Antidepressants have five major classes that have distinguished mechanism of action. The first class is serotonin and noradrenaline reuptake inhibitors (SNRIs), which are employed to treat conditions such as depression and various mood disorders. They work by raising norepinephrine and serotonin levels, neurotransmitters in the brain which results in stabilized mood. Examples are duloxetine and desvenlafaxine (Agius & Bonnici, 2017). The other class is selective serotonin reuptake inhibitors (SSRIs), mainly used for depression treatment, and have lesser side effects than the other classes. They block the absorption or reuptake of serotonin in the brain, rendering it easier for the cells of the brain to receive as well as send messages, causing more stable and improved moods (Agius & Bonnici, 2017).
The consequent class is tricyclic antidepressants (TCAs). TCAs have three rings in their chemical structure, and work on five different pathways of neurotransmitter by blocking the reuptake of norepinephrine as well as serotonin in presynaptic terminals, causing increased concentration of the neurotransmitters in the synaptic cleft (Agius & Bonnici, 2017). They are commonly used to manage fibromyalgia, depression, and some types of anxiety. Monoamine oxidase inhibitors (MAOIs) are another class that work to inhibit monoamine oxidase action, a brain enzyme that assists in the break-down of neurotransmitters such as serotonin. When less serotonin is broken down, more serotonin will be in circulation, leading to less anxiety and more mood stabilization (Agius & Bonnici, 2017). The last class is noradrenaline and specific serotoninergic antidepressants (NASSAs). They have a dual mechanism of action, that increases the concentration of noradrenaline and 5-HT in the synaptic cleft to normal ranges (Agius & Bonnici, 2017).
Antidepressant medication overall effectiveness is equivalent within and between classes of medication. However, there are differences in each patient’s response to, as well as side effects yielded by individual agents and classes of medication. While issuing antidepressants, the following therapeutic protocols may be employed: Availability and costs. Family and patient’s response history to prior antidepressant medications (if any). Side effect profile. Patient preferences. Safety in overdose. Some antidepressant medications with anticholinergic side effects that may contribute to gingivitis, or xerostoma; thus such risks should be versed with patient prior to medication initiation. Drug-drug interactions. Negative or positive impacts on the patient’s comorbid medical or psychiatric conditions. These protocols apply throughout the lifespan.
Initiation of antidepressants should be coupled with teachings regarding adherence to medication and achievement of treatment goals. Medication should be continued for at least 6 to 12 months post adequate symptom response (Harmer, Duman & Cowen, 2017). Medication side effects often come before therapeutic benefit, and dwindle over time, thus side effects may be expected prior to symptom benefit. Symptom improvement is expected in two weeks, but for full response and remission, a longer length of time is required (Harmer, Duman & Cowen, 2017). Medication should not be ceased without guidance from the clinician. Since premature antidepressant treatment is associated with increased risk of relapse, medication should be taken as prescribed, even if symptoms wane.
In the administration of antidepressants, the decision should consider the safety factors of current health status, gender, age, genetic factors, culture, prescriptive authority, and ethical concerns. There are warning statements of antidepressants increasing the risk as compared to placebo of behavior (suicidality) and suicidal thinking in adolescents, young adults as well as children (Harmer, Duman & Cowen, 2017). In elderly patients, the risk of drug interactions and side effects is higher due to concomitant diseases, as well as decreased hepatic and renal function. There are some genetic differences concerning the metabolism of various medications, which can be ascertained by cytochrome P450, a form of genetic testing. The testing helps highlight patients prone to serious adverse reactions, or the presence of a narrow therapeutic window (Harmer, Duman & Cowen, 2017). These factors when incorporated into treatment aid in decision making, and establishing a route for treatment with the best results, and least side effects.
References
Agius, M., & Bonnici, H. (2017). Antidepressants in use in clinical practice. Psychiatr Danub, 29(Suppl 3), 667-671.
