Antidepressants - SSRIs and SNRIs: Nursing pharmacology

Antidepressants are medications primarily used to treat major depressive disorder, which is a condition associated with a persistent feeling of sadness and loss of interest in everyday activities.

Even though the exact cause of major depressive disorder is still unknown, there's some evidence that suggests that it’s related to low levels of neurotransmitters called monoamines, which include serotonin, norepinephrine, and dopamine.

In this video, we’re going to cover two of the main classes of antidepressants: selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors.

First, let’s focus on selective serotonin reuptake inhibitors, or SSRIs for short, such as fluoxetine, fluvoxamine, sertraline, paroxetine, citalopram, and escitalopram.

SSRIs are taken orally, and once absorbed into the bloodstream, they travel to the brain. Here, SSRIs inhibit the reuptake of serotonin.

As a result, free levels of serotonin within the synaptic cleft are increased right away, although the effect of SSRIs alleviating symptoms of depression are not evident for a few weeks.

Other indications for SSRIs include anxiety disorders like obsessive-compulsive disorder, or OCD; post traumatic stress disorder, or PTSD; panic disorder and phobias; as well as eating disorders like bulimia.

On the other hand, serotonin-norepinephrine reuptake inhibitors, or SNRIs, include duloxetine, venlafaxine, desvenlafaxine, and levomilnacipran.

SNRIs are also taken orally, and once they reach the brain, they inhibit the reuptake of both serotonin and norepinephrine, increasing their levels in the synaptic cleft.

Other indications for SNRIs besides major depressive disorder include generalized anxiety disorder and neuropathic pain.

Now, the brain has different types of serotonin receptors besides the ones involved in depression. Some of them mediate functions like mood, sleep, appetite, or sexual function.

So, some side effects of SSRIs and SNRIs include anxiety or nervousness, agitation, insomnia or drowsiness, loss of appetite, and sexual dysfunction.

Other side effects include headache, dizziness, sweating, and hyponatremia, as well as bruxism, dry mouth, nausea, vomiting, and diarrhea.

Additionally, SSRIs and SNRIs can also cause serotonin syndrome, which usually occurs when these medications are combined with other antidepressants that increase the level of serotonin in the brain, especially monoamine oxidase inhibitors, or MAOIs for short.

Clients that develop serotonin syndrome typically present with skin flushing, hyperthermia, agitation, muscle rigidity, seizures, and altered mental status or even coma.

Now, SNRIs also increase the levels of norepinephrine, so they can cause side effects like hypertension and tachycardia, as well as closed-angle glaucoma, and urinary retention.

Finally, an important boxed warning for all antidepressants is that they may increase the risk of suicidal thinking in children, adolescents, and young adults.