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.
