This medication is the first rationally made psychiatric drug. The approach behind the development of this type of rational drug is to devise an innovative medication that is competent of affecting a particular neural spot of action while evading the effects on other action sites.
The purpose of such innovation is to create agents that are more safe and efficacious than other drugs. On the other hand, Monoamine Oxidase is a particular enzyme that is established in various parts of the body. Inside the brain tissues, Monoamine Oxidase annihilates neurotransmitters like Serotonin and Norepinephrine. They block its breakdown. This medication can be preferably used for managing dysthymia than tricyclics.
SSRIs are regarded as the first-line drug for depression. Physicians usually prescribe these drugs more frequently for elderly patients than other antidepressants. This drug is not a controlled medication. Among these types of drugs there are more similarities than disparities.
Even though each and every one of these drugs have an identical mechanism of action, each drug has vaguely diverse pharmacokinetics and pharmacological characteristics. In contrast with the aforementioned antidepressant, an MAOI is the least prescribed drug because of its dietary restrictions.
When considering patient characteristics and safety, TCAs are contraindicated in some specific cardiac conditions such as patients with a history of arrhythmias, sinus node dysfunction, or conduction defects. Caution is advised with the elderly, as they are more sensitive to cholinergic blockade as well as orthostatic hypotension.
Furthermore, individuals also suffering from dementia will be particularly susceptible to the toxic effects of muscarinic blockade on memory and attention span and would generally do best if given antidepressants with the lowest degree of anticholinergic effects. Finally, caution should be exercised when considering starting TCAs in patients with suicidal thoughts due to high lethality risks with overdose. The lethal dose is only eight times the therapeutic dose, so if TCAs are ingested in an overdose, they may block the sinoatrial node in the heart.
Aside from selegiline, which is a selective MAO B inhibitor, all other agents inhibit both MAO A and B enzymes responsible for serotonin, norepinephrine, and dopamine metabolism in the brain. Due to severe adverse effects and required diet restrictions, MAOIs are generally reserved for patients who have failed other antidepressants. Hypertensive crisis can occur when patients taking MAOIs ingest foods containing tyramine, such as beer, wine, aged cheese, and smoked meat.
This reaction presents as an acute onset of severe headache, nausea, neck stiffness, heart palpitations, chest pain, and confusion. MAOIs can also cause serotonin syndrome.
If fluoxetine is the SSRI, which has a long half-life, the washout period should be 5 weeks. Due to the high rate of drug interactions with these agents, caution should be used when prescribed to patients with asthma using sympathomimetic bronchodilators. In patients with hypertension, MAOIs may induce orthostatic hypotension, especially with concurrent diuretic treatments. These medications are safer than TCAs, and their adverse effects are similar to those of SSRIs, including nausea, vomiting, and sexual dysfunction, as well as elevated blood pressure.
Duloxetine has more norepinephrine activity than both of the aforementioned agents, thus being useful with physical symptoms such as muscle aches, headaches, stomach issues, and generalized pain, often occurring with severely depressed patients. Due to its effectiveness in pain symptoms, duloxetine has also been approved for other indications such as fibromyalgia and diabetic peripheral neuropathic pain.
Other Antidepressants 4,10 : Several other antidepressants are available that differ in their mechanism of action from the classes of medications described previously. Their adverse effects are similar to those of SSRIs, with minimal serotonin effects such as nausea and weight gain and little or no sexual dysfunction. Finally, there are three more antidepressants with mixed action available: mirtazapine, nefazodone, and trazodone TABLE 5.
All three agents block different serotonin receptors, thus having distinct effects. Mirtazapine causes more weight gain by increasing appetite. Nefazodone has limited uses because of hepatotoxicity and CYP3A4 enzyme inhibition, which leads to drug interactions. Trazodone blocks serotonin receptors to a great extent, with poor binding to muscarinic receptors.
Adverse effects such as sedation, headache, memory impairment, dry mouth, and constipation may occur. Caution is also advised with trazodone use in men due to risk of priapism. In general, antidepressant medications have been shown to be equally efficacious; therefore, medication choice should be based on adverse effects, drug interactions, safety, and patient preferences.
On the contrary, if patients do not respond or cannot tolerate the drug, switching to an alternative agent is also appropriate, taking into consideration that therapeutic effects will usually occur between 4 to 6 weeks, even though adverse effects might appear after 1 week of treatment. Given the difficulty in predicting what medication will be both efficacious for and tolerated by an individual patient, familiarity with a broad spectrum of antidepressants is prudent and useful.
Selective serotonin reuptake inhibitors: meta-analysis of efficacy and acceptability. SSRIs versus other antidepressants for depressive disorder. Cochrane Database Syst Rev. Selecting among second-step antidepressant medication monotherapies: predictive value of clinical, demographic, or first-step treatment features.
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