Psychopharmacology
Which antidepressants cause no sexual dysfunction?
Bupropion, mirtazapine, and nefazodone. Duloxetine, a newer antidepressant, may have minimal sexual side effects as well.
What medication could psychiatrists use to treat patients with male sexual exhibitionism?
The first-line medication is medroxyprogesterone acetate.
Other medications including antidepressants and antipsychotics could also be used.
What receptor is related to mirtazapine’s sedation and weight gain side effects?
Histamine 1 receptor.
What is the important pregnancy-related factor that influences a patient’s lithium level?
Massive fluid shifts at the time of delivery.
Which atypical antipsychotic is unique by its inhibition of norepinephrine reuptake?
Ziprasidone.
Which atypical antipsychotics is a partial D2-receptor agonist?
Aripiprazole.
Which part of the brain is primarily involved in the synthesis of serotonin?
Raphe nuclei.
The cardiac effects of lithium most closely resemble which phenomenon on an electrocardiogram?
Hypokalemia.
What medication could significantly increase serum levels of paroxetine?
Cimetidine. It blocks the liver cytochrome P450 (CYP450) enzyme that metabolizes paroxetine.
What medication could significantly decrease the serum level of the medicine itself?
Carbamazepine. It induces the liver enzyme via an autoinduction mechanism to metabolize more medication.
What is the safety of antidepressants in pregnancy?
Because of the lack of convincing prospective data, this is not a fair question. Of note is that class B antidepressants have been found safe in animal studies, class C drugs have shown adverse effects in animal studies, and neither has established human safety. Because the vast majority of human studies have focused on SSRIs and tricyclic antidepressants (TCAs), these drugs are at least well tested. Therefore, SSRIs can be suggested for use during pregnancy, given their better side-effect profile (in pregnant women), with the exception of paroxetine.
Class B antidepressant maprotiline is the only one.
Class C antidepressants are SSRIs except paroxetine, MAOIs, bupropion, mirtazapine, and venlafaxine and all TCAs except those in class D named below.
Class D: Amitriptyline, imipramine, nortriptyline, and paroxetine.
Which antidepressants have adverse cardiac effects?
TCAs and trazodone.
Which antidepressants have strong sedative effects?
Amitriptyline, clomipramine, imipramine, mirtazapine, nefazodone, and trazodone.
Which antidepressants have weak or no anticholinergic effects?
SSRIs, bupropion, mirtazapine, nefazodone, trazodone, and venlafaxine. (TCAs and MAOIs have strong anticholinergic effects.)
What is the most frequent side effect of MAOIs?
Hypotension.
What is the treatment of choice for atypical depression?
MAOIs (phenelzine, tranylcypromine).
What are the contraindications to bupropion?
Seizure, eating disorders, and use of an MAOI within the previous 14 days.
Facts about MAOIs:
The most common side effect of MAOIs is orthostatic hypotension.
Foods that contain a high level of tyramine (e.g., red wine, aged cheese, nuts, chocolate) are contraindicated during the use of MAOIs.
MAOIs are contraindicated with the use of:
All other antidepressants. A 14-day (28-day for fluoxetine) systemic clearance period is necessary.
Meperidine.
Adrenergic agonists (e.g., phenylephrine, phenylpropanolamine).
Adrenergic antagonists such as phentolamine are not contraindicated with MAOIs.
Lithium is not contraindicated with MAOIs.
What is the clinical presentation of an MAOI-induced hypertensive crisis?
High blood pressure (BP), headache, stiff neck, and vomiting.
How should an MAOI-induced hypertensive crisis (BP = 240/140 mm Hg with a pounding headache) be treated?
The first-line treatment agent is an α-adrenergic blocking agent given intravenously (IV). Phentolamine (up to 5 mg IV) has been used.
Chlorpromazine (25 to 50 mg intramuscularly [IM] or orally [PO]) can be given as a second-line agent and is usually available.
Oral nifedipine can be given if there is early onset of a severe, bilateral, pounding occipital headache.
What is the pharmacologic mechanism of action of mirtazapine?
