Biological Theories
The diagnosis based on Kara presenting symptoms – among them fatigue, difficulty falling or staying asleep, unusual irritability, and disinterest in sexual activity – is major depressive disorder (MDD) (Shim et al., 2018). Biological theories of MDD include the neurobiological model focusing on dysregulation of the physical response to stress in the HPA axis and the immunological involvement hypothesis that implicates proinflammatory cytokines that trigger depressive symptoms.
Best Theory
The neurobiological model best explains the underlying dysregulated response to stress in MDD. The interconnected limbic-cortical pathways cause hormonal (cortisol) release due to exposure to a stressor, causing adaptive responses that are resolved within the HPA axis (Shim et al., 2018). However, in MDD, elevated cortisol secretion or hypercortisolism impairs the HPA structures, affecting emotional regulation, which means that individuals do not recover from stress.
Pharmacological Treatments
SSRIs such as fluoxetine, are effective first-line treatment for MDD. This class of medications includes many antidepressants with comparable effectiveness in treating this disorder. These drugs can be administered orally or parenterally in low doses. Another possible pharmacological treatment for MDD is a monoamine oxidase inhibitor, phenelzine (Shim et al., 2018). They are indicated for severe depressive symptoms that may not be improved with antidepressants.
Mechanism of Action
Fluoxetine causes an inhibitory effect on the brain synapses of MDD patients. It selectively blocks the reabsorption of serotonin, resulting in the accumulation of this neurochemical in the synapses (Shim et al., 2018). Phenelzine causes irreversible inhibition of monoamine oxidase enzyme, which increases norepinephrine and serotonin levels. Therefore, the drug produces long-lasting effects due to its impact on the concentration of neurochemicals in the synapses.
Possible Side Effects
Fluoxetine may cause vomiting, dry mouth, and hypersomnia in patients. However, according to Shim et al. (2018), insomnia can be prevented by taking the medication early in the morning. An adverse effect of fluoxetine is the potentially fatal serotonin syndrome when administered with serotonergic drugs. Key side effects of phenelzine are hypotension, dizziness, and sleepiness. Birth defects may also occur if the drug is taken during pregnancy.
Interactions and Contraindications
As an SSRI, fluoxetine interacts with serotonergic medications, including amphetamines. The drug-drug interaction causes a serious complication called serotonin syndrome and therefore, it is contraindicated in patients taking those drugs. Phenelzine interacts with tyramine, which leads to elevated blood pressure or stroke (Shim et al., 2018). The drug is contraindicated for people taking amphetamines, epinephrine, and common over-the-counter medications due to the possibility of adverse events.
References
Shim, H., Bahk, W. M., Woo, Y. S., & Yoon, B. H. (2018). Pharmacological treatment of major depressive episodes with mixed features: A systematic review. Clinical Psychopharmacology and Neuroscience, 16(4), 376-382. Web.