
- Reflux oesophagitis, by mouth: 20“40 mg bd.
Nizatidine
- Ulcer healing, by mouth: 150 mg bd or 300 mg at night.
- Maintenance dose, by mouth: 150 mg at night.
- Reflux oesophagitis, by mouth: 150“300 mg bd.
- Also available in parenteral formulations (see note below).
Ranitidine
- Ulcer healing, by mouth: 150 mg bd or 300 mg at night.
- Maintenance dose, by mouth: 150 mg at night.
- Reflux oesophagitis: 150“300 mg bd.
- Also available in parenteral formulations (see note below).
- Parenteral use of these drugs is usually limited to prophylaxis against stress ulceration on the ICU.
- The usual dose of ranitidine for this indication is 50 mg tds; this should be reduced to 25 mg tds in severe renal insufficiency.
The principal effect of these drugs is inhibition of histamine-driven production of stomach acid. Gastric acid is produced through three major pathways (see teaching point below). One of these is stimulated by histamine. These drugs are effective antacid drugs but, because they act on only one of the pathways, they are not able to suppress gastric acid secretion completely, even at high dosages.
Drugs in this class
- Cimetidine
- Famotidine
- Nizatidine
- Ranitidine
- Ranitidine bismuth citrate
Safety
- Beware of prolonged treatment with these drugs without a diagnosis; they can mask the symptoms of gastric malignancy.
Efficacy
- Efficacy is usually judged by symptom relief.
- If ineffective reconsider the diagnosis.
- If the diagnosis is reflux oesophagitis, a proton pump inhibitor may be preferable.
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