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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

CHAPTER SUMMARY

 A loading dose (DL) given as an IV bolus injection may be used at the start of an

infusion to quickly achieve the desired steady-state plasma drug concentration.

 For some drugs, IV bolus injections can result in immediate high plasma drug

concentrations and drug toxicity. An IV drug infusion slowly inputs the drug into the

circulation and can provide stable drug concentrations in the plasma for extended time

periods.

 Constant IV drug infusions are considered to have zero-order drug absorption

because of direct input. Once the drug is infused, the drug is eliminated by first-order

elimination.

 A true steady state is achieved when the rate of drug infusion (i.e., rate of drug

absorption) equals the rate of drug elimination.

 Four to five elimination half-lives are needed to achieve 95% of steady state.

 Pharmacokinetic parameters may be calculated from samples taken during the

IV infusion and after the infusion is stopped, which are then used to optimize the

dosing regimen for a patient.

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