THINGS YOU SHOULD KNOW ABOUT ANTI-DEPRESSANTS
Things you should know about ANTI_DEPRESSANTS
Depression is a very common clinical condition. it is associated with the feeling of sadness, loss of interest, self neglect, anorexia, sleep disturbances, suicidal feeling in severe cases etc.
various hypothesis have been proposed for pathogenesis of depression:
- decrease in levels or function of monoamines in cortical and limbic system.
- decrease in brain derived neurotrophic factor
- abnormalities in HPA axis, thyroid function and sex steroids level.
Antidepressants are drugs which can elevate mood in depression illness. practically, all antidepressants affect monoaminergic, transmission in the brain in one way or the other and many of them have other associated properties.
- tricyclic antidepressants : amitriptyline, amoxapine, doxepine, trimipramine, imipramine, clopmipramine
- selective serotonin reuptake inhibitors :fluoxentine, fluvoxamine, citalopram, sertaline, paroxetine.
- atypical antidepressants: trazodone, bupropion, , mirtazapine, venlafaxine,
- MAO-A inhibitors: moclobemide, clorgyline.
tricyclic antidepressants are well absorbed through the GI tract and are highly bound to plasma proteins. they are widely distributed in tissue including CNS. they are metabolized in liver. some of them like imipramine, amitriptyline etc produce active metabolite which are responsible for the long duration of action of these drugs.
Adverse effects and contradictions of tricyclic antidepressants:
- atropine like side effects : dryness of mouth, blurring of vision, constipation, urinary retention
- alpha-1 adrenergic blocking effects: postural hypotension, tachycardia, cardiac arrhythmias ,
- H-1 blocking effects: sedation and confusion
- other effects: increased appetite, weight gain, and may precipitate convulsions.
mechanism of action of antidepressants
mechanism of action of tricyclic antidepressants
MAO is a mitochondrial enzyme involved in the metabolism of biogenic amines. there are two isoforms of MAO . MAO is responsible mainly for the metabolism of NA 5-HT and tyramine. MAO-B selective for dopamine metabolism.
a selective and reversible inhibitor of MAO-A is relatively free of food and drug intereactions. hence,cheese reaction is rare. it is also devoid of anticholinergic , alpha-1 adrenergic blocking and sedative effects.
- tricyclic antidepressants involves hypertensive crisis, hyperpyrexia, convulsions, coma
serotonin syndrome: concomitant adminsitration of SSRIs with MAO inhibitors produce severe undesirable effects like tremor, restlessness, muscle rigidity, hyperthermia, sweating, seziures, coma due to increased serotonin levels at the synapse which is termed srotonin syndrome.
- SSRIs inhibit metabolism of a number of drugs such as antipsychotics, beta blockers , phenytonin etc can increase their plasma levels.
USES OF ANTI DERPRESSANTS:
- depression: antidepressants are used in the treatment of bipolar illness. it is better tolerability, less side effects .
- panic disorders
- obsessive compulsive disorders
- nocturnal enuresis
- atopic dermatitis.