Standardized Field Sobriety Test Course Metabolism in the Liver

Standardized Field Sobriety Test Course   Metabolism in the Liver 

As soon as the alcohol enters the blood stream, the body starts trying to get rid of it. Some of the alcohol will be directly expelled from the body chemically unchanged.  For example, some alcohol will leave the body in the breath, in the urine, in sweat, in tears, etc. However, only a small portion (about 2-10 %) of the ingested alcohol will be directly eliminated. 

Most of the alcohol a person drinks is eliminated by metabolism. Metabolism is a process of chemical change. In this case, alcohol reacts with oxygen in the body and changes, through a series of intermediate steps, into carbon dioxide and water, both of which are directly expelled from the body. 

Session 2 – Detection and General Deterrence 

Metabolism in the Liver 

• • The liver burns the ethanol (i.e., causes a chemical reaction of ethanol with oxygen) 
• • The process is aided by an enzyme called alcohol dehydrogenase 
• • The ultimate products of the chemical reaction are carbon dioxide and water 
• • Due to metabolism, the average person’s BAC drops by about 0.015/hr 

Notes:_______________________________________________ 

2 51

Standardized Field Sobriety Test Course 

Most of the metabolism of alcohol in the body takes place in the liver. An enzyme known as alcohol dehydrogenase acts to speed up the reaction of alcohol with oxygen. The speed of the reaction varies somewhat from person to person, and even from time to time for any given person. On the average, however, a person's blood alcohol concentration --after reaching peak value --will drop by about 0.015 per hour.  For example, if the person reaches a maximum BAC of 0.15, it will take about ten hours for the person to eliminate all of the alcohol. 

For the average sized male, a BAC of 0.015 is equivalent to about two thirds of the alcohol content of a standard drink (i.e., about two thirds of a can of beer, or glass of wine or shot of whiskey).  For the average sized female, that same BAC would be reached on just one half of a standard drink. So the typical male will eliminate about two thirds of a drink per hour, while the typical female will burn up about one half of a drink in that hour. 

Session 2 – Detection and General Deterrence 

Notes:_______________________________________________ 

Metabolism 

How can we speed up the metabolism of alcohol? 

• • We can't speed it up 
• • Drinking coffee won’t help 
• • A cold shower won’t help 
• • Exercise won’t help 

The liver takes its time burning up the alcohol 

2 52

Standardized Field Sobriety Test Course 

We can control the rate at which alcohol enters our bloodstream.  For example, we can gulp down our drinks, or slowly sip them. We can drink on an empty stomach, or we can take the precaution of eating before drinking. We can choose to drink a lot, or a little.  But once the alcohol gets into the blood, there is nothing we can do to affect how quickly it leaves.  Coffee won't accelerate the rate at which our livers burn alcohol. Neither will exercise, or deep breathing, or a cold shower. We simply have to wait for the process of metabolism to move along at its own speed. 

Session 2 – Detection and General Deterrence 

Notes:_______________________________________________ 

Dose Response Relationships 

How much can a person drink before becoming impaired? Depends… 

• • Time? 
• • Sex? 
• • Size? 
• • Drinking on empty stomach? …A couple of beers can do it! 

2 53

Standardized Field Sobriety Test Course 

Dose Response Relationships 

People sometimes ask, "how 'high' is 'drunk'?" What is the "legal limit" for "drunk driving"? How much can a person drink before becoming "impaired"? 

There is no simple answer to these or similar questions, except to say that any amount of alcohol will affect a person's ability to drive to some degree.  It is true that the laws of nearly all States establish a BAC limit at which it is explicitly unlawful to operate a vehicle.  In those cases, that "limit" is 0.08 BAC.  But every State also makes it unlawful to drive when "under the influence" of alcohol, and the law admits the possibility that a particular person may be under the influence at much lower BACs.