Abstract

TORRES, L.M. et al. Effects of the interchangeability of transdermal fentanyl products. Rev. Soc. Esp. Dolor [online]. 2009, vol.16, n.1, pp.21-28. ISSN 1134-8046.

Introduction: the use of generic drugs is becoming increasingly widespread, a practice mainly aimed at controlling health expenditure. Because generic drugs are bioequivalent with the original make, these products are generally interchangeable. Nevertheless, drugs with a narrow therapeutic margin are exceptions to this rule. In the case of potent opioids, and specifically, of transdermal fentanyl, the interchangeability of the initial prescription by other physicians or by pharmacists is questionable, since substitution could result in a change in analgesia or in the development of adverse effects, compromising the safety of the drug in individual patients. Material and methods: we reviewed the reports received in our pain unit of patients previously controlled with a specific brand of fentanyl (Durogesic^® in all patients) who were switched to another brand of transdermal fentanyl by a physician other than the physician initially prescribing the drug or in the pharmacy. Results: in a 2-month period, we received 20 reports of loss of analgesic effect or of the presence of adverse effects, which were absent under Durogensic^® treatment, after switching this brand for a generic transdermal fentanyl product. Conclusion: irrespective of the policy of generic drug use and given the potency of fentanyl and the possible changes in plasma concentration when one brand is changed to another, we believe that, to maintain analgesic effect and avoid the development of adverse effects, any change should be authorized by the physician originally prescribing the drug or by the physician responsible for the patient's care.

Keywords : Opioids; Fentanyl; Interchangeability; Adverse effects.

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