Overview of Pharmacokinetics and Pharmacodynamics

Dose = Amount of drug at absorption site + Amount of drug in the body 

Studies of dmg absorption, distribution and elimination comprise what is referred to as pharmacokinetics. By contrast, the concentration of a pharmaceutical compound at the site(s) of action in relation to the magnitude of its effect(s) is referred to as pharmacodynamics. Both pharmacokinetics and pharmacodynamics have their roots in physiology, chemical kinetics, biochemistry, and pharmacology. They seek to provide a mathematical basis of the absorption, distribution, metabolisms, and 

Clearance is an important concept of pharmacokinetics that describes the rate at which a chemical is eliminated from the body. The total clearance of a dmg from the body is calculated from 

A portion of the pharmaceutical can be excreted via the kidney, that is, renal excretion. Thus, renal excretion (Fg) can range between 0 and 1 with the latter representing a simation in which renal excretion is the only route of elimination. Renal excretion can be estimated from 

By definition, the fraction that enters the circulatory system is eliminated by extrarenal mechanisms (usually metabolism by the liver and other tissues) and is derived by the difference from renal excretion that is, 1 — Fg. The excretory organs are able to eliminate polar compounds such as tetracycline and tylosin more efficiently than compounds that are highly soluble in lipids (i.e., lipophilic) such as metronidazole, erythromycin, clindamycin, and trimethoporin. Thus, the highly lipophilic compounds will not be eliminated until they are metabolized to more polar intermediates. 

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Joshi, A., Bauer, R., Kuebler, P, White, M., Leddy, C., Compton, P., Garovoy, M., Kwon, P., Walicke, P., and Dedrick, R. 2006. An overview of the pharmacokinetics and pharmacodynamics of efalizumab a monoclonal antibody approved for use in psoriasis. Journal of Clinical Pharmacology 46(1), 10-20. 

Nix DE, Majumdar AK, DiNubile MJ. (2004) Pharmacokinetics and pharmacodynamics of ertapenem An overview for clinicians. J Antimicrob Chemother 53 23-28. 

VaishampayanU, Parchment RE, JastiBR, Hussain M. Taxanes an overview of the pharmacokinetics and pharmacodynamics. Urology 1999 54(6A Suppl) 22-29. 

A comparative study of the pharmacokinetic and pharmacodynamic properties of the more modern fluoroquinolones [218,219], as well as overviews on the pharmacokinetics [163,220] and pharmacodynamics [221] of moxifloxacin, can be found in the literature. 

Benzodiazepines do not induce their own metabolism, and thete is no evidence for the development of pharmacokinetic toletance (Gteenblatt and Shader 1986). The behavioral tolerance seen with chronic dosing is explicable entirely on the basis of pharmacodynamic tolerance (as described earlier in the overview of neuropharmacology). 

Fig. 1. Overview of pharmacology. Pharmacokinetics (PK) relates to the effect of the body on the drug and principally includes bioavailability, distribution, and clearance. Pharmacodynamics (PD) relates to drug concentration and receptor availability. The response to drug concentrations may be therapeutic, subtherapeutic, or toxic, depending on considerations involving both PK and PD principles. From Linder MW, Valdes R Jr. Pharmacogenetics fundamentals and applications. Therapeutic drug monitoring and toxicology. AACC 1999 20(l) 10 with permission.)...

Merck Manual of Diagnosis and Therapy. Sec. 22 Clinical Pharmacology. URL http //www.merck.com/mrkshared/ mmanual/section22/sec22.jsp. [25 October 2005]. Free Web version of the Merck Manual. Clinical Pharmacology section provides an overview of the basic concepts of pharmacokinetics, pharmacodynamics, and toxicity. 

The purpose of this chapter is to provide an overview of the pharmacodynamic and pharmacokinetic properties of chiral drugs in... 

In spite of the move towards single stereoisomer products, the number of agents currently available as racemates is considerable, and for the majority of these relatively little is known with respect to the pharmacodynamic, pharmacokinetic, or toxicological properties of the individual enantiomers present in such mixtures. This chapter is not intended to be an exhaustive compilation of stereoselectivity in drug action but aims to provide an overview, illustrate some of the complexities that may arise, and indicate the significance of stereochemical considerations in pharmacology. More detailed evaluation of individual classes of drugs are presented in Chaps. 6 and 7. 

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