For social and historical reasons alcohol is usually bought from a store or in a bar or restaurant,rather than from a pharmacy, because it is considered to be a drink and not a drug. However, pharmacologically it has much in common with medicinal drugs that depress central nervous system. Objective tests show that as blood-alcohol levels rise, ability to perform a number of skills gradually deteriorates as brain becomes progressively disorganised. The myth that alcohol is a stimulant has arisen because at parties and social occasions it helps people to lose some of their inhibitions and it allows them to relax and unwind. Professor JH Gaddum put it amusingly and succinctly when, describing early effects of moderate amounts of alcohol, he wrote that “logical thought is difficult but after dinner speeches easy.” The expansiveness and loquaciousness that are socially acceptable can lead on,with increasing amounts of alcohol, to unrestrained behaviour in normally well-controlled individuals, through to drunkenness, unconsciousness, and finally death from respiratory failure. These effects are all a reflection of progressive and deepening depression of CNS.
table 1 below, gives an indication in very broad terms of reactions of men and women to different amounts and concentrations of alcohol.
On whole women have a higher proportion of fat in which alcohol is not very soluble, their body fluids represent a smaller proportion of their total body mass, and their first-pass metabolism of alcohol is less than men because they have less alcohol dehydrogenase in their stomach walls. Consequently if a man and woman of same weight matched each other, drink for drink, woman would finish up with a blood alcohol level about 50 % higher than man. The values shown assume that drinkers regularly drink, have had a meal and weigh between 9 and 11 stones (55 to 70 kg). Higher blood-alcohol levels would occur if alcohol was drunk on an empty stomach and lower values in much heavier individuals. The liver metabolises about one unit per hour so values will fall with time.
Since alcohol impairs skills needed to drive safely, almost all national and state authorities have imposed maximum legal blood alcohol limits (see table 2 below,). In a number of countries this has been set at 80 mg/100 mL (35 micrograms per 100 mL in breath) but impairment is clearly detectable at lower concentrations, for which reason some countries have imposed much lower legal limits.
Alcohol can interact with many drugs both by pharmacokinetic and/or pharmacodynamic mechanisms. The quantity and frequency of alcohol consumption can affect bioavailability of alcohol and other drugs. Several hepatic enzymes are important in metabolism of alcohol; primarily alcohol dehydrogenases convert alcohol into acetaldehyde, but other enzymes, in particular cytochrome P450 isoenzyme CYP2E1, are also involved, especially in moderate to heavy alcohol consumption. Enzyme induction of CYP2E1 (and possibly other isoenzymes) occurs after prolonged heavy alcohol intake,and this can result in an increased metabolic rate and lower blood levels of drugs metabolised via this system. Conversely, short term binge drinking is likely to cause inhibition of this enzyme group by direct competition for binding sites and therefore decrease metabolism of other drugs.
Probably most common drug interaction of all occurs if alcohol is drunk by those taking other drugs that have CNS depressant activity, result being even further CNS depression. Blood-alcohol levels well within legal driving limit may, in presence of other CNS depressants, be equivalent to blood-alcohol levels at or above legal limit in terms of worsened driving and other skills. This can occur with some antihistamines,antidepressants, anxiolytics, hypnotics, opioid analgesics, and others. This section contains a number of monographs that describe results of formal studies of alcohol combined with a number of recognised CNS depressants, but there are still many other drugs that await study of this kind, and which undoubtedly represent a real hazard.
A less common interaction that can occur between alcohol and some drugs, chemical agents, and fungi, is flushing (Antabuse) reaction. This is exploited in case of disulfiram (Antabuse) as a drink deterrent (see Alcohol + Disulfiram interaction), but it can occur unexpectedly with some other drugs, such as some antifungals and cephalosporins, chlorpropamide and metronidazole, and can be both unpleasant and possibly frightening, but it is not usually dangerous.
After Which? October 1984,page 447 and others.
