Gastric origin of the first-pass metabolism of ethanol in humans: effect of gastrectomy

Gastric ethanol metabolism and gastritis: interactions with other drugs, Helicobacter pylori, and antibiotic therapy (1957-1997)--a review

The stomach provides some protection against the penetration of ethanol into the body by contributing to the metabolism of ethanol. The latter is attenuated by various drugs and, although the magnitude of this effect is still the subject of debate, patients should be warned of the corresponding possible increase in blood alcohol levels. Furthermore, oxidation of ethanol generates acetaldehyde, a toxic metabolite. In addition, chronic alcohol abuse seems to favor colonization by Helicobacter pylori, which produces ammonia that also contributes to the commonly associated chronic gastritis. Because antibiotics were shown over the last 4 decades to effectively eliminate gastric ammonia, they should be considered for the routine treatment of such chronic gastritis in the way they are now being used for ulcer therapy.

Pharmacokinetic interactions between alcohol and other drugs

The frequent use of alcohol (ethanol) together with prescription drugs gives any described pharmacokinetic interaction significant clinical implications. The issue is both the effect of alcohol on the pharmacokinetics of various drugs and also the effect of those drugs on the pharmacokinetics of alcohol. This review discusses these pharmacokinetic interactions but also briefly describes some other effects of alcohol that are clinically relevant to drug prescribing. The use of several different study designs may be required before we can confidently state the presence or absence of any alcohol-drug interaction. Short term administration of alcohol in volunteers is the most common study design but studies of social drinking and prolonged moderate alcohol intake can be important in some situations. Community-based studies may illustrate the clinical relevance of any interaction. Alcohol can affect the pharmacokinetics of drugs by altering gastric emptying or liver metabolism (by inducing cytochrome P450 2E1). Drugs may affect the pharmacokinetics of alcohol by altering gastric emptying and inhibiting gastric alcohol dehydrogenase. The role of gastric alcohol dehydrogenase in the first-pass metabolism of alcohol is reviewed in this article and the arguments for and against any potential interaction between alcohol and H2 receptor antagonists are also discussed. The inhibition of the metabolism of acetaldehyde may cause disulfiram-like reactions. Pharmacodynamic interactions between alcohol and prescription drugs are common, particularly the additive sedative effects with benzodiazepines and also with some of the antihistamine drugs; other interactions may occur with tricyclic antidepressants. Alcohol intake may be a contributing factor to the disease state which is being treated and may complicate treatment because of various pathophysiological effects (e.g. impairment of gluconeogenesis and the risk of hypoglycaemia with oral hypoglycaemic agents). The combination of nonsteroidal anti-inflammatory drugs and alcohol intake increases the risk of gastrointestinal haemorrhage.

First-pass metabolism of ethanol is negligible in rat gastric mucosa

Controversy exists concerning whether first-pass metabolism of imbibed ethanol occurs in the gastric mucosa or liver. We assessed ethanol metabolism in rat gastric mucosa by determining to what extent intact [14C]ethanol in body water plus hepatic metabolism could account for [14C]ethanol absorbed from the pylorus-ligated stomach. Intact [14C]ethanol in systemic body water accounted for 84 +/- 1.9% of the [14C]ethanol absorbed from the stomach over a 30-min period. Assuming a 15 ml/min hepatic blood flow, the predicted hepatic metabolism of [14C]ethanol over the 30 min of the study was 18% of the dose. The sum of intact [14C]ethanol and predicted hepatic metabolism accounted for 100% of the ethanol absorbed from the stomach. We conclude that negligible metabolism of ethanol occurred in the gastric mucosa.

The effect of cimetidine on ethanol concentrations in fasting women and men after two different doses of alcohol

BACKGROUND

Serum ethanol concentrations may become higher when alcohol is consumed during treatment with histamine receptor antagonists, especially if ethanol is ingested postprandially. Only a few studies have investigated fasting subjects, and women have only been investigated sporadically.

METHODS

The present study compared serum ethanol concentrations after a 4-h fast followed by a low (0.15 g/kg) and a high (0.45 g/kg) dose of ethanol, on two separate occasions in six women and six men. The study was carried out before and after treatment with 400 mg cimetidine twice daily.

RESULTS

Cimetidine administration did not change the area under the concentration-time curve or the maximal serum ethanol concentration in either women or men, irrespective of ethanol dose. Ethanol elimination rate was unchanged by cimetidine.

CONCLUSION

Cimetidine does not influence the ethanol concentration-time curve when ethanol is ingested on an empty stomach.

Ethanol metabolism, cirrhosis and alcoholism

Alcohol-induced tissue damage results from associated nutritional deficiencies as well as some direct toxic effects, which have now been linked to the metabolism of ethanol. The main pathway involves liver alcohol dehydrogenase which catalyzes the oxidation of ethanol to acetaldehyde, with a shift to a more reduced state, and results in metabolic disturbances, such as hyperlactacidemia, acidosis, hyperglycemia, hyperuricemia and fatty liver. More severe toxic manifestations are produced by an accessory pathway, the microsomal ethanol oxidizing system involving an ethanol-inducible cytochrome P450 (2E1). After chronic ethanol consumption, there is a 4- to 10-fold induction of 2E1, associated not only with increased acetaldehyde generation but also with production of oxygen radicals that promote lipid peroxidation. Most importantly, 2E1 activates many xenobiotics to toxic metabolites. These include solvents commonly used in industry, anaesthetic agents, medications such as isoniazid, over the counter analgesics (acetaminophen), illicit drugs (cocaine), chemical carcinogens, and even vitamin A and its precursor beta-carotene. Furthermore, enhanced microsomal degradation of retinoids (together with increased hepatic mobilization) promotes their depletion and associated pathology. Induction of 2E1 also yields increased acetaldehyde generation, with formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, impaired utilization of oxygen, glutathione depletion, free radical-mediated toxicity, lipid peroxidation, and increased collagen synthesis. New therapies include adenosyl-L-methionine which, in baboons, replenishes glutathione, and attenuates mitochondrial lesions. In addition, polyenylphosphatidylcholine (PPC) fully prevents ethanol-induced septal fibrosis and cirrhosis, opposes ethanol-induced hepatic phospholipid depletion, decreased phosphatidylethanolamine methyltransferase activity and activation of hepatic lipocytes, whereas its dilinoleoyl species increases collagenase activity. Current clinical trials with PPC are targeted on susceptible populations, namely heavy drinkers at precirrhotic stages.

Ethnic differences in gastric sigma-alcohol dehydrogenase activity and ethanol first-pass metabolism

We assessed whether the low sigma-alcohol dehydrogenase (ADH) activity in Japanese (compared with Caucasians) affects the first-pass metabolism of ethanol. ADH isozyme activities were determined in endoscopic biopsies of the gastric corpus from 24 Japanese and 41 Caucasian men by starch gel electrophoresis and by comparing the reduction of m-nitrobenzaldehyde (a preferred substrate of sigma-ADH) with that of acetaldehyde (a preferred substrate of gamma-ADH) and the glutathione-dependent formaldehyde oxidation (a specific reaction of chi-ADH). Alcohol pharmacokinetics was compared in 10 Japanese and 10 Caucasians after administration of ethanol (300 mg/kg of body weight) intravenously or orally, using 5 and 40% oral solutions. Japanese exhibited lower sigma-ADH activity than Caucasians, with no difference in the other gastric isozymes. With 5% ethanol, first-pass metabolism was strikingly lower in Japanese than in Caucasians. Blood alcohol levels were similar because of the high elimination rate in Japanese due to the hepatic beta 2-ADH variant. With 40% ethanol, the first-pass metabolism increased in both groups to comparable levels, suggesting an additional contribution by chi-ADH at high ethanol concentrations. These results indicate that sigma-ADH activity contributes significantly to gastric ethanol oxidation and its lower activity in Japanese is associated with lesser first-pass metabolism.

