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Methotrexate is administered subcutaneously to Crohn's disease patients. There are very few studies evaluating the use of oral methotrexate in Crohn's disease. A drug and its pharmaceutical alternative are equivalent when the bioavailability of the alternative falls within 80–125% of the bioavailability of the standard US Food and Drug Administration - FDA.
Dr Wilson and colleagues from Canada compared the pharmacokinetic profiles of oral and subcutaneous methotrexate in Crohn's disease patients to determine the bioequivalence of these 2 routes.
The team reported that 11 patients received an oral, and a subcutaneous methotrexate dose separated by 1 week over a 2-week interval.  | | Relative oral bioavailability was 86% in comparison to subcutaneous | | Alimentary Pharmacology & Therapeutifcs |
The team of doctors collected blood samples at specified times over a 24-hour period for each patient on 2 separate days. Methotrexate plasma levels were obtained using sensitive mass spectrometry. The researchers found that the mean AUC values were 3375 ng/mL × h with oral methotrexate, and 3985 ng/mL × h with subcutaneous methotrexate. The team noted that mean AUC ratio (PO/SC) was 0.86. This correlates with a relative oral bioavailability of 86% in comparison to subcutaneous. The team observed no adverse events.
Dr Wilson's team commented, "The mean methotrexate area under the curve in these patients falls outside the 90% confidence interval for the bioequivalence limit." "Subcutaneous methotrexate is more bioavailable than oral methotrexate." "However, the mean relative methotrexate bioavailability nearly met the FDA bioequivalence standard, and oral methotrexate could be proposed in responders who would prefer this route."
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