Final answer:
Tricyclic antidepressants are effective in treating major depression but come with a range of side effects including sleepiness, lowered blood pressure, weight gain, fatigue, and constipation. In normal subjects, they can increase feelings of unhappiness and anxiety. These drugs have a high toxic dose and can lead to severe irreversible effects and are nowadays less commonly prescribed due to their side effect profile.
Step-by-step explanation:
Tricyclic antidepressants, including drugs like imipramine and amitriptyline, are known for their efficacy in treating major depression. However, they exhibit a range of side effects, particularly when administered to individuals who are not suffering from depression. Normal subjects might experience sleepiness, lowered blood pressure, lightheadedness, unhappiness, and increased anxiety. Repeated doses can result in an exacerbated difficulty in concentrating and thinking.
Among patients with depression, a significant improvement in symptoms is often observed after two to three weeks of consistent use, which makes tricyclic antidepressants unsuitable for "as-needed" use. The side effects of these medications vary from person to person, with some of the most common being weight gain, fatigue, dizziness, loss of sexual desire, nausea, dry mouth, blurred vision, agitation, insomnia, and constipation. There can also be more severe and potentially irreversible side effects, such as insomnia, depression, and prostate enlargement. It's also important to note that these drugs inhibit the reuptake of neurotransmitters like serotonin and norepinephrine and are associated with a high toxic dose and the potential for fatal overdose.
Tricyclic antidepressants are less frequently prescribed nowadays due to their side effects and the availability of other antidepressants with more favorable safety profiles. Nevertheless, they may be more effective and have milder side effects in comparison to other treatment options, according to some studies which show they inhibit both serotonin and norepinephrine reuptake.