WARNING: The reason doing this is contraindicated is because dosages for potentially harmful drugs (Viagra) are based on average absorption with ACTIVE CYP3A4 in normal populations. Inhibiting your CYP3A4 can easily cause overdose of certain medications with potentially dangerous consequences.
If you drink grapefruit juice before your dose, YOU ARE TAKING MORE OF THE DRUG THAN YOU THINK.
READ THE WARNING
Grapefruit juice and the flesh and rind of the grapefruit contain Bergamottin, a moderate inhibitor of the enzyme CYP3A4 in the small intestine. CYP3A4 is present in large quantities in the liver and is responsible for the metabolism of MANY compounds. In the small intestine, it eliminates these compounds before they can be absorbed. Inhibition of CYP3A4 in the intestine results in increased rate and total absorption of its substrates, which include these drugs of interest to you guys:
- Tamoxifen (Nolvadex)
- Anastrozol (Arimidex)
- Toremifene
- Oral Testosterone (Dianabol, Anadrol, etc)
Also potentially of interest:
- Sildenafil (Viagra)
- Diazepam/Alprazolam (Valium/Xanax)
- Codeine
- Most SSRIs and beta blockers
- Most tricyclic antidepressants
- Some antibiotics
- Caffeine
So basically, drinking 250ml (the smallest quantity I've seen in the literature) of pure grapefruit juice (not juice cocktail) 5-15 minutes before taking one of these drugs can increase both the amount absorbed and the rate of absorption.
If you want to experiment with this and you're a regular coffee drinker, drink 250-500ml of grapefruit juice before your normal amount of coffee in the morning. You'll easily notice that the caffeine affects you much more than it should.
Important: Don't think this means you can be cheap and take less dbol for the same effect (at least one person always asks this question). Nobody can tell you exactly how much of an effect you're going to get, so there's no way to confidently say what an equivalent dose would be. All this means is that, if you're already taking a dose you're very comfortable with, you can get a little more effect out of it by taking it with grapefruit juice.
If you're taking a dose that's already as much as you should take, then adding grapefruit juice may give you undesirable side effects or make the side effects worse.