Belize,Canada,* Cape Verde, Central African Republic, Ghana, Guatemala, Ireland, Kenya, Luxembourg, Malaysia, Malta, Mexico, New Zealand,* Nicaragua, Niger, Paraguay, Seychelles, Singapore, Suriname, Switzerland, Uganda, United Kingdom, United States of America,* Uruguay, Zambia
Bolivia,Ecuador, Honduras
Brazil,Sri Lanka
Argentina,Australia,* Austria, Belarus, Benin, Bosnia & Herzegovina, Bulgaria, Cambodia, Croatia, Denmark, El Salvador, Finland, France, French Polynesia, Germany, Greece, Guinea-Bissau, Iceland, Israel, Italy, Kyrgyzstan, Mauritius, Micronesia (Federated States of), Namibia, Netherlands, Peru, Philippines, Portugal, Slovenia, South Africa, Spain, Thailand, The former Yugoslav Republic of Macedonia, Turkey, United Republic of Tanzania, Venezuela
Chile,Costa Rica, Latvia
Georgia,India, Japan, Republic of Moldova
Estonia,Mongolia, Norway, Poland, Sweden
Guyana,Palau
Armenia,Azerbaijan, Colombia, Czech Republic, Equatorial Guinea, Eritrea, Gambia, Guinea, Hungary, Islamic Republic of Iran, Jordan, Kazakhstan, Malawi, Nepal, Nigeria, Panama, Romania, Russian Federation, Slovakia
China,Comoros, Congo (Brazzaville), Dominican Republic, Ethiopia, Lao People’s Democratic Republic, Togo, Ukraine
Note: For easy comparison legally allowable blood alcohol limits have all been expressed as mg%
(See reference number *)Variations occur within these countries e.g. in Australia no alcohol is allowed for drivers of heavy,dangerous goods, public transport vehicles; learners and drivers under 25
Adapted from WHO Global Status Report: Alcohol policy, Geneva, 2004.
| Table 2 Maximum legally allowable blood alcohol limits when driving in various countries | |
|---|---|
| 80 mg% | Belize, Canada,* Cape Verde, Central African Republic, Ghana, Guatemala, Ireland, Kenya, Luxembourg, Malaysia, Malta, Mexico, New Zealand,* Nicaragua, Niger, Paraguay, Seychelles, Singapore, Suriname, Switzerland, Uganda, United Kingdom, United States of America,* Uruguay, Zambia |
| 70 mg% | Bolivia, Ecuador, Honduras |
| 60 mg% | Brazil, Sri Lanka |
| 52 mg% | Republic of Korea |
| 50 mg% | Argentina, Australia,* Austria, Belarus, Benin, Bosnia & Herzegovina, Bulgaria, Cambodia, Croatia, Denmark, El Salvador, Finland, France, French Polynesia, Germany, Greece, Guinea-Bissau, Iceland, Israel, Italy, Kyrgyzstan, Mauritius, Micronesia (Federated States of), Namibia, Netherlands, Peru, Philippines, Portugal, Slovenia, South Africa, Spain, Thailand, The former Yugoslav Republic of Macedonia, Turkey, United Republic of Tanzania, Venezuela |
| 49 mg% | Chile, Costa Rica, Latvia |
| 40 mg% | Lithuania |
| 35 mg% | Jamaica |
| 33 mg% | Turkmenistan |
| 30 mg% | Georgia, India, Japan, Republic of Moldova |
| 20 mg% | Estonia, Mongolia, Norway, Poland, Sweden |
| 10 mg% | Guyana, Palau |
| 0 mg% | Armenia, Azerbaijan, Colombia, Czech Republic, Equatorial Guinea, Eritrea, Gambia, Guinea, Hungary, Islamic Republic of Iran, Jordan, Kazakhstan, Malawi, Nepal, Nigeria, Panama, Romania, Russian Federation, Slovakia |
| No legislation | China, Comoros, Congo (Brazzaville), Dominican Republic, Ethiopia, Lao People’s Democratic Republic, Togo, Ukraine |