Doctors Lounge - Hematology Answers
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Forum Name: Hematology Topics
|perryslc - Wed Jul 21, 2010 1:08 pm||
I'm currently taking Welbutrin (150mg 2X daily) , Lexapro (10mg 1X daily), and Xanax (up to 2mg daily). Could anyone of these drugs incerase the level of a BAC test result, and to what extent?
|Dr.M.Aroon kamath - Tue Aug 03, 2010 2:04 am||
A large number of medications have the potential to interact with alcohol.
Those interactions can alter the metabolism or activity of the medication and/or alcohol metabolism, resulting in potentially serious medical consequences.
When alcohol is ingested, a little of it is immediately metabolized in the stomach. The rest (major portion) is absorbed via the portal venous system primarily from the stomach and the upper small intestine. Alcohol absorption from the stomach is slow but rapid from the upper small intestine. The absorbed alcohol is then transported to the live. A part of the ingested alcohol gets metabolized during its initial passage through the liver- the “first-pass metabolism”. Only about 10% of the ingested alcohol undergoes the first pass metabolism. The remainder of alcohol leaves the liver intact and enters the systemic circulation and is distributed throughout widely to the tissues. If any “first pass metabolism” occurs in the gastric mucosa is controversial. Gastric alcohol dehydrogenase enzyme (ADH) has been demonstrated in the gastric mucosa. Some believe that this gastric first pass metabolism occurs significantly at low levels of alcohol consumption.
In the liver, alcohol is metabolized by several enzymes, the most important of which are ADH and cytochrome P450. The activities of these enzymes are highly variable, accounting for the observed variations in alcohol elimination rates among individuals.
Cytochrome P450 actually consists of two enzymes,
- cytochrome P450 reductase and
CYP2E1 plays a part in the metabolism of many drugs and therefore involved in many alcohol-medication interactions.
There are two types of alcohol-medication interactions:
- pharmacokinetic interactions, in which alcohol interferes
with the metabolism of the medication, and
- pharmacodynamic interactions, in which alcohol enhances the effects of certain medications, particularly in the central nervous system(such as, sedation).
Pharmacokinetic interactions generally occur in the liver, where both alcohol and many medications are metabolized, frequently by the same enzymes.
Histamine H2 receptor antagonists such as Nizatidine, Cimetidine, and Ranitidine inhibit ADH in the stomach, thereby reducing alcohol first-pass metabolism. They also increase gastric emptying, thereby allowing alcohol to enter the upper small intestine where, the absorption is very rapid. As a result, blood alcohol levels (BALs) are often higher than expected for a given alcohol dose. This effect tends to increase over time.
The following study was a double blind, placebo-controlled study involving nineteen healthy male subjects. This study evaluated the effects of escitalopram, given alone and when co-administered with alcohol, on cognitive and psychomotor function in those healthy subjects.
"Effects of Escitalopram Administered Alone and with Alcohol on Cognition and Psychomotor Performance"
Candace Jeavons Wilkinson, PhD et al, Southern California Research Institute, Los Angeles, CA; UCLA Mood Disorders Research Program
Presented at the 43rd Annual New Clinical Drug Evaluation Unit MeetingBoca Raton, Florida | May 27-30, 2003
This study concludes thus,
“An acute dose of escitalopram, compared to placebo, does not appear to cause any significant impairment for a wide variety of cognitive and psychomotor skills in healthy male subjects.
Co-administration of escitalopram with alcohol does not appear to potentiate alcohol-induced impairment of cognitive and psychomotor function”.
Benzodiazepines such as alprozolam which also act as gamma-aminobutyric acid (GABA) agonists, are known to cause blackouts as a result of high dose use. Isolated published reports involving small numbers of patients suggest that individuals who have borderline personality disorders, a prior history of violent or aggressive behavior, or alcohol or substance abuse may be at risk for such events. What might seem like one drink may be equivalent to a couple more when under the influence of a benzodiazepine drug.
Changes in pharmcodynamics and pharmacokinrtics of benzodiazepines have been reported in a variety of disease states including alcoholism, impaired hepatic function and impaired renal function.
Alprazolam concentrations may be reduced by up to 50% in smokers compared to non-smokers.
Maximal concentrations and half-life of alprazolam has been seen to be approximately 15% and 25% higher in Asians in comparison to Caucasians.
There is as yet no convincing evidence to implicate Escitalopram or alprazolam in causing high BACs.
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