Blood-alcohol level, tests

Alcohol and Car Driving The effects of alcohol and driving are a subject of great importance, as many countries have made laws designed to prevent car accidents. Accidents involving alcohol number as many as 50% of total accidents (Fig. 14-1). Hence, it is necessary to perform breath or blood tests to determine a driver s alcohol content. In the United Kingdom, a blood-alcohol level exceeding 80 mg/100 mL is an offense other countries such as the United States and Australia have lower limits. 

A more down-to-Earth use of fuel cells is found in traffic-law enforcement. Police officers need quick and simple ways to determine a person s blood alcohol level in the field. In the time it takes to bring a person to the station or to a hospital for a blood or urine test, the person s blood alcohol content (BAG) might change. Fuel cells, such as the one in the device shown above, provide a quick and accurate way to measure BAG from a breath sample. The alcohol ethanol from the person s breath is oxidized to acetic acid at the anode. At the cathode, gaseous oxygen is reduced and combined with hydronium ions (released from the anode) to form water. The reactions generate an electric current. The size of this current is related to the BAG. 

As already stated, the source of biological material is also important either due to its accessibility (i.e., noninvasive nature) or due to the fact that the analytes to be measured are restricted to certain locations. Biomarkers can be detected in all biological entities (i.e., fluids, gases, and tissues), and depending on what is to be measured each biological source has a specific niche. For example the fact that alcohol is excreted in the lung, combined with the convenience of using exhaled air, has been exploited for many years in the breathalyzer test as an indirect measurement of blood alcohol levels [5 ]. Stool is commonly used for the detection of parasites and infections. Tears have been proposed to detect and treat ocular toxicity [6], Urine has also been used extensively to measure both renal and non-renal injuries. However, for the most part, blood (serum or plasma) and urine are the most utilized sources. 

The exact color produced depends on the amount of alcohol in the breath. The color change that is produced during the test is compared to standard color mixtures of the two chromium ions to get an estimate of the blood alcohol level. 

In a study designed to test the effeets of acute alcohol intoxication in epileptics, 25 patients were given a 12 oz (about 340 mL) drink of alcohol 25%. Blood-alcohol levels ranged from 39 to 284 mg%. All patients had signs of alcohol intoxication without any effect on seizure frequency. The metabolism of a single dose of phenytoin was not affected in one study in healthy subjects by the acute ingestion of alcohol. However, the manufacturers say that acute alcoholic intake may increase phenytoin serum levels. ... 

A double-blind crossover study in 12 healthy subjects found that a transdermal hyoscine preparation (Scopoderm-TTS) did not alter the effects of alcohol on the performance of several psychometric tests (Critical Flicker Fusion Frequency, Choice Reaction Tasks), nor was the clearance of alcohol or hyoscine changed. Blood-alcohol levels of up to 80 mg%, and 130 mg%, were studied. Nevertheless, the manufacturer suggests... 

Caffeine does appear to improve some of the detrimental effects of alcohol in some psychomotor tests, which is probably why there is a longstanding and time-hallowed belief in the value of strong black coffee to sober up those who have drunk too much. In addition, it is just possible that the time taken to drink the coffee gives the liver just a little more time to metabolise some of the alcohol. However, it seems that it is not effective in all aspects of alcohol impairment, particularly subjective effects. In addition, caffeine does not reduce blood-alcohol levels. Coffee and other sources of caffeine do not make it safe to drive or handle dangerous machinery, and it may even make drivers more accident-prone. 

A study in 22 subjects, given meprobamate 400 mg four times daily for one week, showed that with blood-alcohol levels of 50 mg% their performance of a number of coordination and judgement tests was much more impaired than with either drug alone. Four of the subjects were quite obviously drunk while taking both meprobamate and alcohol showed marked incoordination and social disinhibition. Two could not walk without assistance. The authors say this effect was much greater than anything seen with alcohol alone. 

A study in a large number of healthy subjects showed that the performance of various psychomotor skills related to driving (choice reaction, coordination, divided attention tests) were impaired by single doses of indometacin 50 mg or phenylbutazone 200 mg. Alcohol 0.5 g/kg made things worse in those taking phenylbutazone, but the performance of those taking indometacin was improved to some extent. The reasons are not understood. The study showed that the subjects were subjectively unaware of the adverse effects of phenylbutazone. Information is very limited, but patients should be warned if they intend to drive. In two studies, ibuprofen 800 mg had no significant effect on blood-alcohol levels of healthy subjects. ... 

