Academia
Types of Drug Antagonism
The several types of antagonism can be classified as follows: Chemical Antagonism Chemical antagonism involves a direct chemical interaction between the agonist and antagonist in such a way as to render the agonist pharmacologically inactive. A good example is the use of chelating agents to assist in the biological inactivation ... Read More
Factors Affecting Rate of Gastrointestinal Absorption
In addition to the lipid–water partition coefficient of drugs, local blood flow, and intestinal surface area, other factors may affect absorption from the gastrointestinal tract. Gastric Emptying Time The rate of gastric emptying markedly influences the rate at which drugs are absorbed, whether they are acids, bases, or neutral substances. ... Read More
Absorption of Drugs from Alimentary Tract
Oral Cavity and Sublingual Absorption In contrast to absorption from the stomach and intestine, drugs absorbed from the oral cavity enter the general circulation directly. Although the surface area of the oral cavity is small, absorption can be rapid if the drug has a high lipid–water partition coefficient and therefore ... Read More
Types of Drug Receptor Binding
Biological receptors are capable of combining with drugs in a number of ways, and the forces that attract the drug to its receptor must be sufficiently strong and long-lasting to permit the initiation of the sequence of events that ends with the biological response. Those forces are chemical bonds, and ... Read More
Antigens and Immunoglobulins
An antigen is any foreign substance, of whatever origin, that is capable of initiating the production of a specific blood protein called an immunoglobulin (e.g., Ig) that will act against it. The Igs so formed will react specifically with that particular antigen, neutralizing its biological effect. Thus antigens are sometimes ... Read More
Effects of pKa on the Biological Properties of Ionizable Drugs
Acidic drugs (e.g. aspirin) are generally more highly bound to plasma albumin, giving a lower volume of distribution, i.e. they tend to stay in the plasma rather than distribute to the tissues. Basic drugs (including many CNS-acting agents such as phenothiazines) are theoretically more prone to binding to acid glycoprotein, ... Read More
Gluconeogenesis | Formation of Carbohydrates
Gluconeogenesis is a metabolic pathway of glucose formation from amino acids and the glycerol portion of fat. About 60 percent of the amino acids in the body proteins can be converted easily into carbohydrates; the remaining 40 percent have chemical configurations that make this difficult or impossible. Each amino acid ... Read More
Physiology of the Gastrointestinal Tract
The gastrointestinal tract stretches from the mouth to the anus and consists of our main anatomical areas; the esophagus, the stomach, the small intestine and the large intestine or colon. The wall of the gastrointestinal tract is essentially similar in structure along its length, consisting of our principal histological layers: ... Read More
Physiological Factors Influencing Oral Drug Absorption
The gastrointestinal tract is complex. Figure 1 outlines some of the main structures involved in and key physiological parameters that affect oral drug absorption. In order to gain an insight into the numerous actors that can potentially influence the rate and extent of drug absorption into the systemic circulation, a ... Read More
Synaptic Transmitters | Rapidly Acting and Slowly Acting
There are more than 50 chemical substances have been proved or postulated to function as synaptic transmitters. Many of them are listed in below, which give two groups of synaptic transmitters. One group comprises small-molecule, rapidly acting transmitters. The other is made up of a large number of neuropeptides of ... Read More