Antitussive Preparations

Dextromethorphan (Romilar) is the dextroisomer of the methyl ether of levorphanol. Unlike its levorotatory congener, it possesses no significant analgesic property, exerts no depressant effects on respiration, and lacks addiction liability. It is an antitussive agent with a potency approximately one half that of codeine. 

Therapeutic doses of dextromethorphan (15 to 30 mg) produce little or no side effects, whereas excessively high doses (300 to 1500 mg) have been reported to produce a state resembling intoxication accompanied by euphoria. 

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Morphine and related opiates are known to suppress the cough reflex these compounds have thus been used extensively in antitussive preparations. Since this activity is not directly related to the analgesic potency, the ideal agent is one that has much reduced analgesic activity and thus, presumably, lower addiction potential. The weak analgesic codeine (4) is... 

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 narcotic antagonists are naltrexone and naloxone (Narcan). Dextromethorphan (Romilar) is used as an antitussive preparation. Apomorphine is used as an emetic agent. 

The amounts of these alkaloids in opium vary greatly with growing conditions and regions. Of the above, only noscapine and papaverine have no narcotic properties. Papaverine has found some medicinal use as an antispasmodic and cerebral vasodilator, and noscapine found use a few decades ago in antitussive preparations. 

Levoprome methotrimeprazine. levopropicillin propicillin, levopropylcillin potassium propicillin, levopropoxyphene [ban, inn) (levopropoxyphene napsylate [usan) Lilly 29866) is one of the methadone series, the (2/f,35)-(-)-form of propoxyphene. It is an OPIOID RECEPTOR AGONIST, but has very slight OPIOID ANALGESIC activity. It can be used in ANTITUSSIVE preparations, levopropoxyphene napsylate ... 

Benzonatate is a nonnarcotic antitussive preparation that reduces cough reflex by anesthetizing stretch receptors in respiratory passages. It is indicated (100 mg p.o. t.i.d.) in symptomatic relief of cough. 

Figure 13.10 Effect of the surfactant nature on the electropherograms of a complex antitussive preparation containing 14 solutes (analgesic, antitussive, antipyretic principles, conservatives and excipients). Buffer 0.02 M phosphate-borate, pH 9. Capillary 50 pm, 65 cm fused silica. Detection UV 210 nm. Adapted from [47].

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