Role of catalase in rat gastric mucosal ethanol metabolism in vitro

To evaluate the possible role of catalase in gastric ethanol metabolism in rats, we studied acetaldehyde formation from ethanol by gastric mucosal homogenate under various in vitro conditions. Homogenized rat gastric mucosa produced significant amounts of acetaldehyde in a time and ethanol concentration-dependent manner, even in the absence of added NAD. Both acetaldehyde formation and catalase activity peaked around the physiological pH, whereas alcohol dehydrogenase (ADH) activity was in that pH range low and reached peak values only at a higher pH of 9 to 10. Catalase inhibitors sodium azide (SA) and 3-amino-1,2,4-triazole (3-AT) had little effect on ADH activity but markedly decreased catalase activity and acetaldehyde formation (1 mM of SA to 56 +/- 13% of control, 5 mM of 3-AT to 67 +/- 3% of control; mean +/- SE). 4-Methylpyrazole decreased ADH activity significantly, but did not affect acetaldehyde formation. Heating of the homogenate at 60 degrees C for 5 min decreased ADH activity only slightly, but totally abolished catalase activity and reduced acetaldehyde formation to 39 +/- 3% of control. Addition of a H2O2 generating system (beta-D(+)-glucose + glucose oxidase] increased acetaldehyde formation in a concentration-dependent manner up to 8-fold of the control value. Our results strongly suggest that, in addition to ADH, catalase may play a significant role in gastric ethanol metabolism in rats.

Gastric emptying and first-pass metabolism of ethanol in elderly subjects with and without atrophic gastritis

BACKGROUND

Oral ethanol intake results in lower blood ethanol concentrations than intravenous administration of the same dose of ethanol. This first-pass metabolism is thought to be due to gastric metabolism of ethanol via alcohol dehydrogenase and also to hepatic first-pass metabolism.

METHODS

Since a loss of gastric mucosa may decrease first-pass metabolism of ethanol, this metabolism was studied in 10 elderly subjects (6 women and 4 men) with atrophic gastritis and bacterial overgrowth and in 17 control subjects with normal gastric secretory function. Atrophic gastritis was verified by means of the serum pepsinogen I to pepsinogen II ratio and the hypochlorhydria occurring after pentagastrin stimulation. Bacterial overgrowth was assessed by bacteria. In addition, gastric emptying rates of ethanol solution with technetium-99m sulfur colloid were calculated from scintigraphic images. Furthermore, gastric biopsy specimens were taken from 12 female patients with atrophic gastritis and from 12 controls for determination of alcohol dehydrogenase activity.

RESULTS

Neither gender (female versus male, 28 +/- 5% versus 42 +/- 5%), atrophic gastritis (normal versus atrophic gastritis, 35 +/- 4% versus 32 +/- 6%), nor tetracycline treatment in atrophic gastritis subjects (before versus after, 32 +/- 6% versus 41 +/- 5%) had a statistically significant effect on the first-pass metabolism of ethanol in the elderly. Gastric alcohol dehydrogenase activity was significantly lower in atrophic gastritis subjects than in controls (p < 0.01). A significant correlation was found between the first-pass metabolism of ethanol in healthy controls and gastric half-emptying time (p = 0.032).

CONCLUSIONS

We conclude from these data that the rate of gastric emptying modulates first-pass metabolism of ethanol in elderly individuals.

Disposition and first-pass metabolism of ethanol in humans: is it gastric or hepatic and does it depend on gender?

OBJECTIVE

To assess the extent and site of the first-pass metabolism of ethanol and to examine whether first-pass metabolism and disposition of ethanol are dependent on gender.

METHODS

After a standardized lunch, healthy subjects (six women and six men) received on two separate occasions a 60-minute intravenous infusion of ethanol (0.3 gm/kg) and concomitantly an equimolar dose of d3-ethanol/kg either orally (over 20 minutes) or intraduodenally (infused over 30 minutes). Blood levels, urinary excretion of d0- and d3-ethanol, and sedative effects were monitored for 6 hours. Disposition and first-pass metabolism of ethanol were evaluated by applying an open two-compartment model with Michaelis-Menten elimination.

RESULTS

Comparison of the corresponding intravenous/oral versus intravenous/intraduodenal data of each individual revealed that total first-pass metabolism (gastric plus hepatic) was not pronounced in either males (9.1% +/- 4.0%; mean +/- SD) or females (8.4% +/- 3.1%) and that this first-pass metabolism was partly of gastric origin. Dose-corrected values for area under blood concentration-time curve were on average 28% higher (p < 0.0001) in the women than in the men. Mean total blood ethanol disappearance rate was higher (p < 0.001) in women (3.92 +/- 0.40 mmol/L . hr) than in men (3.19 +/- 0.48 mmol/L . hr). Renal clearance was gender-independent and negligible. A linear relationship (p < 0.001) could be found between the blood levels of ethanol and sedation index. Because the slope was steeper in women (1.04) than in men (0.42) a higher central nervous system sensitivity to the sedative effects of ethanol in women can be assumed.

CONCLUSIONS

Under realistic life conditions (social drinking of moderate doses of ethanol after a light lunch) only a minor, gender-independent first-pass metabolism is observed that is partly of gastric origin.

Aldehyde dehydrogenases of the rat colon: comparison with other tissues of the alimentary tract and the liver

Intracolonic bacteria have previously been shown to produce substantial amounts of acetaldehyde during ethanol oxidation, and it has been suggested that this acetaldehyde might be associated with alcohol-related colonic disorders, as well as other alcohol-induced organ injuries. The capacity of colonic mucosa to remove this bacterial acetaldehyde by aldehyde dehydrogenase (ALDH) is, however, poorly known. We therefore measured ALDH activities and determined ALDH isoenzyme profiles from different subcellular fractions of rat colonic mucosa. For comparison, hepatic, gastric, and small intestinal samples were studied similarly. Alcohol dehydrogenase (ADH) activities were also measured from all of these tissues. Rat colonic mucosa was found to possess detectable amounts of ALDH activity with both micromolar and millimolar acetaldehyde concentrations and in all subcellular fractions. The ALDH activities of colonic mucosa were, however, generally low when compared with the liver and stomach, and they also tended to be lower than in small intestine. Mitochondrial low K(m) ALDH2 and cytosolic ALDH with low K(m) for acetaldehyde were expressed in the colonic mucosa, whereas some cytosolic high K(m) isoenzymes found in the small intestine and stomach were not detectable in colonic samples. Cytosolic ADH activity corresponded well to ALDH activity in different tissues: in colonic mucosa, it was approximately 6 times lower than in the liver and about one-half of gastric ADH activity. ALDH activity of the colonic mucosa should, thus, be sufficient for the removal of acetaldehyde produced by colonic mucosal ADH during ethanol oxidation. It may, however, be insufficient for the removal of the acetaldehyde produced by intracolonic bacteria. This may lead to the accumulation of acetaldehyde in the colon and colonic mucosa after ingestion of ethanol that might, at least after chronic heavy alcohol consumption, contribute to the development of alcohol-related colonic morbidity, diarrhea, and cancer.

