Miscellaneous antidepressants
Other antidepressants
in use today include:
·
maprotiline and mirtazapine, tetracyclic antidepressants
·
bupropion, a dopamine reuptake blocking agent
·
venlafaxine, a serotonin-norepinephrine reuptake inhibitor
·
trazodone, a triazolopyridine agent
·
nefazodone, a phenylpiperazine agent.
The paths these antidepressants take through the
body may vary:
§ Maprotiline and mirtazapine are absorbed from
the GI tract, dis-tributed widely in the body, metabolized by the liver, and
excreted by the kidneys.
§ Bupropion is well absorbed from the GI tract
and metabolized by the liver. Its metabolites are excreted by the kidneys. It
appears to be highly bound to plasma proteins.
§ Venlafaxine is rapidly absorbed after oral
administration, par-tially bound to plasma proteins, metabolized in the liver,
and ex-creted in urine.
§ Trazodone is well absorbed from the GI tract,
distributed widely in the body, and metabolized by the liver. About 75% is
excreted in urine; the remainder is excreted in stool.
§ Nefazodone is rapidly and completely absorbed
but, because of extensive metabolism, only about 20% of the drug is available.
The drug is almost completely bound to plasma proteins and is excret-ed in
urine.
Much about how these drugs work has yet to be fully
understood:
·
Maprotiline and mirtazapine probably increase the amount of
norepinephrine, serotonin, or both in the CNS by blocking their reuptake by
presynaptic neurons (nerve terminals).
·
Bupropion was once
thought to inhibit the reuptake of the neu-rotransmitter dopamine; however, it
more likely acts on nonadren-ergic receptors.
·
Venlafaxine is thought
to potentiate neurotransmitter activity in the CNS by inhibiting the neural
reuptake of serotonin and norepi-nephrine.
·
Trazodone, although its
action is unknown, is thought to exert antidepressant effects by inhibiting the
reuptake of norepineph-rine and serotonin in the presynaptic neurons.
·
Nefazodone’s action
isn’t precisely defined. It inhibits neuronal uptake of serotonin and
norepinephrine. It’s also a serotonin an-tagonist, which explains its
effectiveness in treating anxiety.
These miscellaneous drugs are all used to treat
depression. Tra-zodone may also be effective in treating aggressive behavior
and panic disorder.
All of these antidepressants may have serious,
potentially fatal, ef-fects when combined with MAOIs. Each of these drugs also
car-ries its own specific risks when used with other drugs:
·
Maprotiline and mirtazapine interact with CNS depressants to cause an
additive effect.
·
Bupropion combined with levodopa, phenothiazines, or TCAs increases the
risk of adverse reactions, including seizures.
·
Trazodone may increase serum levels of digoxin and phenytoin. Its use
with antihypertensive agents may increase hypotensive ef-fects. CNS depression
may be enhanced if trazodone is adminis-tered with other CNS depressants.
·
Nefazodone may increase the digoxin level if administered with digoxin.
It increases CNS depression when combined with CNS depressants. (See Adverse reactions to miscellaneous
antidepres-sants.)
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