Posted by Scott L. Schofield on February 11, 2000, at 10:25:57
In reply to Re: Anybody respond to Nardil after failing Parnate?, posted by JohnL on February 11, 2000, at 7:48:38
A few years back, an investigation was performed by some of the fine folks at Mass General / Harvard comparing the efficacy of either adding lithium to 20mg of Prozac or raising the dose of Prozac to 60mg. Raising the Prozac to 60 mg/day brought about remissions in a significant number of those who had not responded to 20 mg/day. 80 mg /day is certainly a hefty dose, but I think it is unlikely to be dangerous if all applicable precautions are kept. I know that a dosage this high has been used before.The issue that JohnL has brought up regarding the interaction between Prozac and nortriptyline is important. The blood-levels of nortriptyline are elevated due to its "losing" to Prozac in the competition for enzyme sites that are responsible for the drugs' metabolic breakdowns. This has at least two negative consequences:
1. High levels of any tricyclic are dangerous because they can be cardiotoxic (harmful to heart function).
2. It is possible to take too much nortriptyline and lose the antidepressant effect. This drug is probably the most carefully studied of the tricyclics regarding dose/blood-levels versus antidepressant response. If blood-levels are too low, there is no response. If blood-levels are too high, there is no response. If blood-levels are kept within the upper and lower boundaries of the range of effectiveness (therapeutic window), an antidepressant effect can be achieved and maintained. 75mg of nortriptyline is about the average effective dose that seems to work for most people. If Prozac doubles or triples the blood-levels of nortriptyline as JohnL suggests, it is extremely likely that your blood-levels are way beyond the upper boundary of the therapeutic window.
Another very important issue concerns the washout period that must be adhered to when switching from Prozac to a MAO-inhibitor. One cannot mix MAOIs with SSRIs. It can cause a fatal reaction known as serotonin-syndrome.
The half-life (the time it takes to get rid of half of the drug present in the body) of Prozac, a SSRI, is about one week. The other SSRIs have half-lives of about one day. Therefore, blood-levels of Prozac remain significant for a much longer period of time. With the other SSRIs, the washout waiting period before beginning a MAOI is usually considered to be two weeks. Because of its much longer half-life, switching from Prozac to a MAOI requires a washout period of more like 5 - 8 weeks.
- Scott
poster:Scott L. Schofield
thread:20916
URL: http://www.dr-bob.org/babble/20000209/msgs/21137.html