Potency and efficacy

 Potency and efficacy

Two concepts that at this stage should not present us with any difficulty are the `potency' and `efficacy' of a drug. The potency is a function of the amount of drug required for its specific effect to occur; it is measured simply as the inverse of the EC50 for that drug. In contrast, the efficacy measures the maximum strength of the effect itself, at saturating drug concentrations. Thus, in Figure 3.10, drug Red exceeds drug Black in potency, while the opposite is true of the efficacy.

Comments

Post a Comment

Popular posts from this blog

Magnitude of Maternal Health problem in Ethiopia

  Magnitude of Maternal Health problem in Ethiopia   Maternal mortality is one of the health indicator which shows the burden of disease and death; the greatest differential between developing and developed countries. More than 150 million women become pregnant in developing countries each year and an estimated 500, 000 of them die from pregnancy related causes. Other than their health problems most women in the developing countries lack access to modern health care services and increase the magnitude of death from preventable problems. Lack of access to modern health care services has great impact on increasing maternal death. Most pregnant women do not receive antenatal care; deliver with out the assistance of trained health workers etc. The life time risk of death as a result of pregnancy or child birth is estimated at one in twenty – three for women in Africa, compared to about one in 10,000 for women in Northern Europe 75% of Maternal morbidity and mortality related to pregnancy a
Read more

Drug application and uptake - Pharmacokinetics

Image
  Drug application and uptake   You are certainly aware that drugs are applied by various routes; the choice depends largely on the pharmacokinetic properties of the drug in question. Table 2.1 lists some characteristics of the major routes.   We will look at the various routes of application in turn. Oral uptake is the most common one, so let's start with this one.   Oral drug application   Inside the digestive tract, drug molecules encounter a quite aggressive chemical milieu. E.g., the acidic pH in the stom-ach (pH ~2) and the presence of proteases and nucleases in the gut preclude the application of proteins, nucleic acids, and other labile molecules. The gut mucous membrane presents a barrier to uptake; many drugs are not able to ef-ficiently cross it by way of diffusion.   For those drugs that make it from the gut lumen into the blood, the liver presents another formidable barrier. All blood drained from the intestines (as well as the spleen and the pancreas) is first passed
Read more

Pharmacokinetics

  Pharmacokinetics   Whatever the actual mechanism of action of a drug may be, we will want to know: Does the drug actually reach its site of action, and for how long does it stay there? This is governed by three factors:   1.    Absorption: Uptake of the drug from the compartment of application into the blood   2.    Distribution: Transport / equilibration between the blood and the rest of the organism   3.    Elimination: Filtration and secretion in the kidneys; chemical modification in the liver   Broadly speaking, absorption and distribution determine the whether a drug will be available at its target site at all, while elimination determines for how long the drug effect will last. The issues of drug absorption, distribution and elimination are collectively referred to as `pharmacoki-netics'.
Read more