An assessment of gastric emptying by breathalyser

Effects of alcohol on brain oxygenation and brain hypoxia induced by intravenous heroin

Alcohol is the most commonly used psychoactive drug, often taken in conjunction with opioid drugs. Since both alcohol and opioids can induce CNS depression, it is often assumed that alcohol potentiates the known hypoxic effects of opioid drugs. To address this supposition, we used oxygen sensors to examine the effects of alcohol on brain oxygenation and hypoxic responses induced by intravenous heroin in awake, freely moving rats. To eliminate robust sensory effects of alcohol following its oral or intraperitoneal delivery, alcohol was administered directly into the stomach via chronically implanted intragastric catheters at human relevant doses. Alcohol delivered at a 0.5 g/kg dose did not affect brain oxygen levels, except for a weak transient increase during drug delivery. This phasic oxygen increase was stronger at a 2.0 g/kg alcohol dose and followed by a weaker tonic increase. Since alcohol absorption from intragastric delivery is much slower and more prolonged than with intraperitoneal or intravenous injections, the rapid rise of brain oxygen levels suggests that alcohol has a direct action on sensory afferents in the stomach well before the drug physically reaches brain tissue via circulation. Despite slow tonic increases in brain oxygen, alcohol at the 2.0 g/kg dose strongly potentiates heroin-induced oxygen responses, increasing both the magnitude and duration of oxygen decrease. Therefore, under the influence of alcohol, the use of opioid drugs becomes much more dangerous, increasing brain hypoxia and enhancing the probability of serious health complications, including coma and death.

Lower Blood Alcohol Concentration Among HIV-Positive Versus HIV-Negative Individuals Following Controlled Alcohol Administration

BACKGROUND

Although it has been purported that HIV-positive individuals may experience a greater degree of intoxication than HIV-negative individuals following acute alcohol consumption, no research to date has empirically tested this supposition. The present investigation entailed a randomized controlled experiment to identify whether the administration of a weight-specified dose of alcohol would lead to differential blood alcohol concentrations (BACs) among HIV-positive versus HIV-negative men.

METHODS

In a specialized barroom laboratory, 143 men (n = 76 HIV-positive and n = 67 HIV-negative; mean age = 42.9) consumed beverages based on a formulation of 0.7 g alcohol/kg body weight over a 15-minute time frame. BAC was assessed via breathalyzer at 2 set time points (10 and 13 minutes postconsumption) and then periodically until detoxification (BAC < 0.040%). Primary outcomes included (i) area under the curve (AUC), calculated based on all of one's BAC readings, (ii) "BAC-EXP," defined as one's BAC reading 13 minutes postconsumption, and (iii) BAC-PEAK, defined as one's highest recorded BAC reading.

RESULTS

Contrary to predictions, AUC (t(141) = 2.23, p = 0.027), BAC-EXP (t(141) = 2.68, p = 0.008), and BAC-PEAK (t(141) = 2.29, p = 0.023) were significantly lower among HIV-positive versus HIV-negative participants. These effects were sustained in multivariable models controlling for age, race, and AUDIT-based hazardous drinking classification. Among the HIV-positive sample, outcomes did not significantly differ based on HIV viral load detectability, antiretroviral therapy (ART) status, or ART adherence.

CONCLUSIONS

The administration of a controlled, weight-specified dose of alcohol led to lower BACs among HIV-positive versus HIV-negative participants. These differences might derive from decreased body fat percentage and delayed gastric emptying associated with HIV seropositivity; however, additional research is necessary to verify these mechanisms. Unique alcohol dosing formulas based on HIV serostatus may be required in future alcohol administration experiments involving HIV-positive samples.

Alcohol: Gastrointestinal and other Toxicities

This article will focus on the two areas of alcohol injury: first, the gastrointestinal system, primarily liver toxicity and cirrhosis, and second, the human toll in injury, examining injury epidemiology information that estimates alcohol's involvement in trauma. Any pharmacist consulting in any capacity, especially related to gastrointestinal disorders, will need to understand the significant sociological, pathological, pharmacological, and psychological impact of alcohol. Pharmacists providing care, including dispensing many different drugs to patients, should be cognizant of the interacting effects of alcohol and the need to warn patients. Finally, the reader will learn of a case in which a pharmacist was sued for not warning about the use of alcohol with a central nervous system depressant, and the resultant litigation after that lawsuit.

