Histamine receptor antagonists dosages

Many other therapeutic or non-therapeutic agents may produce CNS depression at some part of their dosage range. For instance, many antihistamines (histamine Hi-RECEPTOR antagonists), when used as antiallergic agents or in the treatment of motion sickness, may cause drowsiness or sleep, which can be a considerable disadvantage. In overdose, maiiy... 

The deliberate or accidental ingestion of natural belladonna alkaloids is a major cause of poisonings. Many histamine Hj-receptor antagonists, phenothiazines, and tricyclic antidepressants also block muscarinic receptors, and in sufficient dosage, produce syndromes that include features of atropine intoxication. 

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