Bioequivalence and Bioavailability Forum

I am a pharmacy student currently doing an internship and would like to ask a question regarding WinNonLin (currently nobody here has experience with winnonlin, so I'm kind of learning it myself).

I want to do noncompartmental PK analysis of a drug (drug "A").
The goal is to see whether or not a second drug (drug "B") shows effect on PK parameters of drug A.
The studydrug was administered twice as an IV bolus dose of 1 mg injected over 1-2 minutes, at t=0 min and t=40 min. The half life was estimated at 200 min. On two separate occasions subjects took either only drug A or a combination of drug A and B

The question: What kind of modelsettings/dosing regimen is best to choose?

The drug is dosed twice, but no steady state concentration is reached.
- Should I use an NCA IV bolus model with single dosing (e.g. 2 mg total dose) with time of dosing at t=0.
- Should I use the steady state option in the dosing regimen window, using something as: Dose: 1, Tau=40 min, Last dose=0. In this way I can define the multiple dosing, however, no steady state is reached, so I feel the first option is better.
- Or something else?

Thanks in advance for any tips!