Measurement of gastric emptying rate of solids by means of a carbon-labeled octanoic acid breath test

BACKGROUND

The aim of the present study was to develop a breath test for measuring gastric emptying rate of solids that would induce less radiation exposure than radioscintigraphy and would be applicable to field testing.

METHODS

A test meal was used in which [14C]-octanoic acid was mixed with egg yolk and prepared as a scrambled egg. The test meal was labeled with a second marker, 99mTc-albumin colloid, and simultaneous radioscintigraphic and breath test measurements were performed in 36 subjects, 16 normal controls, and 20 patients with dyspeptic symptoms. Mathematical analysis of the excretion rate of labeled CO2 resulted in the definition of three parameters, i.e., gastric emptying coefficient, gastric half-emptying time, and lag phase.

RESULTS

There was an excellent correlation between the gastric emptying coefficient and the scintigraphic half-emptying time (r = -0.88); between the half-emptying time determined by the breath test and the scintigraphic half-emptying time (r = 0.89); and between the lag phases determined by scintigraphy and those determined by breath test (r = 0.92). 14C can be replaced by 13C for labeling the octanoic acid used in the breath test.

CONCLUSIONS

It is concluded that the octanoic acid breath test is a reliable noninvasive test to measure gastric emptying rate of solids.

The action of cisapride on gastric emptying and the pharmacodynamics and pharmacokinetics of oral diazepam

The effects of the benzamide cisapride (C) (8 mg) i.v. have been compared to placebo (P) in a double blind randomised study. The effects on gastric emptying, the absorption and effects of oral diazepam, and BP and pulse were observed. Cisapride increased the rate of gastric emptying of 500 ml liquid containing diazepam 10 mg (t 1/2 C: 7.4 min, P: 14.9 min). The initial rate of absorption of diazepam contained in the drink was increased by C (AUC 0-1 h C: 328 micrograms h l-1, P: 253 micrograms h l-1, but there was no change in overall bioavailability. This change in diazepam kinetics was associated with a significantly greater impairment in reaction time in the first 45 min after drinking but not in self rated sedation. Cisapride produced a significant tachycardia (e.g. after 10 min C: 82 beats/min, P: 69 beats/min) which probably reflects a peripheral vasodilator action. Cisapride may therefore alter the pharmacokinetics and dynamics of concurrently administered drugs.

General anaesthesia with halothane and drug absorption. The effect of general anaesthesia with halothane and diazepam on postoperative gastric emptying in man

The effect of general anaesthesia with halothane on postoperative absorption of paracetamol was measured in seven patients, after minor surgery on the extremities. Gastric emptying, estimated indirectly by the rise in serum paracetamol following oral administration of the drug, was significantly delayed after general anaesthesia with halothane compared with gastric emptying when general anaesthesia with halothane was not administered. It was furthermore demonstrated that absorption of paracetamol and therefore gastric emptying were normal or nearly normal when diazepam 15 mg was given orally to the same patients 2 weeks later.

Effect of ethanol and pH on the adsorption of drugs to activated charcoal: studies in vitro and in man

The effect of ethanol on the adsorption of aspirin, quinidine and amitriptyline to activated charcoal was studied in vitro at pH 1.2 and 7.0. The adsorption of these drugs was greatly dependent on the charcoal-drug ratio and on the pH. Ethanol (10%) significantly (P less than 0.001) increased the percentage of their unadsorbed fraction at both pHs in vitro. In six healthy volunteers activated charcoal (50 g), ingested 5 min. after aspirin (1000 mg) and quinidine sulfate (200 mg), reduced their bioavailability by about 70% (aspirin) and 99% (quinidine). A significant desorption of aspirin but not that of quinidine from charcoal was obvious on the second and third days and seemed to be related to the effect of pH. The absorption of ethanol was not significantly prevented by charcoal. The concomitant ingestion of alcohol (50 g) with drugs antagonized only slightly the ability of charcoal to reduce the absorption of aspirin and quinidine.

