Tricyclic antidepressants anticholinergic activity

Many tricyclic tranquilizers and antidepressants exhibit some measure of anticholinergic activity. 

Bupropion is an a-aminoketone that is structurally related to amphetamines, and it exhibits unique activity comparable to that of other antidepressants. It is believed that bupropion restores the total amount of norepinephrine in the body. This compound is a poor reuptake inhibitor of dopamine, and does not exhibit anticholinergic activity or inhibit MAO. Its efficacy as an antidepressant is comparable to that of tricyclic antidepressants, and as a serotonin uptake inhibitor it is comparable to fluoxetine. It is preferable to use amoxapine. Synonyms of bupropion are amphebutamon and wellbutrin. 

Agents from this class of antidepressants are selective blockers of the re-uptake of serotonin at presynaptic neurones and have little if any effects on muscarinic, histaminergic, adrenergic or serotonergic receptors. They are as effective as the tricyclic antidepressants in the management of depressive disorders, but have less cardiovascular effects. They have less anticholinergic activity and because of their lower risk of cardiotoxicity in overdose they... 

Mechanism of Action A tricyclic antidepressant that blocks the reuptake of neu-retransmitters, including norepinephrine and serotonin, at presynaptic membranes, thus increasing their availability at postsynaptic receptor sites. Also has strong anticholinergic activity. Therapeutic Effect Relieves depression. 

Several organs are the target for the anticholinergic (anti-muscarinic) activity of the tricyclic antidepressants. They constitute the most common and troublesome adverse effects of the tricyclic antidepressants, but the peripheral anticholinergic actions can also be put to therapeutic use in conditions such as irritable bowel syndrome, premature ejaculation, and nocturnal enuresis. 

The tricyclic antidepressants increase bladder sphincter tone and the volume of fluid necessary to trigger detrusor contraction (80). Such effects may account for their efficacy in nocturnal enuresis, in which the benefit occurs early and at a low dosage, consistent with anticholinergic activity. However, this pharmacological action can cause hesitancy and urinary retention, especially in predisposed men who have prostatic hyperplasia. 

Mild anticholinergic activity (less than some other tricyclic antidepressants) could possibly lead to sedative effects, dry mouth, constipation, and blurred vision... 

Some systemic agents may possess sufficient anticholinergic activity to produce mydriasis and a weak cycloplegic effect.These medications include antimuscarinic drugs, antihistamines, phenothiazines, and tricyclic antidepressants (Table 35-9). 

Of the systemic antihistamines, the ethanolamines, including diphenhydramine, have significant antimuscarinic activity. In addition, the antipsychotic agents, particularly the phenothiazines such as thioridazine (Mellaril), have well-dociunented anticholinergic properties. Therapeutic doses of tricyclic antidepressants, like amitriptyline hydrochloride (Elavil) and imipramine (Tofranil), produce significant anticholinergic actions and thus have the potential for ocular side effects. 

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