PD-136,450: a CCK2 (gastrin) receptor antagonist with antisecretory, anxiolytic and antiulcer activity

Chemical constituents and medicinal properties of Allium species

Allium species, belonging to Alliaceae family, are among the oldest cultivated vegetables used as food. Garlic, onions, leeks and chives, which belong to this family, have been reported to have medicinal properties. The Allium species constituents have been shown to have antibacterial and antioxidant activities, and, in addition, other biological properties. These activities are related to their rich organosulfur compounds. These organosulfur compounds are believed to prevent the development of cancer, cardiovascular, neurological, diabetes, liver diseases as well as allergy and arthritis. There have also been reports on toxicities of these compounds. The major active compounds of Allium species includes, diallyl disulfide, diallyl trisulfide, diallyl sulfide, dipropyl disulfide, dipropyl trisulfide, 1-propenylpropyl disulfide, allyl methyl disulfide and dimethyl disulfide. The aim of this review is to focus on a variety of experimental and clinical reports on the effectiveness, toxicities and possible mechanisms of actions of the active compounds of garlic, onions, leek and chives.

Influence of the Novel Histamine H3 Receptor Antagonist/Inverse Agonist M39 on Gastroprotection and PGE2 Production Induced by (R)-Alpha-Methylhistamine in C57BL/6 Mice

The role of histamine H3 receptors (H3Rs) in the regulation of gastroprotection and production of prostaglandin E2 (PGE2) as well as somatostatin remains contradictory. Therefore, the effects of the H3R antagonist/inverse agonist M39 on in vivo acidified ethanol-induced gastric ulcers and gastric acid secretion in the C57BL/6 mice were assessed. Results showed that acute systemic administration of H3R agonist (R)-α-methylhistamine (RAMH, 100 mg/kg, i.g.) significantly reduced the severity of ulcer index, increased gastric acid output, and increased mucosal PGE2 production without any alteration of somatostatin concentration in gastric juice. However, only acute systemic administration of the H2R agonist dimaprit (DIM, 10 mg/kg, p.o.) significantly decreased the level of somatostatin measured in gastric juice. Moreover, acute systemic administration of M39 (0.3 mg/kg, i.g.) abrogated the RAMH-induced increase of acid output as well as PGE2 production, but not the DIM (10 mg/kg, i.g.)-stimulated acid secretion, indicating that RAMH as well as M39 modulate the gastroprotective effects through interactions with histamine H3Rs. The present findings indicate that agonistic interaction with H3Rs is profoundly involved in the maintenance of gastric mucosal integrity by modulating PGE2 as well as gastric acid secretion, with no apparent role in the regulation of the inhibitory influence of somatostatin.

Rabeprazole and Psychiatric Symptoms

Objective:

To report the case of a patient who developed marked anxiety associated with episodes of panic attacks after starting rabeprazole therapy.

Case Summary:

An otherwise healthy 55-year-old woman was prescribed rabeprazole 20 mg/day administered in the morning tor persistent symptoms of dyspepsia. Ten days later, she presented with a 7 day history of marked anxiety associated with panic attacks, night terror (pavor nocturnus), episodic mental confusion, and attention deficit. Within 2 days of discontinuing rabeprazole, the patient recovered completely from the neuropsychiatric manifestations. Subsequent esomeprazole therapy did not cause psychiatric symptoms.

Discussion:

Rabeprazole-induced hypergastrinemia may have played a role in this neuropsychiatric adverse reaction. Several lines of evidence have indicated that gastrin-releasing peptide, whose release is mediated by proton pump inhibitor (PPI)–induced secretion of gastrin, is involved in regulating aspects of behavior that might be altered in disorders such as anxiety, depression, and dementia. The fact that rabeprazole has the highest capacity of inducing gastrin increase compared with other PPIs might explain why our patient's panic symptoms disappeared after switching to esomeprazole. Based on the Naranjo probability scale, rabeprazole was the probable cause of the adverse reaction.

Conclusions:

Specific studies are needed to investigate the potential role of PPI-induced hypergastrinemia in neuropsychiatrie adverse reactions.

Novel approaches to the pharmacological blockade of gastric acid secretion

Research into new methods of controlling acid secretion is driven by existing medical needs in gastro-oesophageal reflux disease treatment. Histamine receptor subtype 3 agonists offer one approach for acid inhibition but no agent is yet undergoing clinical testing. Other, as yet unrealized strategies include preventing the fusion of the tubulovesicular elements that contain H+/K+-ATPase with the parietal cell membrane, or blocking channels that recycle K+ in the parietal cell. Of more promise are gastrin (cholecystokinin) receptor antagonists and potassium-competitive acid blockers; examples of both are in clinical development. It is probable that gastrin receptor antagonists would be used adjunctively with proton pump inhibitors, possibly for meal-induced reflux. The potassium-competitive acid blockers have attributes that may facilitate use as monotherapy for the treatment of gastro-oesophageal reflux disease. The early promise of gastrin receptor antagonists and potassium-competitive acid blockers remains to be defined in large-scale trials.