Be careful. If you feel that amount of effect that quickly, you are almost certainly taking too much. That single dose after full absorption may be enough to drop you E2 below the desired amount. Subsequent doses may crash your E2 level if you are repeat dosing. Steady state of the drug takes around 7 days. This means your initial result in 15 minutes is a tiny fraction of what ongoing dosing would do. Even your first dose would take the better part of 2 hours to peak. You do not want higher levels of anastrzole in your system than what keeps you E2 in the desired range.
The following is based on 1mg/day on label dosing, but these pharmokenetics also apply to lower amounts.
From:
Arimidex Monograph for Professionals - Drugs.com
Arimidex Pharmacokinetics
Absorption
Bioavailability
Rapidly and well absorbed after oral administration, with peak plasma concentrations usually attained within 2 hours under fasting conditions.
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Steady-state plasma concentrations achieved in about 7 days.
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Onset
Serum estradiol concentrations reduced by approximately 70% within 24 hours of a 1-mg dose
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Duration
Suppression of serum estradiol concentrations maintained for up to 6 days after discontinuance of daily anastrozole administration.
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Food
Food reduces rate but does not affect extent of absorption.
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