Quinine and carbenoxolone enhance the anticonvulsant activity of some classical antiepileptic drugs.

Objective Quinine (QUIN) and carbenoxolone (CNX) elicit anticonvulsant effects typically characterized by the reduction of the epileptiform activity as well as changes in behavioral parameters related to seizures. Therefore, the aim of this study was to analyze the effects of these molecules on the anticonvulsant activity of some classical antiepileptic drugs. Methods Male Wistar rats were used. Valproate (VPA), phenytoin (PHT), or carbamazepine (CBZ) was administered at sub-therapeutic doses for intraperitoneal via. Subsequently, animals were administered with a single dose of QUIN or CNX. The anticonvulsant activity was evaluated with the maximal electroshock (MES) test and pentylenetetrazole (PTZ) administration. Additionally, the plasma levels of CBZ were determined using an HPLC method. Results All the control rats presented generalized tonic-clonic seizures after the MES test or the administration of PTZ. For the MES test, all of the antiepileptic drugs increased their anticonvulsant activity when were co-administered with QUIN. For the PTZ test, only the combination CBZ plus QUIN significantly increased the percentage of protection against the generalized tonic-clonic seizures. The co-administration of CBZ plus QUIN resulted in an augmented concentration of CBZ in plasma. Discussion The present study shows that QUIN and CNX enhance the anticonvulsant activity of some classical antiepileptic drugs. However, only the combination CBZ/QUIN had significant effects on both MES and PTZ models. Such anticonvulsant activity could be attributed to increased levels of CBZ in plasma. We propose that these molecules could improve the pharmacological actions of antiepileptic drugs administered at sub-therapeutic doses.

Carbenoxolone treatment attenuates symptoms of metabolic syndrome and atherogenesis in obese, hyperlipidemic mice.

Glucocorticoids, which are well established to regulate body fat mass distribution, adipocyte lipolysis, hepatic gluconeogenesis, and hepatocyte VLDL secretion, are speculated to play a role in the pathology of metabolic syndrome. Recent focus has been on the activity of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which is capable of regenerating, and thus amplifying, glucocorticoids in key metabolic tissues such as liver and adipose tissue. To determine the effects of global 11beta-HSD1 inhibition on metabolic syndrome risk factors, we subcutaneously injected "Western"-type diet-fed hyperlipidemic mice displaying moderate or severe obesity [LDL receptor (LDLR)-deficient (LDLR(-/-)) mice and mice derived from heterozygous agouti (A(y)/a) and homozygous LDLR(-/-) breeding pairs (A(y)/a;LDLR(-/-) mice)] with the nonselective 11beta-HSD inhibitor carbenoxolone for 4 wk. Body composition throughout the study, end-point fasting plasma, and extent of hepatic steatosis and atherosclerosis were assessed. This route of treatment led to detection of high levels of carbenoxolone in liver and fat and resulted in decreased weight gain due to reduced body fat mass in both mouse models. However, only A(y)/a;LDLR(-/-) mice showed an effect of 11beta-HSD1 inhibition on fasting insulin and plasma lipids, coincident with a reduction in VLDL due to mildly increased VLDL clearance and dramatically decreased hepatic triglyceride production. A(y)/a;LDLR(-/-) mice also showed a greater effect of the drug on reducing atherosclerotic lesion formation. These findings indicate that subcutaneous injection of an 11beta-HSD1 inhibitor allows for the targeting of the enzyme in not only liver, but also adipose tissue, and attenuates many metabolic syndrome risk factors, with more pronounced effects in cases of severe obesity and hyperlipidemia.

Carbenoxolone does not cross the blood brain barrier: an HPLC study.

BACKGROUND: Carbenoxolone (CBX) is a widely used gap junctional blocker. Considering several reports indicating that transient gap junctional blockade could be a favourable intervention following injuries to central nervous tissue, and some current enthusiasm in studies using systemic injections of CBX, it is imperative to consider the penetration of CBX into central nervous tissue after systemic administrations. So far, only very indirect evidence suggests that CBX penetrates into the central nervous system after systemic administrations. We thus determined the amounts of CBX present in the blood and the cerebrospinal fluid of rats after intraperitoneal administration, using high performance liquid chromatography. RESULTS: CBX was found in the blood of the animals, up to 90 minutes post-injection. However, the cerebrospinal fluid concentration of CBX was negligible. CONCLUSION: Thus, we conclude that, most likely, CBX does not penetrate the blood brain barrier and therefore recommend careful consideration in the manner of administration, when a central effect is desired.

Corticosterone increases Na(+)-K(+)-ATPase activity in rat cortical collecting ducts with inhibition of 11 beta-hydroxysteroid dehydrogenase.

