# PharmPK Discussion - Prediction of Steady-state parameters from single dose

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• On 15 Sep 2003 at 10:24:29, Hanna-Liza Jooste (hanna-liza.jooste.-at-.qdotpharma.com) sent the message
`Dear all,I need to predict steady-state parameters from single dose results(this is new to me).Can anyone guide me with information on how to do this?...i.e. basicprinciples to use?ThanksHanna-LizaBiostatisticianQdotPharmaSouth Africa`
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• On 16 Sep 2003 at 09:30:41, Toufigh Gordi (tgordi.-a-.buffalo.edu) sent the message
`The following message was posted to: PharmPKDear Hanna-Liz,Generally, it should be quite simple. You may obtain estimates of CLand Vd from your single dose study and use them to predict Cssaccording to:1) Css= Dose*F / (CL*tau) or2) Css=R0/CL or3) Css=AUC (single dose)/tauwhere F is bioavailability, tau is dosing frequency, and R0 is infusionrate. The volume term will help you to estimate the maximum and minimumconcentrations at steady state according to:4) Css,max= D*F / (Vd*(1-exp(-k x tau))5) Css,min= Css,max*exp (-k x tau)where k is equal to CL/Vd. Knowing the half-life of the compound willhelp you to have an estimation of how long it will take to reach theCss, i.e. roughly after 4 half-lives.There are a couple of issues one should be aware of. If your aim withrepeated dosing is to maintain a certain concentration (Css),accumulation takes place, meaning that your Css will be higher than theconcentrations observed after the initial single dose. One must makesure that the kinetics of the compound is the same, i.e. CL or Vd arenot changed with concentration. Thus, your single dose study shouldhave covered several different doses.The second issue is the variability, including inter-occasionalvariability. This could become a major issue, specially if oral dosesare given. Different variability terms can be estimated using data fromthe single dose study.Toufigh Gordi`
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• On 19 Sep 2003 at 10:29:17, "David S. Farrier" (DFarrier.-at-.SummitPK.com) sent the message
`The following message was posted to: PharmPKHanna-LizaThere is a handy list of pharmacokinetic equations available on our website at www.SummitPK.com that includes calculations of multiple doseparameters from single dose data.While there, take a look at our pharmacokinetics data analysis softwarePK Solutions, which makes pharmacokinetic analysis easy, and includesextrapolation of single dose data to multiple dose results.DavidDavid S. FarrierSummit Research Serviceswww.SummitPK.com`
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