BS2560 Pharmacology and Toxicology - D R Davies

Data Handling Question

The pharmacokinetic characteristics of a new preparation of an antipyretic drug, a non-protein bound weak acid, have been determined. The drug, at a dose of 3g, was taken orally by an 80 kg healthy volunteer. Blood samples were withdrawn at regular time intervals and the plasma concentration of the un-metabolised drug was determined using a HPLC technique. The results are shown in the Table:

Time after administration (hr) / Plasma concentration (mg/ml)
0.5 / 2.0
1.0 / 3.2
1.5 / 5.4
2.0 / 7.5
3.0 / 11.9
4.0 / 13.1
5.0 / 11.5
6.0 / 8.7
7.0 / 6.5
8.0 / 4.9

If the bioavailability of this preparation is 67%,

(a) Determine the biological half-life, elimination rate constant , volume of distribution and plasma clearance of the drug.

(b) What conclusions can be drawn about the body distribution of this drug?

(d) What processes are likely to be involved in the renal excretion of this drug?

(e) Increasing the urinary pH by the administration of sodium bicarbonate doubled the renal clearance. Explain this effect.

(f) If the minimum effective plasma concentration is 3.5 mg/ml, comment on the efficiency of this preparation.

Use the Pharmacokinetics programme on the PCs in Bourne Level 2 to help you with these calculations, together with information given in lecture notes and in texrtbook. Log on to the network select academic applications/Biology/Pharmacokinetics

Answers will be posted on the BS2560 web-site later in the term. This is not assessed but will be helpful to you in understanding pharmacokinetic principles.