In Reply.—Fazio's letter raises some interesting questions regarding possible drug interactions with caffeine and other substances. The elimination half-life of caffeine may be prolonged if administered together with cimetidine or an oral contraceptive medication. However, the increase in plasma caffeine levels would probably not be sufficient to warrant special concern regarding possible adverse cardiovascular effects. Furthermore, oral contraceptive pills are generally prescribed to young, healthy women, and blood pressure is routinely followed up because oral contraceptives by themselves can cause hypertension. However, there is no evidence that caffeine contributes to any increase in blood pressure in these patients.
Fazio is correct in drawing attention to the combined use of caffeine-containing over-the-counter medications with the ingestion of caffeine in the form of beverages. Stimulants with caffeine as the main ingredient could have a substantial effect on plasma caffeine concentrations, and users of these products should be aware of this possible
MYERS MG. Caffeine, Oral Contraceptives, and Over-the-Counter Drugs-Reply. Arch Intern Med. 1989;149(5):1222. doi:10.1001/archinte.1989.00390050163040
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