PK + PD Together

PK Meets PD: The Time Course of a Drug's Effect

You have followed a drug through absorption, distribution, metabolism and elimination — that is pharmacokinetics (PK): what the body does to the drug. You have watched it bind receptors and produce a response — that is pharmacodynamics (PD): what the drug does to the body. This chapter is where the two finally meet, on the axis they share: TIME. When does the effect start, peak and fade? Does it rise and fall with the blood level — or can a drug be long gone from the blood and still working a week later? Aspirin will show you the strangest answer.