Common cold cough preparations

The opioid derivatives most commonly used as antitussives are dextromethorphan, codeine, levopropoxyphene, and noscapine (levopropoxyphene and noscapine are not available in the USA). They should be used with caution in patients taking monoamine oxidase inhibitors (see Table 31-5). Antitussive preparations usually also contain expectorants to thin and liquefy respiratory secretions. Importantly, due to increasing reports of death in young children taking dextromethorphan in formulations of over-the-counter "cold/cough" medications, its use in children less than 6 years of age has been banned by the FDA. Moreover, due to variations in the metabolism of codeine, its use for any purpose in young children is being reconsidered. 

The prototype antihistamine of this group is diphenhydramine. It has antimuscarinic and pronounced central sedative properties and also an antitussive effect. The mechanism of the latter is unclear, but diphenhydramine is a common ingredient of propriety preparations for the treatment of coughs and colds. It is an effective anti-emetic, especially useful for prevention and treatment of motion sickness. Because of its anticholinergic properties it is occasionally used in the treatment of mild forms of Parkinson s disease. It is also of use in the treatment of drug-induced extrapyramidal effects. Piperazine derivatives... 

Ethanol has been used widely as a beverage, a medicinal, and a solvent in numerous pharmaceutical preparations. Such common usage often overshadows the fact that ethanol is a toxic substance. Ethanol consumption is associated with a variety of long-term effects, including cirrhosis of the Uver, death of brain cells, and alcoholism. Alcohol consumed by the mother can even affect the normal development of her unborn child and result in fetal alcohol syndrome. For these reasons, over-the-counter cough and cold medications that were once prepared in ethanol are now manufactured in alcohol-free form. 

The interaction between the MAOIs and oral phenylephrine is established, serious and potentially life-threatening. Phenylephrine commonly occurs in oral non-prescription cough, cold and influenza preparations, so patients should be strongly warned about them. Whether the effects of nasal drops and sprays and eye drops are also enhanced is uncertain, but it would be prudent to avoid them until they have been shown to be safe. The response to parenteral administration is also approximately doubled, so that a dosage reduction is necessary. 

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