(From Baby Katzung and lecture, 11 Mar 2001, by Brian Buschman)
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Tricyclic antidepressants block the reuptake of NE and 5-HT and some think this causes antidepressant effects. They take about two weeks to take effect during which time the NE receptor density changes. That only elevates the mood of depressed and has no effect on normal individuals.
Tricyclics are used for antidepressants but imipramine is used for bed wetting also. Others include amitriptyline, amoxapine, maprotiline and other “ines.”
Adverse effects of tricyclics are the result of excess NE (anti-muscarinic) effects including:
1) Orthostatic hypotension (a-blocker effect)
2) CV over stimulation
3) Blurred vision
4) Xerostomia
5) Constipation
SSRIs block just the 5-HT reuptake channels rather than 5-HT and NE and anti-a effects of the tricyclics. This gives SSRIs fewer anticholinergic effects and makes it more popular among the general physician.
Fluoxetine is used for treatment of major depression, OCD, bulimia, anorexia, PMS and pain with diabetic neuropathy.
It has a very long t ½ (up to 1 month) and it inhibits cyt P-450 therefore causing increased effects of other drugs (Barbs induce P-450).
OD does not cause arrhythmia but can cause seizures.
Other SSRIs include:
1) Fluvoxamine
2) Paroxetine
3) Sertraline
MAOIs block MAO all over the body, both in nerves and in the GI. In the GI MAO degrades tyramine so pts on MAOIs must avoid tyramine rich foods like aged cheese, chicken, liver, beer and red wines. Tyramine can cause catacholamine release.
MAOIs are used for depression in patients unresponsive to tricyclics and SSRIs, phobic states and for atypical depression.
MAOIs include:
1) Isocarboxazid
2) Phenelzine
3) Tranylcaypromine
MAOIs and SSRTs have a low potential for anticholinergic effects. MAOIs cause orthostatic hypotension.
MAOIs and SSRIs when given together cause seretonin toxicity so you must wait at least 6 weeks after stopping one to give the other.
Lithium is used in the treatment of bipolar disorder and in other mood disorders.
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