Antidepressants - Tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs): Nursing pharmacology

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

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

In this video, we're going to cover two of the main classes of antidepressants, tricyclic antidepressants and monoamine oxidase inhibitors.

First, let's focus on tricyclic antidepressants, or TCAs for short, which can be further subdivided into tertiary or non-selective TCAs like amitriptyline, imipramine, and clomipramine, and secondary or selective TCAs such as desipramine and nortriptyline.

Now, tricyclic antidepressants are taken orally, and once absorbed into the bloodstream, they travel to the brain. Here, TCAs inhibit the reuptake of serotonin and norepinephrine.

As a result, their free levels within the synaptic cleft are increased right away. Although the effect of TCA's alleviating symptoms of depression is not evident for a few weeks.

Other indications for TCAs include phobic, panic, obsessive compulsive and anxiety disorders, neuropathic pain, as well as migraine prevention.

Now, even though TCAs are very effective in the treatment of depression, they can also act on other receptors, so they're not considered as the first line therapy due to their side effects.

Blockade of muscarinic receptors results in anticholinergic side effects such as dry mouth, blurred vision, tachycardia, urinary retention, and constipation.

On the other hand, blockade of alpha one adrenergic receptors may cause orthostatic hypotension. Whereas blockade of histamine receptors may result in sedation.

Moreover, TCAs may also block GABAA receptors, which normally send inhibitory neuronal signals. So by blocking these inhibitory signals, TCAs can result in a lower seizure threshold.

Additionally, tricyclic antidepressants can also cause serotonin syndrome, which usually occurs in clients who are treated with a combination of TCAs and other antidepressants that increase the level of serotonin in the brain.

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

TCAs can also inhibit cytochrome P450 enzymes in the liver. So when combined with other medications that are broken down and metabolized by these enzymes, TCAs will prevent their breakdown and cause them to build up in the body.

The most common cause of death in clients treated with TCAs include convulsions, coma, and cardiotoxicity, which involves arrhythmias and prolongation of QT interval.

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

As far as contraindications go, TCAs should be avoided in clients with heart disease and recent myocardial infarction. Also, TCA should not be administered within 14 days of monoamine oxidase inhibitors.

Speaking of monoamine oxidase inhibitors, or MAOIs for short, these include medications like isocarboxazide, phenelzine, and tranycyramine, which are taken orally, as well as selegiline, which can also be administered transdermally.

As their name implies, MAOIs work by inhibiting enzymes called monoamine oxidases, which are responsible for the breakdown of serotonin.

Norepinephrine And dopamine As a result, these neurotransmitters start to accumulate in the brain, eventually alleviating the symptoms of depression.

Besides major depressive disorder, some monoamine oxidase inhibitors can also be used to treat Parkinson's disease. Now, just like TCAs, one of the most dangerous side effects of MAOIs includes serotonin syndrome, which typically occurs when combined with other antidepressants that increase the level of serotonin in the brain.

Another dangerous side effect of MAOIs is hypertensive crisis, which is most commonly seen when combined with tyramine-rich food and drinks, such as cheese, red wine and beer, as well as foods containing phenylalanine, such as chocolate and caffeine.

Clients that develop hypertensive crisis typically present with hypertension, tachycardia, arrhythmias, as well as hyperthermia and agitation.

Finally, combining MAOIs with tryptophan may also cause neurological symptoms like confusion, agitation, amnesia, or delirium, as well as ataxia, myoclonus, hyperreflexia, and Babinski signs, where stimulating the lateral plantar aspect of the foot results in extension of the big toe.

Finally, MAOIs are contraindicated in clients with conditions like pheochromocytoma, cerebrovascular disease, and severe hepatic or renal impairment.

Now, before administering a TCA or MAOI obtain a baseline assessment of your client's depressive symptoms. Observe their behaviors and affect and ask them about changes in appetite, sleep patterns, and activities they enjoy.

If your client is prescribed a TCA review the results of their electrocardiogram or ECG to rule out pre-existing cardiac disease that could be exacerbated by TCAs.

If an MAOI is prescribed, check their current laboratory results for renal or hepatic insufficiency. Then ensure that your client understands the reason the medication is prescribed.

Stress the importance of taking the medication as prescribed and remind them that they should not stop taking their medication abruptly, even when they start feeling better.

Also, let them know it may take a few weeks before they start feeling the therapeutic effects of their medication. Next, teach your client how to manage side effects they may experience during therapy.

Both TCAs and MAOIs can cause orthostatic hypotension, which can increase their risk of falls. Instruct clients to make position changes slowly, especially if they experience symptoms such as lightheadedness or dizziness.

Now, if your client is prescribed a TCA help them manage the anticholinergic side effects. Suggest frequent sips of water or the use of sugar-free chewing gum or hard candy to help with a dry mouth.

Stress the importance of a diet rich in fiber and fluids, as well as keeping physically active to help prevent constipation.

To address urinary retention, advise your client to empty their bladder before taking their medication. To help with sedative effects, instruct your client to take their medication at night and remind them to avoid driving or other hazardous activities, especially during the first weeks of treatment.

If any of these symptoms become severe, remind your client to contact their healthcare provider. Lastly, arrange for your client to have a periodic ECG while being treated with a TCA.

If your client is prescribed an MAOI provide them a detailed list of foods they can eat, as well as foods to avoid that can interact with their medication, such as foods rich in tyramine, including aged cheese, smoked or fermented meats, and beer.

They should also avoid foods high in phenylalanine, like caffeinated beverages and chocolate, and foods high in tryptophan, such as eggs and turkey.

In addition, teach your client to recognize the symptoms of a hypertensive crisis and instruct them to seek medical attention right away if they experience any of these symptoms.

Now, during the first few weeks of treatment with a TCA or MAOI monitor your client closely for suicidal thinking. Explain that the healthcare provider will prescribe no more than a one week supply of the medication at a time during the first several weeks of treatment, and that initially they will be meeting with their healthcare provider on a regular basis.

As part of your ongoing assessment and monitoring, evaluate the effectiveness of treatment, improving or worsening depressive symptoms, as well as any signs of side effects or complications.

All right, as a quick recap, antidepressants are medications that are used to treat major depressive disorder. Two common classes of antidepressants are tricyclic antidepressants or TCAs, which work by inhibiting the reuptake of serotonin and norepinephrine, as well as monoamine oxidase inhibitors, or MAOIs, which work by inhibiting the breakdown of dopamine, serotonin, and norepinephrine.

Nursing considerations include client education and monitoring for the effectiveness of treatment and for side effects, especially suicidal thinking, most commonly in children, adolescents and young adults.