Circulating cyclic nucleotides and amines in human cholera

Effects of histamine and 5-hydroxytryptamine on the growth rate of xenografted human bronchogenic carcinomas

1. The influence of histamine and 5-hydroxytryptamine (5-HT) antagonists and agonists on the volume doubling times (Td) of human bronchogenic carcinomas propagated as s.c. xenografts in immunosuppressed mice was examined. 2. The H2-receptor antagonists, cimetidine and ranitidine, increased Td. 3. Treatment with the H2-receptor agonist, 4-methyl histamine, had no effect on Td. 4. Co-administration of 4-methyl histamine and cimetidine abolished the effects of cimetidine. 5. The 5-HT2-receptor antagonists, cinanserin and ketanserin, both increased Td. 6. Treatment with the 5-HT1/2-receptor agonist quipazine (0.1 mg/kg, reflecting 5-HT2 agonist activity) decreased Td, while a higher dose (10.0 mg/kg) had no effect. 7. The 5-HT1/2-receptor antagonist, methiothepin, decreased Td. 8. The 5-HT uptake inhibitor, fluoxetine, increased Td in one tumour line but not in another, while the 5-HT releaser/depletor, fenfluramine, increased Td. 9. Histamine may stimulate tumour growth through the histamine H2-receptor, while the dominant effect of 5-HT is 5-HT1-receptor inhibition. 10. Tumour growth in some bronchogenic carcinomas may involve 5-HT uptake mechanisms.

Ranitidine hydrochloride

Ranitidine is a selective, competitive histamine H2-receptor antagonist recently approved by the Food and Drug Administration for use in the short-term treatment of active duodenal ulcers and gastric hypersecretory conditions. Ranitidine is four to ten times more potent than cimetidine on a molar basis in inhibiting stimulated gastric acid secretion. Clinical studies have demonstrated that ranitidine is as effective as cimetidine and is similarly well tolerated. Based on available literature (approximately 700 publications), this article reviews the pharmacology, safety profile, and clinical efficacy of ranitidine in duodenal ulcers and gastric hypersecretory conditions.