Alcohol dehydrogenase (ADH) isozymes in the AdhN/AdhN strain of Peromyscus maniculatus (ADH-deermouse) and a possible role of class III ADH in alcohol metabolism

Although the AdhN/AdhN strain of Peromyscus maniculatus (so-called ADH- deermouse) has been previously considered to be deficient in ADH, we found ADH isozymes of Classes II and III but not Class I in the liver of this strain. On the other hand, the AdhF/AdhF strain (so-called ADH+ deermouse), which has liver ADH activity, had Class I and III but not Class II ADH in the liver. In the stomach, Class III and IV ADHs were detected in both deermouse strains, as well as in the ddY mouse, which has the normal mammalian ADH system with four classes of ADH. These ADH isozymes were identified as electrophoretic phenotypes on the basis of their substrate specificity, pyrazole sensitivity, and immunoreactivity. Liver ADH activity of the ADH- strain was barely detectable in a conventional ADH assay using 15 mM ethanol as substrate; however, it increased markedly with high concentrations of ethanol (up to 3 M) or hexenol (7 mM). Furthermore, in a hydrophobic reaction medium containing 1.0 M t-butanol, liver ADH activity of this strain at low concentrations of ethanol (< 100 mM) greatly increased (about sevenfold), to more than 50% that of ADH+ deermouse. These results were attributable to the presence of Class III ADH and the absence of Class I ADH in the liver of ADH- deermouse. It was also found that even the ADH+ strain has low liver ADH activity (< 40% that of the ddY mouse) with 15 mM ethanol as substrate, probably due to low activity in Class I ADH. Consequently, liver ADH activity of this strain was lower than its stomach ADH activity, in contrast with the ddY mouse, whose ADH activity was much higher in the liver than in the stomach, as well as other mammals. Thus, the ADH systems in both ADH- and ADH+ deermouse were different not only from each other but also from that in the ddY mouse; the ADH- strain was deficient in only Class I ADH, and the ADH+ strain was deficient in Class II ADH and down-regulated in Class I ADH activity. Therefore, Class III ADH, which was found in both strains and activated allosterically, may participate in alcohol metabolism in deermouse, especially in the ADH- strain.

First-pass metabolism of alcohol. Absence of diurnal variation and its inhibition by cimetidine after evening meal

To determine whether the first-pass metabolism (FPM) of orally consumed alcohol varies with the time of day, 12 healthy male subjects were tested with both oral and intravenous alcohol (0.3 g/kg), in the morning and evening, always 1 hr after the same standard meal. The results revealed no significant differences in FPM (81.6 +/- 11.6 vs 92.8 +/- 10.6 mg/kg) or in any other index of alcohol absorption and metabolism. Eleven subjects were also tested in the evening after treatment with cimetidine, an H2-antagonist that inhibits gastric alcohol dehydrogenase activity in vitro. Compared to baseline, cimetidine (1 g/day for eight days) significantly decreased FPM (from 100.1 +/- 8.0 to 52.6 +/- 11.4 mg/kg, P < 0.01) and increased the systemic bioavailability of alcohol (from 66 +/- 3 to 82 +/- 4%, P < 0.01), as well as peak blood alcohol concentrations (from 4.3 +/- 0.4 to 5.9 +/- 0.5 mM, P < 0.05) and areas under the curve (from 5.1 +/- 0.5 to 7.0 +/- 0.5 mM/hr, P < 0.01). The results indicate the absence of diurnal variation in FPM and suggest that patients given cimetidine should be warned of its possible interaction with alcohol regardless of the time of day.

Inter-individual and intra-individual variability of ethanol concentration-time profiles: comparison of ethanol ingestion before or after an evening meal

1. The magnitude of the variability of ethanol absorption is an important factor for studies that seek to determine the significance of potential interactions between ethanol and drugs. The aim of this study was to determine the extent of inter- and intra-individual variability of ethanol concentration-time profiles in fasted and fed subjects. 2. Twenty-four healthy male subjects were randomized to receive ethanol 0.3 g kg-1 before an evening meal on two study days and ethanol 0.3 g kg-1 after an evening meal on two study days. Plasma ethanol concentrations were measured at intervals from 0-240 min. 3. There were significant differences in the mean area under the ethanol concentration-time curve (AUC), the mean peak ethanol concentration (Cmax), the mean ethanol elimination slope and the time to peak ethanol concentration between the fed and fasted subjects. There were no significant differences between the first and second study days for either fed or fasting subjects for all parameters. 4. There was no statistically significant difference in inter- or intra-subject variance between fed and fasted studies although the coefficients of variation (standard deviation expressed as a percentage of the mean) for the differences between the first and second study day were higher for fed studies. 5. The large inter- and intra-individual variability of alcohol absorption for both fasted and fed subjects must be considered in the design of alcohol-drug interaction studies.

Gastrectomy enhances vulnerability to the development of alcoholism

A history of gastrectomy was more frequently encountered in Japanese male alcoholics (9.7%, 47/486) than in male employee populations of two large companies (0.8%, 36/4,381, p < 0.001, and 0.6%, 6/950, p < 0.001). Gastrectomized men are known to achieve a higher blood ethanol level after the ingestion of the equal amount of ethanol than nongastrectomized men. To examine whether or not gastrectomy was responsible for the subsequent development of alcohol dependence, 47 gastrectomized alcoholics were compared with 47 age-matched nongastrectomized alcoholics. The mean lifetime duration of heavy drinking (> 120 g ethanol/day) was shorter in the former than in the latter (11 +/- 10 years vs. 16 +/- 9, p < 0.05), and the mean lifetime cumulative ethanol consumption level also smaller (834 +/- 497 kg vs. 1047 +/- 508, p < 0.05). The majority of gastrectomized patients (30/47) had no history of problem drinking before gastrectomy. The daily consumption was rapidly increased within 5 years after gastrectomy in 18 of 38 habitual drinkers (47%). Seven of the remaining nine nonhabitual drinkers (78%) became habitual drinkers and alcoholics within a short period of time (7 +/- 4 years), though with low lifetime cumulative consumption (< 400 kg). The incidence of disorders of the central and peripheral nervous systems observed did not differ between the two groups, except for frequent alcoholic blackouts reported in the gastrectomized patients. In conclusion, the majority of the gastrectomized patients changed their drinking habits after gastrectomy and developed alcohol dependence. They did not require as much lifetime cumulative ethanol as nongastrectomized patients to become ethanol dependent.

Metabolism of ethanol in rat gastric cells and its inhibition by cimetidine

BACKGROUND/AIMS

Several studies have shown that the stomach has sufficient alcohol dehydrogenase activity to metabolize a significant amount of alcohol and that cimetidine depresses this alcohol dehydrogenase activity. However, both gastric metabolism of ethanol and its inhibition by cimetidine remain controversial. Given the difficulty in assessing gastric metabolism of ethanol in vivo, this subject was investigated in vitro.

