SSRI-Crusaders : Message: MHRA's position about the irreversible inactivation of CYP2D6

SSRI-Crusaders : Message: MHRA's position about the irreversible inactivation of CYP2D6


MHRA's position about the irreversible inactivation of CYP2D6 I think it would be helpful if I explain further the circumstances under which the studies by Concept Pharmaceutical Inc were conducted and how this translates to the situation in humans. The studies conducted by this company were in vitro studies (ie test tube studies). They looked at the direct effect of paroxetine on the CYP2D6 enzyme in cells that had been isolated from a liver, most likely an animal liver. The effect of certain medicines on these cells can indeed be to inhibit or even to inactivate the CYP2D6 enzyme.




In real life, when an individual takes a medicine it can inhibit or inactivate the CYP2D6 enzyme in the cells of the liver in the same way. This inhibitory effect will depend on many factors including the amount of a medicine circulating in the body. However, the effect is only on those cells and enzymes actually exposed to the medicine: as we are all continuously replacing the numerous cells, enzymes and proteins in our body any inhibitory effect will only last as long as sufficient levels of the medicine are circulating in the body.



I hope this clarifies our position on this issue.



Yours sincerely



Simon Gregor



Director of Communications







extracted from -



Via email



15 October 2009



Dear Mr Bryce



Ref: FOI request on irreversible inactivation of P450 2D6 (CYP2D6) enzyme activity



Thank you for your email of 21 September regarding your FOI request