Selective Serotonin Reuptake Inhibitors

Selective serotonin reuptake inhibitors (SSRIs) are antidepressants that treat major depression and several other disorders. They are effective for clients who have been diagnosed with bipolar disorder, panic disorder, obsessive-compulsive disorder (also called OCD), premenstrual dysphoric disorder, and bulimia nervosa. As mentioned earlier, some SSRI medications, such as paroxetine, are effectively used to treat anxiety.

Prototype and Other Medications

Fluoxetine is the prototype medication for SSRIs. Other SSRIs include citalopram, escitalopram oxalate, paroxetine, and sertraline.

Expected Pharmacologic Action

SSRIs selectively block the reuptake of the neurotransmitter serotonin. This action strengthens the transmission of serotonin at the serotonergic synapses. The end result is a gradual adaptation of cells to changes that the blockade creates, which leads to a resolution of depressive and other psychogenic manifestations. SSRIs produce CNS excitation in contrast to the TCAs, which produce CNS depression.

Adverse Drug Reactions

SSRIs can cause many adverse effects, the most common of which are insomnia, nervousness, sexual dysfunction, and headache. Other concerns include weight gain, particularly with long-term therapy, and hyponatremia, especially in older adults and clients taking diuretics. SSRIs increase the secretion of the anti-diuretic hormone, also called ADH, causing increased excretion of sodium. As with other antidepressants, there is an increased risk for suicide, particularly in children and young adults.

Safety Alert

Serotonin syndrome, which occurs when there is too much serotonin in the body, can develop if the dose of an SSRI is too high or if clients concurrently take another medication or herb that also increases serotonin, such as an MAOI or St. John’s wort. Manifestations include mental confusion, difficulty concentrating, fever, agitation, anxiety, hallucinations, incoordination, hyperreflexia, diaphoresis, and tremors. The breakdown of muscle tissue that can result from the hyperreflexia can release toxins in the body and damage the kidneys.

Interventions

For clients taking an SSRI, monitor for insomnia and nervousness. A lower dosage might help resolve these manifestations. A lower dosage might also help clients reporting sexual dysfunction, but the prescriber might have to switch to another antidepressant for complete resolution of the problem. Monitor for headaches and document weight weekly throughout therapy. Evaluate clients for increases in depression and suicidal ideation, and initiate suicide precautions when appropriate.

Safety Alert

Clients taking diuretics and an SSRI are at increased risk for hyponatremia. Closely monitor serum sodium levels and watch for lethargy, abdominal cramps, diarrhea, and nausea. Untreated hyponatremia can result in seizures, coma, and even increased intracranial pressure from swelling of the brain.

Administration

SSRIs are available for oral use only. Generally, it takes 4 to 6 weeks to achieve clinical effectiveness. Taking an SSRI with food is a good option for clients who experience nausea or other gastrointestinal manifestations. These medications can cause insomnia, so it’s best to take them in the morning.

Client Instructions

When instructing clients about taking SSRIs, make sure they understand that they should report nervousness and insomnia. They should take the medication in the morning to avoid interference with sleep. They should also report impotence, decreased libido, and headache. For headache, they can try over-the-counter analgesics, such as acetaminophen. Clients should avoid ibuprofen due to the increased risk of gastrointestinal bleeding. It is also important that they eat a healthy diet and increase their exercise and activity levels. Advise them to report any manifestations of hyponatremia, such as lethargy, abdominal cramps, diarrhea, and nausea. Make sure they understand that these medications can increase the risk of suicide and that they should report any worsening of depression or thoughts of suicide. Finally, be sure they report manifestations of serotonin syndrome, including increased anxiety, fever, excessive sweating, tremors, and hallucinations. If they experience these, they should stop taking the medication and call their provider.

Contraindications and Precautions

Contraindications for SSRIs include clients who have a history of hypersensitivity to SSRIs and people taking MAOIs. Children less than 7 years of age should not take fluoxetine. Use them with caution for older adults and for clients who have liver disease, peptic ulcer disease, or diabetes mellitus. SSRIs may decrease glucose control in clients who have diabetes mellitus. They may need to adjust the dosage of their antidiabetic medications. Also, use SSRIs with caution in clients with hyponatremia, existing cardiac disease, or a history of suicidal tendencies.

Interactions

Taking an SSRI within 2 weeks of MAOIs or another SSRI increases the risk of serotonin syndrome. Fluoxetine increases the levels of tricyclic antidepressants and lithium. NSAIDs increase the risk of gastrointestinal bleeding.