METHODS

Cultured rat gastric epithelial cells were incubated with 200 mmol/L [1-14C]ethanol for 90 minutes with and without cimetidine (0.1-1 mmol/L) or omeprazole (1 mmol/L). The quantity of ethanol oxidized by gastric cells was measured by the amount of acetate produced using ion exchange chromatography.

RESULTS

The majority of cells at confluency had typical features of mucous cells. The gastric cells metabolized significant amounts of ethanol, sufficient to account for in vivo first-pass metabolism of ethanol in rats. Cimetidine, but not omeprazole, reduced ethanol metabolism by 39.9% +/- 4.9% (P < 0.01), an inhibition comparable with that previously reported for first-pass metabolism in vivo.

CONCLUSIONS

Gastric cells in tissue culture are capable of significant ethanol oxidation, the in vitro rates are sufficient to account for first-pass metabolism of ethanol in vivo, and cimetidine inhibits ethanol metabolism in tissue culture, an effect that parallels its decrease of first-pass metabolism in vivo.

Prolonged consumption of moderate doses of alcohol and in vitro gastro-duodenal and ileal contractility in the rat

The effects of chronic feeding with moderate doses of ethanol (3% vol/vol in drinking water for 8 weeks), which do not induce tolerance, dependence and withdrawal, on the contractility of gastric, duodenal and ileal strips from rats were investigated. Only 50% of ethanol-treated specimens (as compared to 100% of saccharose-fed controls) exhibited antral phasic contractions (frequency decreased by 31% and 27% in the antrum and duodenum, respectively; P < 0.03 vs. controls). The depolarizing agent potassium chloride (KCl, 80 mM) produced less peak active tension in the fundus of ethanol-fed rats (P < 0.01). In alcoholic rats the sensitivity of the antrum to acetylcholine was fourfold less than that of control specimens. It is concluded that, in the rat, moderate doses of ethanol given chronically impair both spontaneous and tonic contractility of the stomach and duodenal muscle without affecting ileal contraction. It is possible that motility defects in the gut exposed to ethanol concentrations which do not cause tolerance, dependence or withdrawal in the rat may be due to a local rather than a systemic effect on the smooth muscle.

Molecular biological aspects of alcohol-induced liver disease

Molecular biological investigations have become a predominant methodology applied to the study of alcohol-induced liver disease. The enzymatic pathways responsible for ethanol metabolism, and their genetic as well as environmental control, have become the focus of detailed investigation. More recently, the significance of cytokines in the pathogenesis of alcohol-induced liver disease has also become a major area of speculation. This review focuses on the advances made in studies of two important enzymes responsible for alcohol metabolism, alcohol dehydrogenase and aldehyde dehydrogenase, as well as the investigation of the proinflammatory and profibrogenic cytokines involved in the process of hepatic fibrogenesis. The quality and quantity of new discoveries made in the field of alcohol-induced liver disease is impressive, especially when one realizes that molecular biological approaches have been employed in this area for only 15 years. However, in most cases the studies have been predominantly descriptive, with little direct relevance to the therapeutics of alcoholism and alcohol-induced organ injury. Because the groundwork has been laid, one hopes that the next 15 years will rectify this failure.

Hepatic and metabolic effects of ethanol: pathogenesis and prevention

Mechanisms of the hepatotoxicity of ethanol are reviewed, including effects resulting from alcohol dehydrogenase (ADH) mediated excessive hepatic generation of NADH and acetaldehyde. Gastric ADH explains first-pass metabolism by ethanol; its activity is low in alcoholics and in females and is decreased by some commonly used drugs. In addition to ADH, ethanol can be oxidized by liver microsomes: studies over the last 25 years have culiminated in the molecular elucidation of the ethanol-inducible cytochrome P-450 (2E1) which causes metabolic tolerance to ethanol and to various commonly used medications, enhanced degradation of testosterone and vitamin A (with vitamin A depletion) and selective hepatic perivenular toxicity. The latter results from free radical generation and activation of various xenobiotics, causing increased vulnerability of the heavy drinker to the toxicity of industrial solvents, anaesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens and even nutritional factors such as vitamin A and beta-carotene. Furthermore, induction of the microsomal pathway contributes to increased acetaldehyde generation which promotes GSH depletion and lipid peroxidation and other toxic effects. Nutritional deficits may affect the toxicity of ethanol and acetaldehyde, as illustrated by the depletion in glutathione, ameliorated by S-adenosyl-L-methionine. Other 'supernutrients' include polyenylphosphatidylcholine, shown to correct the alcohol-induced hepatic phosphatidylcholine depletion and to prevent alcoholic cirrhosis in non-human primates.

Bioavailability of ethanol is reduced in several commonly used liquid diets

Liquid diets are often used as a vehicle for chronically treating laboratory animals with ethanol. However, a recent report suggested that one or more components of these diets may bind ethanol which could result in a decrease in the bioavailability of ethanol. Consequently, we compared the blood ethanol concentration vs. time curves obtained following the intragastric (i.g.) administration of ethanol dissolved in water or in one of three liquid diets (Bioserv AIN-76, Sustacal, or Carnation Slender) using the long-sleep (LS) and short-sleep (SS) mouse lines. The initial rates of absorption were generally the same for the water-ethanol and diet-ethanol groups, but the diets generally produced lower peak levels and the areas under the ethanol concentration-time curves were less for all of the liquid diets than for the control, ethanol-water solution. In vitro dialysis experiments indicated that the Bioserv diet binds ethanol in a saturable manner. Therefore, it may be that the slower release of ethanol, which should occur as a result of binding, serves to increase the role of first pass metabolism in regulating ethanol concentrations following oral administration. Because the effects of the diets were seen even after pyrazole treatment, it may be that the lower blood ethanol levels arise because metabolism by gastric ADH, rather than hepatic ADH, is responsible for a major portion of ethanol metabolism as ethanol is slowly released by the diets. If so, the observation that the diet/water differences were uniformly greater in the LS mice may indicate that LS-SS differences in gastric ADH exist.(ABSTRACT TRUNCATED AT 250 WORDS)

H2-antagonists and alcohol. Do they interact?

There are conflicting data on the existence of significant first-pass metabolism of alcohol (ethanol) in the human stomach and its inhibition by histamine H2-receptor antagonists. Alcohol is predominantly metabolised in the liver by the microsomal alcohol oxidising system, alcohol dehydrogenase (ADH) and a catalase enzyme. Histochemical and kinetic studies have revealed several ADH isoenzymes in the gastric mucosa with different kinetic properties. After small oral doses of alcohol first-pass metabolism in the stomach occurs, as shown by reduced area under the plasma concentration-time curve (AUC) compared with intravenous or intraduodenal administration. The activity of gastric ADH is reduced in women, the elderly, Asian individuals, the fasting state, chronic alcoholism and after gastrectomy. The effect is only present with small (< or = 0.3 g/kg) alcohol doses and with a high alcohol concentration. In a number of studies, cimetidine in therapeutic doses over 7 days produced a significant increase in the AUC and in the peak plasma concentration after administration of alcohol 0.15 and 0.30 g/kg. This was related to an inhibition of gastric ADH activity, as shown by in vitro studies. Ranitidine inhibited gastric ADH to a similar extent on a molar basis, but its effect on alcohol levels in vivo was less constant in various studies. Nizatidine also reduced gastric alcohol first-pass metabolism, but famotidine and roxatidine did not show this effect. In other studies, H2-receptor antagonists did not change AUC and peak alcohol concentration. The controversy is not easy to resolve, since a number of the positive studies did not use a placebo-controlled, randomised, crossover design, while some of the negative studies did not exclude habitual alcohol consumers and included Oriental volunteers, although both groups have been shown to lack significant gastric ADH activity. In this case, when first-pass metabolism of alcohol does not exist, this by definition cannot be abolished by H2-antagonists. The inclusion of oral and intravenous dosage data of alcohol is mandatory to positively identify first-pass metabolism in any individuals. The significance of the effect of H2-antagonists on blood alcohol concentrations is minor. It only occurs in young, male, nonalcoholic, non-Asian individuals, and alcohol must be given in a small (social) dose, in a high concentration, and after meals. An increase in alcohol levels in predisposed patients during treatment with some H2-antagonists cannot be excluded, although the likelihood is small. Furthermore, carefully designed studies are needed to clarify fully the significance of this interaction.

Alcohol and the liver: 1994 update

This article reviews current concepts on the pathogenesis and treatment of alcoholic liver disease. It has been known that the hepatotoxicity of ethanol results from alcohol dehydrogenase-mediated excessive generation of hepatic nicotinamide adenine dinucleotide, reduced form, and acetaldehyde. It is now recognized that acetaldehyde is also produced by an accessory (but inducible) microsomal pathway that additionally generates oxygen radicals and activates many xenobiotics to toxic metabolites, thereby explaining the increased vulnerability of heavy drinkers to industrial solvents, anesthetics, commonly used drugs, over-the-counter medications, and carcinogens. The contribution of gastric alcohol dehydrogenase to the first-pass metabolism of ethanol and alcohol-drug interactions is discussed. Roles for hepatitis C, cytokines, sex, genetics, and age are now emerging. Alcohol also alters the degradation of key nutrients, thereby promoting deficiencies as well as toxic interactions with vitamin A and beta carotene. Conversely, nutritional deficits may affect the toxicity of ethanol and acetaldehyde, as illustrated by the depletion in glutathione, ameliorated by S-adenosyl-L-methionine. Other "supernutrients" include polyunsaturated lecithin, shown to correct the alcohol-induced hepatic phosphatidylcholine depletion and to prevent alcoholic cirrhosis in nonhuman primates. Thus, a better understanding of the pathology induced by ethanol is now generating improved prospects for therapy.

Alcohol consumption and alcohol pharmacokinetics: interactions within the normal population

We have analyzed the interrelationships between habitual alcohol consumption, peak blood alcohol concentration after a standard dose, and rate of alcohol metabolism in a group of 199 male and 213 female twins. Both peak concentration and rate of metabolism are strongly associated with alcohol consumption levels, even in the range of 0-10 g of alcohol/day. The peak concentration and rate of metabolism were strongly correlated in both men and women; this is not due to their common dependence on alcohol intake nor to experimental error. These results show that the threshold for effects of habitual consumption on alcohol pharmacokinetics is much lower than previously suspected, and that there are factors that reduce preabsorptive or first-pass metabolism but increase postabsorptive metabolism.

Famotidine increases plasma alcohol concentration in healthy subjects

The effect of famotidine on plasma alcohol concentration was studied in 24 healthy male subjects who demonstrated high apparent ethanol first-pass metabolism after oral (p.o.) and intravenous (i.v.) ethanol administration (i.e. AUC(po) < or = 40% of AUC(i.v.), where AUC is area under the plasma ethanol concentration-time curve). Six of the original 30 subjects screened (20%) did not demonstrate high first-pass metabolism and were excluded. In a randomized open crossover study, oral ethanol pharmacokinetics were assessed after breakfast in the morning following a 3-day regimen of famotidine, 40 mg/day, and following a no-drug control period. Famotidine increased the area under the plasma ethanol concentration-time curve (AUC0-t) by 29% (7.1 vs 5.5 mg.h/dL, P = 0.006) and maximal plasma concentration (Cmax) by 23% (9.2 vs 7.5 mg/dL, P = 0.013). The changes in ethanol AUC0-t and Cmax may have been associated with changes in gastric emptying, as they were inversely correlated with changes in the time at which maximal plasma concentration was attained. There was considerable intra-individual variation in ethanol AUC and Cmax. As a result, regression to the mean is a potentially confounding problem in ethanol pharmacokinetic studies when subjects are selected on the basis of having low AUC(po), and properly controlled randomized studies of substantial size are required to detect modest drug effects. Small effects on ethanol pharmacokinetics have now been demonstrated with all four of the major H2-receptor antagonists, but these effects are seen only under specific experimental conditions and appear to be unimportant clinically.

Aetiology and pathogenesis of alcoholic liver disease

Until the 1960s, liver disease of the alcoholic patient was attributed exclusively to dietary deficiencies. Since then, however, our understanding of the impact of alcoholism on nutritional status has undergone a progressive evolution. Alcohol, because of its high energy content, was at first perceived to act exclusively as 'empty calories' displacing other nutrients in the diet, and causing primary malnutrition through decreased intake of essential nutrients. With improvement in the overall nutrition of the population, the role of primary malnutrition waned and secondary malnutrition was emphasized as a result of a better understanding of maldigestion and malabsorption caused by chronic alcohol consumption and various diseases associated with chronic alcoholism. At the same time, the concept of the direct toxicity of alcohol came to the forefront as an explanation for the widespread cellular injury. Some of the hepatotoxicity was found to result from the metabolic disturbances associated with the oxidation of ethanol via the liver alcohol dehydrogenase (ADH) pathway and the redox changes produced by the generated NADH, which in turn affects the metabolism of lipids, carbohydrates, proteins and purines. Exaggeration of the redox change by the relative hypoxia which prevails physiologically in the perivenular zone contributes to the exacerbation of the ethanol-induced lesions in zone 3. In addition to ADH, ethanol can be oxidized by liver microsomes: studies over the last twenty years have culminated in the molecular elucidation of the ethanol-inducible cytochrome P450IIE1 (CYP2E1) which contributes not only to ethanol metabolism and tolerance, but also to the selective hepatic perivenular toxicity of various xenobiotics. Their activation by CYP2E1 now provides an understanding for the increased susceptibility of the heavy drinker to the toxicity of industrial solvents, anaesthetic agents, commonly prescribed drugs, 'over the counter' analgesics, chemical carcinogens and even nutritional factors such as vitamin A. Ethanol causes not only vitamin A depletion but it also enhances its hepatotoxicity. Furthermore, induction of the microsomal pathway contributes to increased acetaldehyde generation, with formation of protein adducts, resulting in antibody production, enzyme inactivation and decreased DNA repair; it is also associated with a striking impairment of the capacity of the liver to utilize oxygen. Moreover, acetaldehyde promotes glutathione depletion, free-radical mediated toxicity and lipid peroxidation. In addition, acetaldehyde affects hepatic collagen synthesis: both in vivo and in vitro (in cultured myofibroblasts and lipocytes), ethanol and its metabolite acetaldehyde were found to increase collagen accumulation and mRNA levels for collagen. This new understanding of the pathogenesis of alcoholic liver disease may eventually improve therapy with drugs and nutrients.

