Pyrantel interactions

An interaction of pyrantel with theophylline has been reported (3). 

Hecht L, Mssurray WE. TheophyUine-pyrantel pamoate interaction. DICP 1989 23(3) 258. 

Figure 6. Iontophoretic application of acetylcholine (Ach) and pyrantel (a) Comparison of inward currents (upper trace) generated by the iontophoresis of Ach and pyrantel from a double-barrelled micropipette, b) Interaction of Ach and pyrantel showing reversible block of Ach currents following pyrantel application. The micropipette was placed within a distance of 50 urn from the bag membrane. Ejection currents of 250 nA for 1s were used. Vertical calibration 20 nA, membrane current. 400 nA, iontophoretic current (lower traces). (Adapted with permission from Ref. 2 Copyright 1985, Society of Chemical Industry).

Not understood. One suggestion is that the pyrantel inhibited the liver enzymes concerned with the metabolism of the theophylline, thereby increasing its levels. However, this is unlikely as the interaction occurred so rapidly. Another suggestion was that pyrantel may have increased drug release from the sustained-release theophylline preparation. 

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