Cough preparations

Miscellaneous Natural Products. The longhst of natural products used in early cough preparations has diminished to the point where only a few are still mentioned. Four natural products stiU used occasionally outside the United States ate squill, hotehound, cociEana, and ipecac. 

Ipecac is prepared from the dried roots and rhizomes of Cephaelis ipecacuanha (Brot.) A. Rich, and contains the alkaloids emetine [483-18-1] (17) and cephaeJine [483-17-0] (18) in a ratio between 2 1 and 4 1. It has been used extensively in cough preparations and is beheved to act by gastric reflex stimulation. Toxic effects include vomiting, irritation of the gastrointestinal tract, and cardiac arrhythmias (19). Ipecac symp is available over-the-counter in the United States only in 30-mL containers for use as an emetic in treating poisonings. 

Cold/cough preparations Alka-Seltzer Plus Formulations Cold (503) Day Cold (416) Cold Cough (416) Flu (387) Mucous Congestion (296) Night Cold (477). 

Codeine Phosphate The presence of aspirin along with codeine, even at a low moisture level, leads to acetylation of codeine phosphate in solid dose forms and is incompatible.36 Codeine sulfate solutions are more stable than phosphate salts.37 Drug dependence and withdrawal resemble that of opioid analgesics. Overdose causes acute intoxication in children, as accidental or deliberate ingestion of cough preparations containing codeine.38... 

In this situation, if the hydrogen ion concentration increases, the proportion of drug in the ionized form (the original condition) increases. Therefore, consequences of a shift in pH away from equilibrium conditions are opposite for weak acids and weak bases. For example, a solution of the weak base dextromethorphan (a drug present in cough preparations with a pfCa of 9.2) in the stomach (pH 1) will have approximately 1 of every 160,000,000 molecules in the unionized form. Obviously, gastric absorption will be significantly curtailed. 

A pharmacy-only medicine can be sold or supplied at a registered pharmacy under the supervision of a registered pharmacist without the need for a prescription from a medical practitioner. Examples of pharmacy-only medicine include cough preparations containing codeine, anti-diarrhoeal preparations containing atropine and diphenoxylate. 

There is no conclusive evidence either way on the efficacy of OTC cough preparations, but they are extremely popular. The placebo effect and reassurance derived from using them for self-limiting acute cough probably contribute significantly to their perceived effectiveness. 

Two classes of compounds - opioids and antihistamines - are used as antitussives in cough preparations. 

Side-effects include sedation, and anticholinergic effects such as dry mouth, urinary retention, constipation and blurring of vision. Both types of side-effect may be useful in cough preparations, aiding sleep if taken near to bedtime and drying up bronchial and nasal secretions. 

Because of side-effects, cough preparations containing antihistamines should not be recommended to patients with glaucoma or prostate problems and should be used with caution in older patients. 

Emetine (Fig. 7-9) in the form of the crude drug obtained from the roots and rhizomes of Ipecac (Cephaelis ipecacuanha) has been in use since the seventeenth century. The alkaloid, as the hydrochloride, has been used parenterally to treat amebic dysentery. It is also effective in hepatic infestation, but not against amebic cysts. Because of its cardiac toxicity and emetogenic properties, it has been superseded by metronidazole and chloroquine, but it is still used as an alternative. The amebicidal mechanism of emetine is protein synthesis inhibition by interference of peptidyl-RNA translocation. Since this action is general to eukaryotic cells, its relative selectivity in the presence of mammalian cells is not well understood. Unrelated uses of Ipecac (presumably due to its alkaloid content) are as an expectorant in cough preparations and an emergency emetic (Syrup of Ipecac). 

The anticholinergic effect of opiates (including OTC cough preparations containing dextromethorphan) would synergize with the actions of catecholamines produced by the MAOI. This could result in heart failure. 

Liquid medication takes one of three fonns elixirs, emulsion, and suspensions. An elixir is a sweet, pleasant-smelling solution of alcohol and water used as a vehicle for medicine. Robitussin, a commonly used cough preparation, is an elixir. An emulsion is a suspension of small globules of one liquid in a second liquid with which the first will not mix, such as milk fats in milk. And a suspension is a preparation of finely divided, undissolved particles dispersed in a liquid, such as bismuth subsalicylate (Pepto-Bismol). 

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