To examine a physiological role of 11 beta-hydroxysteroid dehydrogenase (11OHSD) in the aldosterone target tissue, we measured Na(+)-K(+)-ATPase activity in the cortical collecting ducts (CCD) from adrenalectomized rats, which were treated with a physiological dose of corticosterone and/or carbenoxolone (an inhibitor of 11OHSD). The Na(+)-K(+)-ATPase activity in adrenalectomized rats was not significantly changed by either corticosterone alone or carbenoxolone alone, whereas its activity showed a significant increase only in the rats that received both corticosterone and carbenoxolone. In these rats, the plasma concentration of corticosterone was within the physiological range (10(-6) M) and the plasma carbenoxolone concentration was about 10(-7) M. Furthermore, the direct effect of carbenoxolone was examined in the microdissected CCD because it has been reported that carbenoxolone per se had an affinity for the aldosterone receptor. Na+K(+)-ATPase activity in the microdissected CCD was increased in a dose-dependent manner after a 3-hour incubation with carbenoxolone, and this effect was completely inhibited by canrenoic acid (an aldosterone antagonist). However, the minimal carbenoxolone concentration exerting a stimulatory effect was 10(-6) M, which is about 10 times higher than the plasma concentration of carbenoxolone in the in vivo treated rats. These results indicate that an inhibition of 11OHSD but not a direct action of carbenoxolone induces an increase in Na(+)-K(+)-ATPase activity, which is a well-known aldosterone effect in the CCD.

Carbenoxolone interactions in man--preliminary report.

Carbenoxolone is a potent ulcer-healing drug which is extensively bound to plasma proteins and therefore has the potential for displacement interaction. However, carbenoxolone has been shown to be bound to human serum albumin in vitro at a different class of binding site to many other drugs and does not potentiate the pharmacological activity of warfarin, tolbutamide, chlorpropamide or phenytoin in the rat. In the present study four volunteers each received a single 100 mg dose of Biogastrone and the plasma half-life of carbenoxolone was determined. The procedure was repeated with a concurrent dose of either warfarin 10 mg, tolbutamide 500 mg, chlorpropamide 250 mg or phenytoin 100 mg. Chlorpropamide appeared to delay the absorption of carbenoxolone but no effects were observed with the other drugs. The study with concomitant chlorpropamide treatment was repeated with 6 gastric ulcer patients on an established Biogastrone regimen. In these patients the delayed absorption of carbenoxolone was confirmed although no changes in the glucose-lowering activity of chlorpropamide were evident. Further investigations into this findings are in progress.

Serum carbenoxolone: ulcer-healing and metabolic effects.

The relationship of serum carbenoxolone to dosage, age, sex, efficacy and side-effects were studied in 92 patients. Log serum carbenoxolone was correlated with dose and with age, and was higher in women. Serum levels were not significantly different in those patients with duodenal (or gastric) ulcer whose ulcers had or had not healed after allowance was made by analysis of variance for the effects of age and sex. However, oedema and hypokalaemia were associated with higher serum levels. These results support the concept that the ulcer-healing effect of carbenoxolone is topical rather than systemic.

Treatment of duodenal ulcer with carbenoxolone sodium: a double-masked endoscopic trial.

In a double-masked trial, 43 patients with an endoscopically confirmed, symptomatic duodenal ulcer were allocated at random to treatment with either carbenoxolone sodium or placebo, both provided in identical "positioned-release" capsules. The 40 patients who satisfactorily completed the trial were evenly distributed between the two treatment groups. The groups were well matched with regard to clinical features and initial ulcer size. Endoscopic review of ulcer healing after six weeks' treatment showed that 12 patients (60%) receiving carbenoxolone had healed ulcers, compared with five (25%) receiving placebo (P = 0.05). Symptomatic remission occurred by the fourth week in 17 patients (85%) receiving carbenoxolone, compared with six (30%) receiving placebo (P less than 0.001). The mean (geometric) serum carbenoxolone level in patients with healed ulcers was 31.11 microgram/mL compared with 17.75 microgram/mL in those with unhealed ulcers (P less than 0.005). Side effects of carbenoxolone therapy were observed, but they did not necessitate withdrawal of the drug and were readily controlled in every instance. These results confirm the therapeutic efficacy of carbenoxolone sodium in duodenal ulcer. In addition, a relationship between serum carbenoxolone levels and the occurrence of ulcer healing was observed.

Serum carbenoxolone in patients with gastric and duodenal ulcer: Absorption, efficacy and side-effects.