A double-blind, crossover study in 17 healthy subjects found that the inhalation of 40 mg of sodium cromoglicate had little or no effect on the performance of a number of tests on human perceptual, cognitive, and motor skills, whether taken alone or with alcohol 0.75 g/kg. Nor did it affect blood-alcohol levels. This is in line with the common experience of patients, and no special precautions seem to be necessary. 

The concurrent use of fluoxetine 30 to 60 mg and alcohol (4 oz of whiskey) did not affect the pharmacokinetics of either drugs in healthy subjects, and fluoxetine did not alter the effect of alcohol on psychomotor activity (stability of stance, motor performance, manual co-ordination). Similarly, blood-alcohol levels of 80 mg% impaired the performance of a number of psychomotor tests in 12 healthy subjects, but the addition of fluoxetine 40 mg daily taken for 6 days before the alcohol had little further effect. Another study also found no change in the performance of a number of psychophysiological tests when fluoxetine was combined with alcohol. No problems were found in a study of 20 alcohol-dependent patients taking fluoxetine 60 mg daily when they drank alcohol, or in approximately 31 patients taking fluoxetine 20 mg daily who drank unspecified small quantities of alcohol. ... 

One study found that fluvoxamine 150 mg daily with alcohol impaired alertness and attention more than alcohol alone, whereas another study in subjects given 40 g of alcohol (blood-alcohol levels up to 70 mg%) found no evidence to suggest that the addition of fluvoxamine 50 mg twice daily worsened the performance of the psychomotor tests, and it even appeared to reverse some of the effects. The pharmacokinetics of alcohol were hardly affected by fluvoxamine, but the steady state maximum plasma levels of the fluvoxamine were increased by 20%, although the fluvoxamine AUC was unchanged. It was suggested that administration of alcohol may have promoted dissolution of fluvoxamine and increased the absorption rate without affecting bioavailability. Another study also found that fluvoxamine does not appear to enhance the detrimental effects of alcohol on the performance of psychomotor tests. ... 

Studies in subjects with blood-alcohol levels of 40 to 60 mg% found that clomipramine had only slight or no effects on various choice reaction, coordination, memory and learning tests. A case describes a fatal poisoning in a chronic alcoholic patient taking clomipramine for depression. The ultimate toxic effect was thought to be due to alcohol-induced decreased biotransformation of clomipramine, as post-mortem examination revealed toxic liver damage, and low levels of the metabolite were found in blood and hair samples. ... 

A double-blind, crossover study in 20 healthy subjects given various combinations of alcohol and either doxepin or a placebo found that with blood-alcohol levels of 40 to 50 mg% their choice reaction test times were prolonged and the number of mistakes increased. Coordination was obviously impaired after 7 days of treatment with doxepin, but not after 14 days. In an earlier study doxepin appeared to cancel out the deleterious eftects of alcohol on the performance of a simulated driving test. It appears that doxepin may be more toxic when given with alcohol and it has been suggested that a less dangerous alternative could be chosen when indications of alcohol abuse or suicide risk are present. ... 

Breath Tests to Measure Blood Alcohol Level... 

In the process, ethanol is oxidized, and the chromium reagent is reduced. The new chromium compound is a different color, and therefore, the progress of the reaction can be monitored by the color change from reddish-orange to green. This reaction formed the basis for many of the early breath tests that assessed the level of blood alcohol. Breath tests that utilize this reaction are still commercially available. The test consists of a tube, where one end is fitted with a mouthpiece and the other end has a bag. The inside of the tube contains sodium dichromate that is adsorbed onto the surface of an inert solid, such as silica gel. As the user blows air through the tube and fills up the bag, the alcohol in the user s breath reacts with the... 

A breathalyser (Figure 9.16) uses sodium dichromate(vi) to oxidize alcohol in breath to ethanoic acid. The sodium dichromate(vi) changes color from orange to green when consumed by the reaction. The extent of this colour change is monitored and used to determine the blood alcohol level of the person undergoing the test. 

The test that law enforcement agencies use to approximate a person s blood alcohol level is based on the oxidation of breath ethanol. An oxidizing agent impregnated onto an inert material is enclosed within a sealed glass tube. When the test is to be administered, the ends of the tube are broken off and replaced with a mouthpiece at one end and a balloon-type bag at the other. The person being tested blows into the mouthpiece until the bag is filled with air. 

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