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Prozac is the best known of the SSRI antidepressants. It was the first
to be released in this country, and is still commonly prescribed. See the
general page on SSRI's for more information pertaining
to this class of antidepressants.
Prozac has several properties which distinguish it from other SSRI's.
Is is very activating, which makes it a good choice for people who have
very low energy. However, may be more likely to increase nervousness, insomnia,
and anxiety than some of the other medications in this class, especially
at higher dosages. Prozac is the best studied of the SSRI antidepressants
in pregnancy. While it has not been demonstrated to be entirely safe, its
use during pregnancy may be appropriate under certain conditions.
Prozac exerts its effects longer than any of the other SSRI antidepressants.
Prozac itself has a 2-3 day half-life in the system, and one of its active
metabolites, norfluoxitine, has a 7 or 8 day half-life. What this means is that once a person starts taking Prozac,
it takes about a month for it to build up the body, and once it is stopped,
it takes a month or two to completely eliminate it. This has both advantages and disadvantages.
The fact the medication builds up slowly may help to reduce early side effects
(although it is still often best to start Prozac at a low dosage). Its tendency
to be eliminated slowly means missing a day's dose has little effect, and
that dosage can be fine-tuned, for instance, by taking it two out of 3 days.
In addition, it may be less likely to cause the withrdawl symptoms we see
with other SSRI's if they are stopped abruptly. The main disadvantage of
this long half life is that, should the medication cause an undesireable
side effect, such as excessive activation, it can take a long time to get
it out of the system. The real clinical impact of this is debated, but most
psychiatrists would feel less comfortable prescribing Prozac than the other
SSRI's if there was a concern about the presence of bipolar illness or a
mixed affective disorder.
Another advantage of Prozac's long half life is that it appears less
likely to cause SSRI Discontinuation Syndrome.
In fact, sometimes one or two doses of Prozac can be used to eliminate the
side effects of stopping one of the other, shorter half-life SSRI antidepressants.
Specific Drug Interactions
As compared to the other SSRI's, Prozac is a particularly strong inhibitor
of one of the liver enzyme systems which breaks down other drugs (the cytochrome
P450 2D6 system). As a result, it may be more likely to interact with other
drugs than some of the other SSRI's, and adjustments in dosages may be necessary.
These include some tricyclic antidepressants, antipsychotics, certain cardiac
antiarrhythmics, Dilantin, Tegretol, some beta blockers, codine, and trazadone.
None of the SSRI's should not be combined with Seldane, Hisminal, and Propulsid.
Like all SSRI's, Prozac can cause the Serotonin
Syndrome if mixed with other agents which increase serotonin.
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1999 Deriddne Web Operations