Selective serotonin reuptake inhibitors
Selective serotonin reuptake inhibitors
Developed to treat depression with fewer adverse reactions, SSRIs, are chemically different from MAOIs and TCAs.
Some of the SSRIs currently available are:
- citalopram
- duloxetine
- escitalopram
- fluoxetine
- fluvoxamine
- paroxetine
- sertraline
- venlafaxine.
Pharmacokinetics
SSRIs are absorbed almost completely after oral administration and are highly protein-bound.
Safe and soundStopping SSRIs
Abruptly stopping selective serotonin reuptake inhibitor (SSRI) therapy may result in SSRI discontinuation syndrome, with dizziness, vertigo, ataxia, nausea, vomiting, muscle pains, fatigue, tremor, and headache. Psychological symptoms, such as anxiety, crying spells, irritability, feeling sad, memory problems, and vivid dreams, may also occur.
This syndrome is more common in SSRIs with a shorter half-life, such as paroxetine and venlafaxine, and occurs in up to one-third of patients receiving SSRI therapy.
Go slow
Tapering the dosage of the drug slowly over several weeks can prevent SSRI discontinuation syndrome. Fluoxetine is the least likely to cause this problem because of its extremely long half-life. The syndrome is self-limiting (over 2 to 3 weeks with treatment).
Pharmacodynamics
SSRIs inhibit the neuronal reuptake of the neurotransmitter serotonin.
Pharmacotherapeutics
SSRIs are used to treat the same major depressive episodes as TCAs and have the same degree of effectiveness. Fluvoxamine, fluoxetine, sertraline, and paroxetine are also used to treat obsessive-compulsive disorder. Fluoxetine has also been approved for the treatment of bulimia. Paroxetine is also indicated for social anxiety disorder.
Venlafaxine is an antidepressant drug that’s chemically different from other antidepressants and has unique properties in terms of absorption and mechanism of action. It has been particularly effective in patients with very severe depression.
Don’t panic, but there’s more…
SSRIs may also be useful in treating panic disorders, eating disorders, personality disorders, impulse control disorders, and anxiety disorders. Several SSRIs are approved for premenstrual (dysphoric) disorder.
Drug interactions
Drug interactions associated with SSRIs involve their ability to competitively inhibit a liver enzyme that’s responsible for oxidation of numerous drugs, including TCAs, carbamazepine, metoprolol,
flecainide, encainide, and antipsychotics, such as clozapine and thioridazine.
flecainide, encainide, and antipsychotics, such as clozapine and thioridazine.
Safe and soundRisks of antidepressants
Studies have shown a correlation between taking an antidepressant and the increased risk of suicidal behavior in young adults ages 18 to 24. Because of this risk, the FDA has mandated a black-box warning (the strongest warning possible) to be added to the labels of all antidepressants, warning practitioners to evaluate the need for the antidepressant with the increased risk it presents.
They don’t mix with MAOIs
The use of SSRIs with MAOIs can cause serious, potentially fatal reactions. Individual SSRIs also have their own particular interactions.
- Use of citalopram and paroxetine with warfarin may lead to increased bleeding.
- Carbamazepine may increase clearance of citalopram.
- Fluoxetine increases the half-life of diazepam and displaces highly protein-bound drugs, leading to toxicity.
- Fluvoxamine use with diltiazem hydrochloride may cause bradycardia.
- Paroxetine shouldn’t be used with tryptophan because this combination can cause headache, nausea, sweating, and dizziness.
- Paroxetine may increase procyclidine levels, causing increased anticholinergic effects.
- Cimetidine, phenobarbital, and phenytoin may reduce paroxetine metabolism by the liver, increasing the risk of toxicity.
- Paroxetine and sertraline may interact with other highly protein-bound drugs, causing adverse reactions to either drug.
Warning!Adverse reactions to SSRIs
Anxiety, insomnia, somnolence, palpitations, various rashes, and sexual dysfunction (anorgasmia and delayed ejaculation) may occur with the use of serotonin selective reuptake inhibitors (SSRIs).
Other reactions
Decreased plasma glucose levels can occur with fluoxetine. Orthostatic hypotension may occur with citalopram and paroxetine.
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