GSK ‘updated’ product information (PI) on Parnate
In the process of writing a few recent notes about Parnate (tranylcypromine) I tripped across the GSK updated product information about it, dated in 2016. Believe it or not, it still perpetuates all sorts of errors that should have been corrected long ago. I thought I would flag that and make a brief comment about it.
It is important for general readers to realise that these ‘PI’ documents can contain a lot of valuable information. But, any comments they make in relation to clinical usage are rarely helpful for clinicians. They are probably more directed towards medicolegal defensiveness and avoidance of any liability. Also, important facts and data sometimes seem to be ‘unaccountably’ omitted.
The first observation which surprised me was the information proffered that it was effective for psychotic depression.
Indeed, the very first line under the heading ‘Indications’ states this: ‘PARNATE® (tranylcypromine sulfate) has been used successfully to treat psychotic depressive …’.
Although I agree with this statement, I was astonished to see it in the GSK PI because it is my understanding, as explained in another commentary, that claim had been disallowed by the FDA long ago.
I would much like somebody to enlighten me concerning when this claim found its way back into the PI and also what it could possibly be based on. Informed readers may be aware that no trials involving psychotic depression have used Parnate since I started shaving more than 50 years ago. So what is the story?
The next thing to astonish me was that in describing its mechanism of action it completely fails to mention the fact that it elevates dopamine. This is quite extraordinary when one considers that it does this to a better and greater extent than any other drug that has been available for treatment in humans over the last 50 years. Why the reticence about discussing dopamine? Can it possibly be deficient knowledge alone?
There are still major errors and omissions in this new PI, including some in relation to explaining or elucidating the major interactions of serotonin toxicity and the tyramine pressor response. I can only imagine that the medical research department were out to lunch big time. Or maybe they just do not know about their own drug (believe me, that is quite likely).
If there is anybody out there has got contacts at GSK I would be fascinated to discuss some of these issues with who-ever is responsible for signing off on this document (mea culpa). They clearly need some expert advice – my fees are very reasonable!
The GSK PI can be found here: