Sweating, antimuscarinic effects

Clinical features of overdose reflect the pharmacology of TCAs. Antimuscarinic effects result in warm, dry skin from vasodilatation and inhibition of sweating, blurred vision from paralysis of accommodation, pupillary dilatation and urinary retention. 

The antimuscarinic effects mainly include an elevation of heart-rate. Besides, a diminution in the production of bronchial, lachrymal, gastric, nasal, intestinal, sweat and saliva secretions are observed together with a reduction in intestinal motility. 

Significant side effects have been estimated to occur in about 5% of patients on TCAs, most of these effects being attributed to their antimuscarinic properties, for example, blurred vision, dry mouth, tachycardia and disturbed gastrointestinal and urinary tract function. Orthostatic hypotension due to the block of alphai adrenoceptors and sedation resulting from antihistaminic activity frequently occur at therapeutic doses, particularly in the elderly. Excessive sweating is also a fairly common phenomenon, but its precise mechanism is uncertain. In the elderly patient, the precipitation of prostatic hypertrophy and glaucoma by the TCAs is also a frequent cause of concern. 

Amitriptyline is a tricylic antidepressant and these have antimuscarinic side-effects, such as urinary retention, blurred vision, dry mouth and sweating. They also tend to cause drowsiness. 

Atropine suppresses thermoregulatory sweating. Sympathetic cholinergic fibers innervate eccrine sweat glands, and their muscarinic receptors are readily accessible to antimuscarinic drugs. In adults, body temperature is elevated by this effect only if large doses are administered, but in infants and children even ordinary doses may cause "atropine fever."... 

Q8 Acetylcholine is normally in balance with dopamine in the basal ganglia, but in Parkinson s disease dopamine levels are reduced and the effects of acetylcholine become more pronounced. To restore the balance, antimuscarinic agents are used to antagonize the excitatory actions of acetylcholine. They seem to be effective for tremor and reduce the secretion of saliva, digestive juices and sweat. 

Hyperhidrosis Astringents reduce sweat production, especially aluminium chloride hexahydrate (20%) in ethyl alcohol (95%).Antimuscarinics (topical or systemic) may help and high local concentrations can be obtained with iontophoresis. Minimally invasive sympathectomy is occasionally necessary complications include compensatory hyperhidrosis elsewhere.Temporary remission (16 weeks) is achieved by injection of boiulinum toxin, most effectively in the axilla. Treatment better in theory than in practice the volume of sweat dilutes the topical application the characteristic smell is produced by bacterial action, so cosmetic deodorants contain antibacterials rather chan substances that reduce sweat production. 

Antimuscarinic drugs are useful as adjunct therapy in Parkinson s, as they are useful in decreasing muscle rigidity and tremor, and attenuating the poverty of movement seen with the disease (e.g., bradykinesia). In addition, these drugs reduce undesirable effects of increased cholinergic activity, such as sweating and salivation. 

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