posted 11-13-2003 04:16 PM              

I had surgery about a month ago, and my doctor suddenly switched my prescription from Vicodin (5/500 tabs. 1-2 every four hours) to Darvocet-N (100/650 tabs. 1-2 every four hours). He did this without my knowledge, and was not aware that I started taking the Lexapro and the Trazodone. I'd like to know if there are any interactions between these three medications (Lexapro, Darvocet-N, and Trazodone) that I should be aware of? Are they safe to take together?

I have severe anxiety when it comes to taking medications, so any reassurance here would be appreciated.

posted 11-27-2003 11:06 PM              

1. "Pharmacokinetic" drug interaction:

Darvocet-N (Propoxyphene and Acetaminophen) can inhibit the metabolism (break down) of both Lexapro and trazodone leading to an increase in their blood levels and subsequent increase in their side effects. To explain, Darvocet-N is an inhibitor (antagonizes) the action of a specific liver enzyme CYP3A4) that both Lexapro and trazodone heavily depend on for their metabolism. This leads to the interaction I mentioned above.

The end result is that, you may experience more side effects from Lexapro (e.g., increased upset stomach, headache, diarrhea, anxiety, restlessness, agitation, tremor, etc.) and trazodone (e.g., increased drowsiness, dizziness, lightheadedness, drop in blood pressure, etc.).

2. "Pharmacodynamic" drug interaction:

This occurs when a drug that acts in one particular organ, is added to another that also acts on the same organ. For example, Lexapro and trazodone acts in the brain that may cause certain side effects such as drowsiness, dizziness, lightheadedness, fatigue. Darvocet-N can also act on the brain causing dizziness, lightheadedness, drowsiness, fatigue. (Sometimes, it may cause the opposite effect such as excitement and insomnia.)

In this case, based on the drug-interaction pathways described above, it is clinically prudent to use less dose of Lexapro and trazodone when combined with Darvocet-N to avoid increased in their side effects. You should also be warned of the potential for increase side effects and to avoid certain activities that require attention (e.g., driving, swimming, operating dangerous machinery, etc.) until you have adjusted accordingly to the side effects.

Incidentally, Vicodin (hydrocodone with acetaminophen) does not appear to interfere with the metabolism of Lexapro and trazodone. In short, it does not have a "pharmacokinetic" drug interaction with these drugs. However, there may still be a "pharmacodynamic" drug interaction with Vicodin, Lexapro and trazodone. Vicodin, being an opiate, may increase the effect of trazodone and Lexapro at the site of action (brain). This could lead to increase in drowsiness, dizziness, lightheadedness, and fatigue.