Epidemiology of alcoholic liver disease

Although mortality from alcoholic liver disease has declined in some Western countries in recent years, elsewhere it is increasing and overall it remains a major health problem. Deaths are predominantly seen in patients with alcoholic hepatitis or cirrhosis, and when they occur in patients with fatty liver are usually unrelated to liver disease. Progression to cirrhosis is correlated with the severity of fatty liver and particularly with the presence of alcoholic hepatitis. Mortality from cirrhosis is strongly correlated with per capita alcohol consumption. The decline in cirrhosis mortality rates seen recently is related in part to decreases in per capita consumption, but probably also to the growth of self-help organizations which facilitate abstinence from alcohol. Recent studies suggest there is not an invariable dose-response relationship between alcohol intake and the severity of liver disease and that alcohol has a permissive effect which allows other aetiological factors to operate. Factors that influence susceptibility to alcoholic liver disease include gender (women develop alcoholic cirrhosis more readily than men), concomitant hepatitis C infection and possibly hepatitis B infection. It is uncertain whether HLA status or immune mechanisms are implicated. The systematic use of screening tests for hazardous consumption combined with early intervention therapies offers a good prospect of reducing morbidity and mortality from alcoholic liver disease.

Apoptotic bodies in a murine model of alcoholic liver disease: reversibility of ethanol-induced changes

The aim of this study was to investigate the effects of ethanol exposure on the location and number of apoptotic bodies in murine liver. Livers from 21 control mice were compared with those of 41 animals exposed to ethanol vapour by inhalation for up to 23 days. In the control livers, apoptotic bodies were identified in association with 36 per cent of the terminal hepatic venules examined and 88 per cent of these bodies were located in the first two rows of perivenular hepatocytes. By comparison, in the ethanol-exposed group, apoptotic bodies were observed in association with 72 per cent of the terminal hepatic venules examined and more were found further from them. This increase in the number of apoptotic bodies was shown to depend on the duration of ethanol exposure and, furthermore, the effects of ethanol were shown to be completely reversed by a period of abstinence. These results indicate that ethanol exposure has time-dependent, reversible effects on both the location and the number of apoptotic bodies in murine liver. This extends knowledge gained from previous work on rat livers.

Ethanol metabolism in deermice: role of extrahepatic alcohol dehydrogenase

The relative contributions to ethanol metabolism of extrahepatic alcohol dehydrogenase (ADH) and of liver microsomes were assessed in deermice, which lack hepatic low Km ADH (ADH-). In vitro kinetic studies showed the existence of high Km (> 1 M) ADH activity in the liver and kidney, and an enzyme with intermediate Km in the gastric mucosa (Km = 133 mM), whereas the low Km ADH was missing. With deuterated ethanol, ADH- deermice showed a significant exchange of reducing equivalents that had been equated with ethanol metabolism by others, whereas we found a poor correlation between the rate of exchange and the rate of metabolism. In vitro studies with subcellular fractions, isolated hepatocytes, and tissue slices revealed that neither liver, nor kidney, nor stomach from ADH- deermice contributed to exchange of reducing equivalents. These findings clearly indicated that the ADHs with high or intermediate Km of the tissues studied are not responsible for the exchange. Furthermore, gastrectomized ADH- deermice still showed an exchange of reducing equivalents, thereby dissociating exchange from gastric ADH activity. Moreover, pretreatment with cimetidine (50 mg/kg body weight), an inhibitor of gastric ADH, did not alter the rate of total ethanol elimination when ethanol was given intraperitoneally. In conclusion, when ethanol was given parenterally, the microsomal ethanol-oxidizing system rather than gastric ADH is a major pathway of ethanol oxidation in ADH- deermice, whereas both pathways contribute significantly to the metabolism of orally administered ethanol.

Comparative trial in volunteers to investigate possible ethanol-ranitidine interaction

OBJECTIVE

To assess the effect of ranitidine on ethanol absorption after ethanol 0.5 g/kg is given in three single doses of 0.167 g/kg to simulate normal social drinking.

DESIGN

A double-blind, placebo-controlled, crossover trial was performed in 16 healthy men. Ethanol serum concentrations were measured on day 6 of each of the three treatment periods (placebo, ranitidine 150 mg bid, or ranitidine 300 mg bid).

METHODS

Ethanol 0.167 g/kg was administered followed by a standard meal at 1700. The last tablet of the test medication was given 15 minutes later. Thirty and 60 minutes after the first intake, the same amount of ethanol was given again. Serum ethanol concentrations were measured multiple times during the four-hour period following oral ingestion of the first dose.

RESULTS

Comparison of median serum ethanol concentrations, the areas under the curve, peak and time to peak serum ethanol concentrations showed no significant differences during medication with placebo, ranitidine 150 mg bid, or ranitidine 300 mg bid. Peak ethanol concentrations (median values) were 153, 140, and 155 mg/L, respectively.

CONCLUSIONS

This study shows that treatment with ranitidine, in a dose up to 300 mg bid, has no significant effect on serum ethanol concentrations, even when ethanol was given in divided doses to simulate normal patterns of social drinking. This implies that concomitant dosing with ranitidine will not increase the adverse effects of moderate doses of ethanol on concentration and psychomotor function.

Review article: lack of clinical significance of the interaction between H2-receptor antagonists and ethanol

It has been proposed that an appreciable fraction of ingested ethanol is metabolized in the gastric mucosa and that inhibition of this metabolism by H2-receptor antagonists produces clinically important increases in blood ethanol. This paper reviews available data concerning gastric metabolism of ethanol and the influence of H2-antagonists on ethanol metabolism. It concludes that very little, if any, metabolism of ethanol is likely to occur in the gastric mucosa, and the interaction between H2-antagonists and ethanol is clinically insignificant.

Adaptive protection related to clearance of ethanol in gastric mucosa of cats

This study was designed to test the hypothesis that hyperemia after exposure to 2 M NaCl protects the gastric mucosa against damage caused by absolute ethanol by removing ethanol diffusing from the gastric lumen into the mucosa. The stomach of anesthetized cats was perfused with saline at pH 1.0. Gastric mucosal blood flow was determined by radioactive microspheres, and portal vein blood flow was measured by Doppler ultrasound flowmetry. The concentration of ethanol in the corpus mucosa and the amount of ethanol transported away from the stomach in portal blood were measured by using absolute ethanol containing trace amounts of 14C-labeled ethanol. Pretreatment with 2 M NaCl for 10 min increased mucosal blood flow and prevented the development of deep mucosal lesions after subsequent application of absolute ethanol. An inverse correlation was found between mucosal blood flow and the degree of ethanol-induced damage. The mucosal content of ethanol was low in animals pretreated with hyperosmolar NaCl, and the degree of mucosal damage was related to the tissue concentration of ethanol. The amount of ethanol transported by blood from the stomach increased with increasing mucosal blood flow. We conclude that the mild irritant, 2 M NaCl, increases mucosal blood flow, which protects the mucosa by removing ethanol diffusing from the lumen. Thus, the mucosal ethanol concentration remains below a level that causes damage.

Liver triglyceride concentration and body protein metabolism in ethanol-treated rats: effect of energy and nutrient supplementation

The objective of this study was to compare the metabolic effects of long-term ethanol consumption with oral (Lieber-DeCarli) and enteral feeding techniques. Enteral feeding allowed administration of greater amounts of energy and nutrients. After 21 days of treatment using the Lieber-DeCarli technique, the ethanol-treated rats had the following significant (P less than 0.05) differences from pair-fed controls: lower cumulative nitrogen balance (days 5-21; 2.8 +/- 0.1 g N vs. 3.5 +/- 0.1 g N), lower protein content of gastrocnemius muscle (289 +/- 17 mg vs. 358 +/- 11 mg) and intestinal mucosa (461 +/- 19 mg vs. 577 +/- 40 mg), higher plasma leucine concentration (147 +/- 8 mumol/L vs. 102 +/- 8 mumol/L), higher liver protein content (2222 +/- 122 mg vs. 1679 +/- 58 mg), and higher liver triglyceride concentration (38.4 +/- 2.8 mg/g vs. 8.7 +/- 1.0 mg/g). When rats received the same amount of nitrogen (1.5 g.kg-1.day-1) and ethanol (13 g.kg-1.day-1) but 16.3% more energy and nutrients by a surgically implanted gastric cannula (enterally fed), the effects of ethanol on nitrogen balance, tissue protein content, plasma leucine concentration, and liver triglyceride concentration were similar to those observed in the rats fed orally. It is concluded that the metabolic effects observed using the Lieber-DeCarli feeding technique are due to ethanol per se and not the synergism of ethanol and undernutrition as recently suggested.

First-pass gastric mucosal metabolism of ethanol is negligible in the rat

Ethanol metabolism by gastric alcohol dehydrogenase (ADH) is thought to be an important determinant of peripheral ethanol time-concentration curves (AUCs) in rats and humans. We quantitated this metabolism in rats by measuring the gastric absorption of oral ethanol (0.25 g/kg) and the gastric venous-arterial (V-A) difference of ethanol versus ethanol metabolites (acetate, acetaldehyde, and bicarbonate). Over 1 h, approximately 20% of the ethanol was absorbed from the stomach and 70% was emptied into the duodenum. The gastric V-A difference of ethanol metabolites was less than 4% of that of ethanol. Thus, gastric metabolism accounted for less than 1% (less than 4% of 20% absorbed) of the dose. This negligible metabolism was predictable from the low affinity of gastric ADH for ethanol. In contrast, gastric ADH has a high affinity for octanol, and 66% of this compound was metabolized during gastric absorption. Evidence supporting gastric metabolism of ethanol largely derives from the lower AUCs observed after oral than after intravenous administration; however, we observed increasingly higher AUCs with increasingly rapid portal vein infusions of identical ethanol doses. We conclude that gastric metabolism of ethanol is negligible in the rat, and differences in AUCs ascribed to gastric metabolism may reflect differences in ethanol absorption.

Alcohol consumption and the risk of cirrhosis

OBJECTIVE

To determine risk levels for the development of cirrhosis in Australian men who consume alcohol and to compare this risk with that of Australian women.

DESIGN AND SETTING

A case-control study using an interview technique, based in two major tertiary referral hospitals in Sydney.

PATIENTS

Forty-three men with newly diagnosed cirrhosis of the liver and a total of 115 male control subjects, age matched with the case subjects. The data for women (36 cases and 99 controls) have been reported previously.

RESULTS

The risk of men developing cirrhosis increases significantly above the baseline when the alcohol intake exceeds 40 g per day. The risk to women is significant at a similar intake level. Dietary intake and past major illnesses appear to have no role in determining risk.

CONCLUSION

The recommended safe drinking level for men and women should be 40 g per day, as suggested by the National Health and Medical Research Council.

Gastric emptying in the acutely inebriated patient

Fifty inebriated emergency department (ED) patients underwent evacuation of gastric contents via a nasogastric tube, in order to determine if a significant amount of ingested ethanol can be removed prior to absorption. Such a result could potentially reduce additional intoxicating effect. The gastric contents were assayed for total ethanol concentration, and a potential (postabsorption) additive blood alcohol level (PABAL) was projected and compared to the actual BAL on arrival. The type of beverage ingested and the time since last drink were recorded. BAL ranged from 108 to 637 mg/dL (mean +/- SD, 290 +/- 104.7). Gastric aspirate volume ranged from 50 to 700 mL (190 +/- 134), and contained alcohol in a range of 87 to 2271 mg/dL (475 +/- 479). Based on the distribution volume for alcohol calculated according to the patient's weight, this corresponded to a PABAL of 3 to 167 mg/dL (mean, 24.3 +/- 29.3). There was no significant correlation between the volume or concentration of gastric aspirate and the patient's stated drinking history. The authors conclude that a significant amount of ingested alcohol may occasionally be removed from absorption by the routine evacuation of gastric contents in intoxicated patients. These patients cannot be identified upon presentation, however, and these data cannot support routine use of gastric emptying in the detoxification of inebriated patients.

Concentration-time profiles of ethanol in capillary blood after ingestion of beer

Blood ethanol profiles were determined in experiments with healthy volunteers after they had drunk beer. When 330 ml of light beer (1.8% w/v ethanol) was consumed in 5 min by four men and four women, the average peak blood-alcohol concentration (BAC) reached was 8 mg/100 ml (range 2-11). After nine men had drunk 660 ml of beer (3.0% w/v or 3.6% w/v ethanol) in 25 minutes on an empty stomach, the average peak BAC was 32 mg/100 ml (range 26-44) and 37 mg/100 ml (range 23-54) respectively. When the same two beers were consumed by another nine men together with a meal, the peak BAC was 24 mg/100 ml (range 20-29) and 28 mg/100 ml (range 20-39) respectively. The peak BAC occurred earlier when beer was ingested together with food; mean 32 min (range 30-50) compared with 41 min (range 30-70) with an empty stomach. The rate of disappearance of alcohol from blood (beta-slope) was 12 mg/100 ml/h in the fed state and 15 mg/100 ml/h when subjects were fasted. The apparent volume of distribution of ethanol (Vd) was 0.65 l/kg (SD 0.07) for the empty stomach condition but exceeded unity when beer was ingested together with food. It seems that part of the dose of alcohol when consumed with food never reaches the systemic circulation.

Cancer incidence following subtotal gastrectomy

Hawaiian Japanese men (n = 432) who had undergone subtotal gastrectomy for peptic ulcers before 1971-1975 were followed up for detection of cancer development. They showed a significant increase in colon cancer risk (P = 0.008) and lung cancer risk (P = 0.002) compared with 6161 nongastrectomized men. The association with lung cancer persisted after adjustment for cigarette use (P = 0.03). Alcohol consumption was associated with colonic cancer in this cohort, and gastrectomized men consumed more alcohol than nongastrectomized men; however, the association of gastrectomy with colon cancer persisted after adjustment for alcohol use (P = 0.02). Gastrectomized men were lighter and had lower serum lipid levels than controls, suggesting that undernutrition might favor the development of some cancers. The type of gastroenteric anastomosis did not influence the cancer risk level in the colon or lung.

