In 'defence' of the gastric mucosa

Stimulation of duodenal bicarbonate secretion by carbenoxolone in rats: a comparative study with prostaglandin E2

1. The effects of carbenoxolone on duodenal HCO3- secretion were examined in anesthetized rats and compared with those of prostaglandin E2 (PGE2). 2. After 18-hr fasting, the duodenal loop (1.7 cm) that was made between the pyloric ring and the area just proximal to the outlet of the common bile duct was perfused with saline (pH 4.5), the pH of perfusate and the transmucosal potential difference (PD) were continuously monitored and HCO3- output was determined by titration with 10 mM HCl. 3. Under these conditions, duodenal pH, PD, and HCO3- secretion were increased in response to PGE2 (0.3 and 1.0 mg/kg) given intravenously as a single injection. Carbenoxolone (0.1-1.0 mg/kg, intravenously) also caused an increase in duodenal pH and HCO3- output in a dose-dependent manner, with a concomitant rise in PD; at 1 mg/kg, the magnitude of HCO3- output was almost equivalent to that induced by PGE2 at 0.3 mg/kg. 4. Prior administration of indomethacin, a cyclooxygenase inhibitor (5 mg/kg, subcutaneously), did not affect the HCO3- stimulatory action of carbenoxolone or PGE2. 5. Duodenal HCO3- secretion was also increased by intravenous injection of dibutylyl adenosine 3',5'-cyclic monophosphate (dbcAMP) but not by isobutylmethyl xanthine (IBMX; 10 mg/kg), an inhibitor of phosphodiesterase, but the former action was significantly potentiated in the presence of IBMX. Likewise, the pretreatment of IBMX significantly enhanced the HCO3- stimulatory action of PGE2 but had no effect on the HCO3- response induced by carbenoxolone. 6. These results suggest that carbenoxolone stimulates duodenal HCO3- secretion in rats, similar to PGE2 and this mechanism does not involve endogenous prostaglandins and is not associated with the intracellular accumulation of cAMP.

Gastric epithelial cell turnover, mucus production, and healing of gastric ulcers with carbenoxolone

Nineteen healthy subjects were studied and 17 patients with gastric ulcer before and after ulcer healing with carbenoxolone. Gastric deoxytibonucleic acid (DNA) loss was measured as an index of epithelial cell turnover, and N-acetylneuraminic acid (NANA) content of gastric juice as an index of mucus secretion. In normal subjects there was a negative correlation (p less that 0-025) between gastric DNA loss and NANA secretion; the lower the cell turnover the higher the NANA production. In gastric ulcer patients DNA loss or turnover was significantly (p less than 0-01) higher than normal, and fell significantly (p less than 0-01) after four weeks' treatment with carbenoxolone when 16 of the 17 ulcers had healed. At the same time NANA output increased significantly (p less than 0-01). It is suggested that patients with gastric ulcer lose cells at a high rate, a state of affairs which is returned towards normal by carbenoxolone, thus allowing the epithelial cells to mature within the mucosa and produce more mucus.

Carbenoxolone sodium: its role in ulcer healing

In summary, carbenoxolone is a useful drug in accelerating short-term ulcer healing during ambulatory treatments. Provided treatment is responsibly controlled the adverse effects should not present frequent or severe problems; however, there is a clear need for an analogue which is substantially side-effect free.

Carbenoxolone: a review of its pharmacological properties and therapeutic efficacy in peptic ulcer disease

Carbenoxolone sodium has been shown to accelerate the rate of healing of both gastric and duodenal ulcers, but its overall value in duodenal ulcer is probably less because of the high rate of natural remission of duodenal ulcers. Further studies are required to decide whether it should be used prophylactically to delay ulcer recurrence. Carbenoxolone may act by affecting both the proliferative activity of gastric epithelium and the differentiation of the epithelial cells to produce mucus (as well as favourably altering the physicochemical properties of mucus and by reducing peptic activity), factors which may be relevant ot the prevention of acute gastric ulcers. Some studies suggest that carbenoxolone adds to the effect of hospitalisation and bed rest on ulcer healing. Whether bed rest confers additional benefit to the drug's ulcer healing effect in outpatients is also uncertain. There is no evidence that accelerated healing by carbenoxolone is associated with improved overall prognosis. Carbenoxolone is of greatest benefit in accelerating the healing of gastric ulcers in patients for whom hospitalisation is not possible or desirable, but it should only be used in the ambulatory patient when careful and regular observation of serum electrolytes (particularly potassium), blood pressure and weight is possible and when it is known that the patient will attend regular follow-up. Patient must be educated in the proper use of the drug. If severe mineralocorticoid-like toxic effects such as sodium and water retention and hypokalaemia appear, as they do in a variable proportion of patients but most frequently in those receiving excessive doses, carbenoxolone should be stopped and the complication treated; they respond to thiazide diuretics and potassium supplements, and probably to amiloride given in conjunction with a low dose of a thiazide diuretic. Treatment with carbenoxolone can continue with concurrent diuretic therapy in patients with less severe side-effects. Optimum therapeutic effect in gastric ulcer with the least side-effects is achieved with a dosage of 100mg carbenoxolone tablets 3 times daily for the first week followed by 50mg 3 times daily thereafter, best taken before meals. A lower dosage is desirable in the elderly and in those with liver, cardiac or renal disease. Barium meal or preferably endoscopic examinations should be performed regularly and therapy continued until the ulcer is healed. Dosage for duodenal ulcer is 50mg 4 times daily, in special positioned-release capsules. These are best taken about 20 minutes before meals.