Central α2-adrenergic receptor antagonism. Since activation of α2-receptors inhibits the release of serotonin, mirtazapine can increase central serotonergic tone. In addition, mirtazapine blocks 5-hydroxytryptamine (serotonin) types
2 and 3 (5-HT2 and 5-HT3) receptors, and therefore increases the relative activity of 5-HT1a and 5-HT1c receptors.
2 and 3 (5-HT2 and 5-HT3) receptors, and therefore increases the relative activity of 5-HT1a and 5-HT1c receptors.
The sedative effect of mirtazapine is caused by its antagonistic effect at the histamine 1 (H1) receptor. The sedative effect appears at a low dose, but may weaken at a higher dose.
What are the side effects and drug interactions of nefazodone?
Has no anticholinergic effects. (The only antidepressants that have moderate to severe anticholinergic effects are TCAs and MAOIs.)
Does not cause sexual dysfunction.
Is highly sedative.
Is a strong inhibitor of CYP450 3A4. Only triazolam is officially contraindicated for concurrent use with nefazodone.
Benzodiazepines metabolized by CYP450 3A4 and therefore not recommended for concurrent use with nefazodone are: Midazolam, alprazolam, and triazolam (MAT). Diazepam is metabolized by both CYP450 3A4 and CYP450 2C19.
What are the characteristics of serotonin syndrome?
It is caused by SSRIs or MAOIs, especially when these are combined with tyramine-containing foods.
The combination of MAOIs with meperidine is contraindicated. A 14-day washout period should be allowed when switching from MAOIs to other antidepressants.
Features of the serotonin syndrome are:
Jitteriness, myoclonus, tremor at rest, hypertonicity, and rigidity.
Autonomic instability (diaphoresis, hypo-/hypertension).
Insomnia, excitement, coma, death.
What are the half-lives of various SSRIs?
Longest: Fluoxetine (7 to 15 days).
Shortest: Fluvoxamine (15 hours).
All other SSRIs: 1 day.
Fluoxetine is the only SSRI with clinically active metabolites (norfluoxetine).
What drug interactions occur with TCAs?
TCAs are metabolized by CYP450 2D6, 1A2, and 3A4.
Cigarette smoking, which induces CYP450 1A2, may decrease TCA concentrations.
Some antipsychotic agents (e.g., clozapine, haloperidol, risperidone, thioridazine) are competitors with TCAs for CYP450 2D6, and therefore increase TCA concentrations.
Methylphenidate decreases the metabolism of TCAs and therefore increases their concentrations.
Drugs that increase TCA levels are antipsychotics and methylphenidate.
Cigarette smoking decreases TCA levels.
What severe reactions have occurred with TCAs?
Cases of sudden death have been reported in children in association with the use of desipramine.
Overdosage with TCAs is associated with arrhythmia, seizure, delirium, and respiratory depression.
What is the best monitoring method to use for a patient who has overdosed on an unknown amount of a TCA?
Electrocardiography.
TCAs can potentially cause cardiac arrhythmia and death.
Which TCA has blood levels that are related to its clinical effect and needs to be monitored?
Nortriptyline.
The clinical therapeutic blood level for nortriptyline is 50 to 150 ng/mL.
What are the major effects and properties of venlafaxine?
Venlafaxine blocks reuptake of three neurotransmitters: Serotonin, norepinephrine, and dopamine.
It may cause increased diastolic BP.
Its half-life is very short among antidepressants (5 hours, and the half-life of its metabolite, desmethylvenlafaxine, 12 hours).
Venlafaxine does not inhibit CYP450.
What are the half-lives of various benzodiazepines?
Short (hours): Triazolam (Halcion), oxazepam (Serax). Benzodiazepines with short half-lives are associated with rebound insomnia when their use is discontinued.
Intermediate (<1 day): Alprazolam (Xanax), lorazepam (Ativan).
Long (>1 day): Clonazepam (Klonopin).
Very long (days): Diazepam (Valium), chlordiazepoxide (Librium).
What benzodiazepines are safe to use in patients with compromised hepatic function?
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