CIALIS help
 

been usin Viagra and decided to try Cialis. Just got my pills and the label says not to take grapefruit juice within two hours. Any idea why and what would happen? Just curious.

Grapefruit interactions
 

Grapefruit has certain enzymes which block the liver from metabolizing certain drugs for a period of time. I am not a doctor, but I would think that if they are warning you about this, then it could range from excessively long erection, to something much more serious like liver damage.

I'd follow that direction closely...

Grapefruit juice is a CYP3A4 insoform inhibitor and would likely increase tadalafil (Cialis) exposure if ingested within 2 hours of taking Cialis. The "within 2 hours" precaution also means you should not take Cialis less than 2 hours after ingesting grapefruit juice.

Most people don't have a pharmacology knowledge background where they understand what a CYP3A4 insoform inhibitor is, such as grapefruit juice. Therefore, your pharmacist will label your Cialis prescription with the precaution to not consume grapefruit juice within 2 hours of taking a single dose of the prescription.

Just follow the directions on your prescription and stay safe. :)