Is it safe for a prostate cancer patient to use CBD/THC along with Viagra?

"I have researched the issue of CYP3A4 with CBD and Viagra. It seems a scary and risky mix. The surgeon wants him on the Viagra immediately for pre and post surgery. We have him on CBD/THC to try to shrink the tumor pre-op because it’s grown outside the capsule and into the nerve bundle on one side. I’m torn as to whether I must risk my husband’s cardiac health to save his sexual function!"


Hello and thank you for the great question.

I believe you are referencing the fact that Viagra and CBD are both metabolized in the liver, mainly via the enzyme CYP3A4; and since CBD has been shown to markedly inhibit that enzyme, you are concerned of a Viagra overdose which might lead to a cardiac event.

Honestly, this is a very difficult question to answer with absolute certainty since there are no studies evaluating the metabolism of both Viagra and CBD in vivo. Therefore, it is, for all intents and purposes, impossible to calculate a dosage change based on the inhibition of CBD on CYP3A4.

However, Viagra is considered safe for men, even with heart disease that does not limit physical exercise.

"It seems more likely that the [heart attacks and pain] reported with [Viagra] are related more to the performance of sexual activity in a patient with coronary artery disease than the use of the drug," notes Thomas H. Marwick, MD, PhD. Marwick is a heart disease researcher at the University of Queensland in Brisbane, Australia. The Arruda-Olson study, and Marwick’s accompanying editorial, appear in the Feb. 13 issue of TheJournal of the American Medical Association."

The main side effect of Viagra is what is called priapism – which is a very prolonged erection that can lead to permanent ED due to penile vascular damage. As has been said during all the ED pill commercials, go to the emergency room if the erection lasts longer than four hours; this risk (might) be heightened if the metabolism of Viagra is appreciably inhibited.

Please express your concerns with your husband’s urologist. Please do not take the above as medical advice as I have neither examined your husband, nor do I know of his complete medical history.

I hope this has been helpful.
Truly,
Richard Kim MD

drkim

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