The absorption of carbenoxolone sodium has been studied in 15 patients with gastric ulcer and eight patients with duodenal ulcer treated for four weeks. Blood levels of carbenoxolone showed a log distribution, varied markedly between patients, and were significantly higher after Biogastrone tablets (300 mg/day) than after Duogastrone capsules (200 mg/day). Serum carbenoxolone levels were similar in patients taking Biogastrone tablets before or after meals, and in patients taking Biogastrone tablets or Duogastrone capsules with or without antacids following chronic administration. Serum carbenoxolone levels were similar in patients whose gastric ulcers had or had not healed after four weeks' treatment. Serum carbenoxolone was significantly higher in patients who developed oedema, and was significantly correlated with age and with fall in plasma potassium. Carbenoxolone may exert its metabolic effects systemically, but its ulcer-healing effects topically; additional studies are needed to test this hypothesis.

Controlled trial of a new dosage form of carbenoxolone (Pyrogastrone) in the treatment of reflux esophagitis.

A new preparation combining carbenoxolone sodium with alginate antacid (Pyrogastrone), taken for 8 weeks, was compared with alginate antacid alone (Gaviscon-like) in a controlled double-blind study in 37 patients with endoscopically proved reflux esophagitis. Complete remission or persistence of only minimal symptoms was obtained in 89%, and esophageal ulcer healing was achieved in 100% of subjects taking Pyrogastrone, compared with only 50% (P less than 0.025) and 33% (P equal 0.02), respectively, on control treatment. Complete endoscopic healing or persistence of only minimal inflammation was seen in 95% on Pyrogastrone and 67% of controls (P less than 0.05). Mild biochemical and clinical changes were noted in 9 of 19 patients on Pyrogastrone and 6 of 18 on the control drug, but none required treatment or alteration in regime. Thus Pyrogastrone is more effective in the treatment of reflux esophagitis than the most efficacious compound in current use.

Controlled trial of a carbenoxolone/alginate antacid combination in reflux oesophagitis.

A double-blind controlled trial was carried out in 37 patients with oesophagitis, confirmed endoscopically and histologically, to compare the efficacy of treatment with a carbenoxolone/alginate antaacid combination with that of the alginate antacid compound used alone. The total daily dosage of carbenoxolone was 100 mg. During the 8-week-period of the trial patients were seen every 2 weeks and endoscoped at 4 and 8 weeks. Response to treatment was assessed symptomatically and endoscopically using 6-point grading scales, and multiple oesophageal biopsies were taken at each endoscopy. The addition of carbenoxolone to the alginate antacid compound was shown to enhance symptomatic relief and to increase healing of oesophagitis and oesophageal ulceration significantly. No serious side-effects were reported in either group. Although there were a number of biochemical or clinical abnormalities recorded, none required any alteration in treatment.

Changes in the plasma clearance and protein binding of carbenoxolone with age, and their possible relationship with adverse drug effects.

Comparison by equilibrium dialysis of plasma protein binding sites for carbenoxolone in people under 40 years of age and in people over 65 years of age showed that the number of binding sites was reduced in the elderly and that this fall was associated with a reduction in plasma albumin levels. Although carbenoxolone has some aldosterone-like effects, these properties could not be shown to be due to displacement of aldosterone from its protein binding sites by competitive protein binding of carbenoxolone. Single doses of carbenoxolone were found to be removed considerably more slowly from the plasma of elderly individuals than from the young. The results of these three series of experiments suggest that the side-effects of carbenoxolone in the elderly may in part be caused by reduced protein binding, leaving more free drug in the active unbound form, and in part by reduced hepatic clearance mechanisms.

Controlled trial of Duogastrone in duodenal ulcer.

A double-blind placebo-controlled trial of carbenoxolone, as 50 mg Duogastrone capsules, and in a dose of 200 mg daily for 12 weeks, was carried out in 40 ambulant subjects with endoscopically diganosed duodenal ulceration, of whom 34 were available for final analysis. Each patient was seen every two weeks and endoscoped at four, eight and 12 weeks. Serum carbenoxolone was measured at each visit. Complete ulcer healing occurred in a significantly greater number of patients receiving Duogastrone than placebo, the significance being greater after four and eight weeks treatment (P less than 0-01) than at 12 weeks (P less than 0-02). While significant symptomatic improvement also was achieved (P less than 0-05), but only after 12 weeks on Duogastrone, there was much closer correlation between ulcer healing and symptom relief, 69% on Duogastrone returning to normal, compared with 22% of controls (P less than 0-02). Rise of systolic blood pressure and reduction in serum potassium levels, especially during the last four treatment weeks, were the most common effects noted in patients taking Duogastrone, and five patients required thiazide diuretics and potassium supplements. Higher serum carbenoxolone levels were found in patients with healed ulcers as well as in those with more marked side-effects.