Re: Error message (continued..)

From:Nick Holford Subject:Re: [NMusers] Error message (continued..) Date:Fri, March 8, 2002 3:18 am Emily, Looks like a reasonable model for oral phenytoin. I am guessing this is the primary drug of interest because you have carbamazepine and valproate as covariates and your inital estimate of Vmax=400 mg/d, Km=4 mg/L and V of 80L would be reasonable for phenytoin. However, because the default units for TIME when you use DATE=DROP and TIME with PREDPP are hours the initial estimate of Vmax would be 24 times too big. However, irrespective of my guess for the drug I have difficulty with K12 (or Ka in more usual terminology). You have an initial estimate of 0.0023 ie. an absorption half-life of 301 h. I don't know of any oral formulation that would be described reasonably by such a long half-life. So my suggestion to you is first of all to think hard about the time units you are using here. I very much doubt you can get any reasonable solution with these initial estimate values. Nick Nick Holford, Divn Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x6730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/