Effect of alcoholic beverages on the pharmacokinetics of doxycycline in man

In a randomized cross-over trial on six healthy medical students, alcohol (lg/kg) ingested as whisky did not modify significantly the absorption of 200 mg of doxycycline (DC) given in two tablets. Cheap red wine with a clear taste of acetic acid postponed the absorption of DC for 2-3 hours without affecting its 24-hour AUC or urinary excretion significantly. Another similar trial with other wines on 8 healthy students suggested that good regular wines do not retard DC absorption irrespective of their tannic acid content. However, acetic acid may postpone DC absorption by possibly slowing the rate of gastric emptying.

Alcohol absorption, gastric emptying and a breathalyser

1 The value of a portable breathlyser (Alcometer AE-M2) in the assessment of gastric emptying after alcohol ingestion was investigated by comparing breath and venous blood alcohol concentrations with simultaneous scintigraphic measurements of gastric emptying rate. 2 Alcohol absorption, as determined by the area under the venous blood alcohol concentration-time curve during the first 30 min, correlated with gastric emptying during the same period, implying dependence of the rate of alcohol absorption on gastric emptying rate. 3 There was no correlation between breath and venous alcohol concentrations during the first 15 min after alcohol ingestion, but a significant correlation was observed thereafter. 4 Breath alcohol measurements may be sufficient to detect gross alterations in gastric emptying but measurements of venous blood alcohol are likely to be more reliable.

Drug interactions with alcohol

Ethanol and drugs can affect each other's absorption, distribution, metabolism, and excretion. When ingested together, ethanol can increase drug absorption by enhancing the gastric solubility of drugs and by increasing gastrointestinal blood flow. However, high concentrations of ethanol induce gastric irritation causing a pyloric spasm which in turn may delay drug absorption and/or reduce bioavailability. The 'quality' of the alcoholic beverage, independent of its ethanol content, can contribute to altered absorption of a drug. Ethanol is not bound to plasma proteins extensively enough to modify drug distribution. However, serum albumin levels in chronic alcoholics may be abnormally low so that some drugs, e.g. diazepam, have an increased volume of distribution. In addition to the amount ingested, the duration of regular intake determines the effect of ethanol on drug metabolism. Acute intake of ethanol inhibits the metabolism of many drugs but long term intake of ethanol at a high level (greater than 200g of pure ethanol per day) can induce liver enzymes to metabolise drugs more efficiently. At the present time there are no accurate means, with the possible exception of liver biopsy, to clinically predict the capacity of an alcoholic to metabolise drugs. Several drugs can inhibit the metabolism of ethanol at the level of alcohol dehydrogenase. Individual predisposition determines the severity of this drug-ethanol interaction. During its absorption phase, ethanol inhibits the secretion of antidiuretic hormone and is also able to induce increased excretion of a drug through the kidneys. However, chronic alcoholics with water retention may show reduced excretion of drugs via this route. At the pharmacodynamic level, ethanol can enhance the deleterious effects of sedatives, certain anxiolytics, sedative antidepressants and antipsychotics and anticholinergic agents, on performance. Mechanisms of lethal interactions between moderate overdoses of ethanol and anxiolytics/opiates/sedatives are poorly understood. On the other hand, certain peptides, 'nonspecific' stimulants, dopaminergic agents and opiate antagonists can antagonise alcohol-induced inebriation to a significant degree.

Pharmacokinetic and concentration-effect studies with intravenous metoclopramide

1 Pharmacokinetic and concentration-effect studies have been carried out following intravenous injection of 10 mg metoclopramide hydrochloride to seven normal male volunteers. 2 It is proposed that a two-compartment model adequately describes the disposition of the drug which is rapidly distributed (T1/2alpha = 4.9 +/- 1.1 min) and eliminated (T1/2beta = 165.7 +/- 20.2 min). Total body plasma clearance of the drug is high (10.9 +/- 1.5 ml min-1 kg-1) and approximates to liver plasma flow. 3 Metoclopramide i.v. increases gastric emptying as measured by an ethanol absorption test (P less than 0.005). The duration of this effect is at least 3 h. 4 Ethanol given after i.v. metoclopramide administration produces significant sedation during the first hour and at 3 h (P less than 0.001). 5 The effect of metoclopramide on gastric emptying, and the degree of sedation induced by ethanol would appear to be related to plasma metoclopramide concentration. 6 Metoclopramide increases serum prolactin to 59 +/- 5.8 microgram/1 at 30 min after injection. There is a linear relationship (r = 0.809) between serum prolactin increase and plasma metoclopramide concentration.

