[donocco]

Ill have to check on the half life of Arimidex etc. The general pharmacy rule is that it takes 5 half lives to get a steady state blood concentration. Once you reach steady state the drug starts to work. The prototype example is the anti-seizure drug Dilantin. Its half life in adults is about 24 hours so you have to take it for about 5 days before you get a steady state concentration that will suppress siezures. Docs circumvent this by giving a loading dose of Dilantin of 1000mg the first day ie three 100mg Dilantin capsules in the morning of the first day, three capsules in the afternoon and 4 capsules at bedtime. This gives you a therapeutic blood level on the first day. All the following days, the patient will take the usual Dilantin dosage of 400mg daily often 4X100mg capsules at bedtime.

If the half life of arimidex is 2 days it should only take anout 10 days to reach an effective steady state level however its possible that the Arimidex is a prodrug that the body changes to an active drug and this active drug has a half life of maybe 5 days so it takes weeks to get a steady state level. Ill check this out.

I remember an incident that happened when I worked the night shift at a Longs drug store in Santa Monica California. It was one of those difficult days. One patient was on the diet pill Fastin and the doctor never called back about the refill request. He asked me for 3 Fastins to cover him over the weekend. I can only do this with blood pressure meds, seizure meds, anti rejection meds etc. The pharmacy law does not allow me to do this with Fastin which is a controlled amphetamine like drug. He had a temper tantrum and called me every name in the book and called for the manager who tried to push me to give him a few pills. I refused citing the law. More tantrum more insults etc.

Finally he left. About 10 minutes later the technician told me there was a woman who wanted to speak to the pharmacist. She was crying and I said to myself "My God what now?" I spoke to her. She was a breast cancer patient on Tamoxifen 10mg twice a day and missed a day. She was sure the breast cancer was going to come back because of her carelessness.

I brought her a package insert on Tamoxifen and showed her that the half life of Nor-Tamoxifen the active drug (Tamoxifen itself is an inactive prodrug) is 21 days. Missing one days dose would have no effect. I told her I hoped and prayed that the cancer would not return but it could return (she knew this) and if it did there was absolutely no way she could assume blame saying "I missed one 10mg dose of Tamoxifen." I took a 100 pound weight off of her back. Being a pharmacist dealing with the public has a few "moments of usefulness."

I'm sure many of you are aware that drugs that inhibit the enzyme Cyp2D6 shouldn't be taken with Tamoxifen. Examples of such drugs are Fluoxetine (Prozac) and Bupropion
(Wellbutrin) both antidepressants. The reason is the body uses theis Cyp2D6 enzyme to change the inactive Tamoxifen to the active Nor-Tamoxifen. There are other drugs that inhibit Cyp2D6 such as Dextromethorphan and Quinidine. Sorry this has been so long.

Paul