Antimuscarinic poisoning can result from the intake of excessive doses of belladonna alkaloids, synthetic an-timuscarinic drugs, and drugs from other pharmacolog-ical groups that have significant antimuscarinic activity (Table 13.2).
Signs of peripheral muscarinic blockade (e.g., speech disturbances, swallowing difficulties, cardioac-celeration, and pupillary dilation) are most common at lower doses, whereas CNS effects (e.g., headache, rest-lessness, ataxia, and hallucinations) are more apparent after large doses. Antimuscarinic drugs can produce atrial arrhythmias, A-V dissociation, and ventricular tachycardia and fibrillation. Many cases of antimus-carinic poisoning can be managed by removing unab- sorbed drug, treating symptoms, and providing support-ive therapy. However, any life-threatening effects (i.e., seizures, severe hypertension, hallucinations, or life-threatening arrhythmias) would justify the use of spe-cific antidotal therapy with the cholinesterase-inhibiting compound physostigmine. Special caution should be employed if the patient has any disorder that might be aggravated by the cholinergic stimulation resulting from the use of physostigmine.