Effect of aluminium hydroxide and glycopyrrhonium on the absorption of ethambutol and alcohol in man

1 The effect of aluminium hydroxide and/or of glycopyrrhonium on the absorption of a single oral 50 mg/kg dose of ethambutol (EMB) was investigated on thirteen tuberculous in-patients and on two groups of healthy volunteers with six subjects each. The EMB concentrations in serum and 10+h urine were measured by colorimetry. 2 In order to assess gastric emptying the healthy volunteers ingested ethanol, either 0.5 g/kg in 10% solution or 0.8 g/kg in 20% solution, simultaneously with the drug, and breath alcohol levels were measured repetitively. 3 Aluminium hydroxide significantly lowered the serum EMB levels of the patients during the first 4 h after the EMB intake. No consistent effect was found in the first student experiment, whereas in the second experiment aluminium hydroxide and glycopyrrhonium, alone or in combination, clearly retarded the EMB absorption. 4 Repeated breath alcohol analysis proved unsuitable to indicate the time course of gastric emptying in these circumstances.

24-hour intragastric acidity and nocturnal acid secretion in patients with duodenal ulcer during oral administration of cimetidine and atropine

Cimetidine markedly inhibits gastric acid secretion, but from the therapeutic point of view it is important to know whether concurrent treatment with an anticholinergic increases its effect. This possibility has been investigated by measuring the 24 h intragastric acidity and nocturnal output of acid in four duodenal ulcer patients, each receiving on separate occasions cimetidine 1 g/day and placebo, atropine 2-4 mg/day and placebo, cimetidine and atropine, or two placebos. Cimetidine alone decreased mean hourly hydrogen ion activity by 63% of control values, decreased mean hourly hydrogen ion concentration (total acid) by 41%, inhibited nocturnal acid secretion by 83% and resulted in half the nocturnal samples being anacidic. Atropine alone had no effect when compared with control and combined treatment with both drugs was not superior to cimetidine alone. Atropine did not affect the absorption or urinary excretion of cimetidine. Fasting serum gastrin concentrations were not changed by any of the treatments. At the doses studied, the combination of cimetidine with an anticholinergic appears to offer no advantages over treatment with the H2-antagonist alone. Cimetidine is the only potent anti-secretory drug that does not cause acute side-effects and this important advantage would be lost if it were given with a maximal dose of an anticholinergic.

The effect of desmethylimipramine on the absorption of alcohol and paracetamol

Many drugs can delay gastric emptying and may thereby impair the absorption of other drugs. Desmethylimipramine (DMI) is an antidepressant with anticholinergic properties which might be expected to delay the rate of gastric emptying. In five out of six subjects, DMI significantly delayed both the absorption of alcohol (assessed by a breathalyser) and of paracetamol, and there was a correlation between the two. The breathalyser can therefore be used to predict the extent to which one may impair the absorption of another drug by its effect on gastrointestinal motility.

Inhibition of gastric emptying and drug absorption by narcotic analgesics

The effect of intramuscular pethidine or diamorphine on gastric emptying and the absorption of orally administered paracetamol was assessed in eight normal subjects. 2 Both drugs produced a significant and striking delay in gastric emptying and absorption of paracetamol. 3 It seems inevitable that pethidine and diamorphine will retard the absorption of other orally administered drugs.

The effect of codeine phosphate on the absorption of ethyl alcohol

The effect of syrup, B.P. and codeine phosphate syrup, B.P.C. on blood alcohol levels was determined in six normal subjects. 2 Treatment with syrup alone had little or no influence on the concentration of ethanol in blood. 3 In contrast, pretreatment with codeine phosphate syrup significantly reduced alcohol absorption, as assessed by the maximum blood levels achieved or the area subtended by the blood concentration-time curve. It is suggested that the diminished absorption of ethanol is related to the pharmacological action of codeine on the stomach. 4 It was considered that the concentration of ethanol in linctuses or syrups containing codeine was unlikely to have any significant effect on the central nervous system.