Chapter 3 Biopharmaceutics and Pharmacokinetic Introduction

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Absorption versus Particle Size

redrawn from Prescott et al., 1970

Fig 3.15.1 Slide showing plasma phenacetin versus time curve after oral administration of 1.5 g in various suspension dosage forms. The effect of particle size on drug absorption is shown in this slide. Generally speaking the smaller the particle size the quicker the absorption. By increasing the particle surface area it is possible to increase the dissolution rate. However very small particle can clump together. Therefore a wetting agent such as Tween 80 can have a beneficial effect on the overall absorption. The intestinal fluids usually contain some materials which can act as wetting agents, however drug dissolution testing in vitro may neglect this effect.

References

Prescott, L.F., Steel, R.F. and Ferrier, W.R. 1970 The effects of particle size on the absorption of phenacetin in man, Pharmacol. Therap., 11, 496-504

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