Grapefruit: why this class is not the class that cares

Grapefruit: why this class is not the class that cares Writing it up because I had to work it out twice and would rather nobody else did.

I was wrong about grapefruit in a thread last spring and I would like to correct it publicly rather than quietly.

The error was in the units, which changed the conclusion by an order of magnitude. Setting out the corrected version, and the way I now check for that class of mistake.

On the opening post — agreed on the reasoning, with one qualification.

Speaking only to grapefruit as I have actually seen it, rather than as it is usually described: the effect is real, it is smaller than the thread suggests, and the variance between people is larger than the effect.

Confirming post #47 from a second method, which matters more than confirming it from a second person.

A supplement is a drug for interaction purposes, and the fact that it is sold without a prescription tells you nothing about whether it interacts. The paperwork is usually worse rather than better.

That much is documented. The rest is how I have interpreted it.

Answering the question post #48 raises rather than the one it answers.

I keep a log for grapefruit specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing and settled it.

A pharmacist can answer most questions in this subcategory in a few minutes with access to a proper interaction database, and that access is the thing a forum does not have.

This follows post #94 rather than contradicting it.

Anticoagulants: no direct interaction with the compounds in this class. Weight loss and body composition changes might affect the clearance or effect of warfarin if you are on it; monitoring INR more frequently during weight loss is reasonable.

The uncertainty is in the assumption, not in the calculation.

Where a published interaction study exists it usually reports an area-under-curve ratio, and that number is far more informative than a yes-or-no answer.

Agreed on all of that, and I have nothing to add to it.

What I would tell a new member reading about grapefruit for the first time: the confident posts are not the reliable ones, and the reliable ones are longer.