Effect of concentration of ingested ethanol on blood alcohol levels

The effect of the concentration of ingested ethanol on the resulting blood alcohol concentrations (BAC) was tested in both humans and rats. In humans, when 0.3 g/kg body weight ethanol was ingested postprandially, the mean area under the blood alcohol curve (AUC) and the mean peak BAC were significantly lower with a concentrated (40% w/v) than with a dilute (4%) solution. Similarly, rats in the fed state exhibited decreasing mean AUCs with increasing concentrations (4%, 16%, and 40%) of intragastrically administered ethanol (1.0 g/kg). Pharmacokinetic analysis comparing intragastric and intraperitoneal administration of ethanol to rats indicated that the more concentrated solution resulted in less alcohol reaching the systemic circulation (4%: 0.896 +/- 0.074 g/kg: 16% 0.772 +/- 0.072 g/kg; 40%: 0.453 +/- 0.037 g/kg) and suggested that this affect could be attributed to two factors: increased gastric retention of ethanol (4%: 0.109 +/- 0.024 g/kg; 16%: 0.102 +/- 0.016 g/kg; 40%: 0.214 +/- 0.042 g/kg) and a large increase in first-pass metabolism (4%; 0.004 +/- 0.054 g/kg; 16%: 0.145 +/- 0.048 g/kg; 40%: 0.329 +/- 0.044 g/kg). In contrast to the results in the fed state, in humans fasted overnight the concentration of alcohol consumed (4%, 16%, and 40%) had no significant effect on mean AUCs. In fasted rats, mean AUCs after intragastric intubation of the two lower concentrations of ethanol (4% and 16%) were comparable to those found after intraperitoneal injection, and only the highest ethanol concentration (40%) produced a lower mean AUC.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of ranitidine, cimetidine or famotidine on low-dose post-prandial alcohol absorption

Plasma alcohol concentration following oral ingestion of 0.3 g/kg of alcohol (ethyl alcohol), one hour after an evening meal, was measured in four groups of 12 healthy subjects. Each group had a control study and a repeat study after 7 days dosing with either placebo or an H2-receptor antagonist (300 mg ranitidine nocte, 800 mg cimetidine nocte, or 40 mg famotidine nocte). There was no significant difference between the control and post-dosing studies in the integrated 4-h plasma alcohol concentration, peak plasma alcohol concentration, or time to reach peak alcohol concentration. This study shows that post-prandial alcohol absorption after 0.3 g/kg of alcohol is not affected by ranitidine, cimetidine or famotidine.

Effect of dihydrotestosterone on the rate of ethanol elimination in healthy men

Testosterone (T) and, more potently, dihydrotestosterone (DHT), are in vitro inhibitors of hepatic alcohol dehydrogenase (ADH). An increase in the rate of ethanol disappearance (RED) in man has been observed after orchidectomy. We thus investigated the influence of DHT administration on RED in 10 healthy male volunteers. RED was estimated after an oral ethanol bolus (0.6 g/kg), before and after a 14-day treatment with DHT (2 x 125 mg per day percutaneously; Andractim, Besins iscovesco, France). A mean 11.5-fold increase in DHT levels and a 2.0-fold decrease in T values were observed after DHT administration, confirming the good compliance with treatment. RED was decreased after DHT (0.168 +/- 0.043 vs. 0.137 +/- 0.043 g/l/hr; mean +/- SD; p less than 0.01 using Wilcoxon's paired comparison test). These data are consistent with a DHT-induced inhibition of hepatic ADH in vivo. This could have a beneficial effect by decreasing acetaldehyde production in alcoholic patients, in whom marked hypoandrogenism frequently occurs.

Antibodies against acetaldehyde-modified epitopes: an elevated IgA response in alcoholics

Several recent reports have shown that antibodies reactive with acetaldehyde (AcH)-modified epitopes are present in alcoholics. However, similar antibodies have also been found in patients with non-alcoholic liver disease and control subjects. In each of these studies total immunoglobulin binding to the AcH-modified proteins was measured, with no attempt being made to identify the classes of immunoglobulin involved. In the present study we employed an enzyme-linked immunosorbent assay (ELISA) to assess the classes of immunoglobulin involved in this response, using plasma samples from 97 alcoholics with varying degrees of liver disease, 35 patients with non-alcoholic liver disease and 33 control subjects. All three groups exhibited a large IgM response and a negligible IgG response. However, the alcoholics exhibited a significantly higher IgA response than either of the other groups. This suggests that the measurement of the IgA response to AcH-modified epitopes may be a specific marker of ethanol abuse.

Cigarette smoking and rate of gastric emptying: effect on alcohol absorption

OBJECTIVE

To examine the effects of cigarette smoking on alcohol absorption and gastric emptying.

DESIGN

Randomised crossover study.

SETTING

Research project in departments of medicine and nuclear medicine.

SUBJECTS

Eight healthy volunteers aged 19-43 who regularly smoked 20-35 cigarettes a day and drank small amounts of alcohol on social occasions.

INTERVENTIONS

Subjects drank 400 ml of a radiolabelled nutrient test meal containing alcohol (0.5 g/kg), then had their rates of gastric emptying measured. Test were carried out (a) with the subjects smoking four cigarettes an hour and (b) with the subjects not smoking, having abstained for seven days or more. The order of the tests was randomised and the tests were conducted two weeks apart.

MAIN OUTCOME MEASURES

Peak blood alcohol concentrations, absorption of alcohol at 30 minutes, amount of test meal emptied from the stomach at 30 minutes, and times taken for 50% of the meal to leave the proximal stomach and total stomach.

RESULTS

Smoking was associated with reductions in (a) peak blood alcohol concentrations (median values in non-smoking versus smoking periods 13.5 (range 8.7-22.6) mmol/l v 11.1 (4.3-13.5) mmol/l), (b) area under the blood alcohol concentration-time curve at 30 minutes (264 x 10(3) (0-509 x 10(3)) mmol/l/min v 140 x 10(3)) (0-217 x 10(3) mmol/l/min), and (c) amount of test meal emptied from the stomach at 30 minutes (39% (5-86%) v 23% (0-35%)). In addition, smoking slowed both the 50% gastric emptying time (37 (9-83) minutes v 56 (40-280) minutes) and the intragastric distribution of the meal. There was a close correlation between the amount of test meal emptied from the stomach at 30 minutes and the area under the blood alcohol concentration-time curve at 30 minutes (r = 0.91; p less than 0.0001).

CONCLUSION

Cigarette smoking slows gastric emptying and as a consequence delays alcohol absorption.

The drug interaction potential of ranitidine: an update

Ranitidine is a H2-receptor antagonist widely used in the treatment of a variety of gastrointestinal disorders. Since cimetidine--the predecessor drug of ranitidine--interacts with a variety of other agents and moreover ranitidine is often administered in combination with other drugs the interaction potential of ranitidine has been subject to extensive investigations. This review updates the information available from 1988 to present. Pharmacokinetic interactions of ranitidine with other drugs may occur at the site of absorption, metabolism and renal excretion. Most of the interactions reported at each of the three levels are minor and of low clinical significance. In view of some uncontrolled anecdotal reports, one cannot completely rule out the possibility that ranitidine might have some limited interaction potential in special patient populations under certain clinical conditions. However, it must be emphasized that numerous controlled studies have proven that ranitidine can be safely coadministered with other drugs.