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Related Concept Videos

Combined Effects of Drugs: Antagonism01:30

Combined Effects of Drugs: Antagonism

The combined effects of drugs can result in various interactions, of which an important type is antagonism. Antagonism is a mechanism where one drug inhibits or counteracts the effects of another drug. Antagonism can occur through various means, including receptor binding, allosteric modulation, functional interaction, chemical reactions, and pharmacokinetic processes.
The most common type is receptor antagonism, where one drug acts as an antagonist to block the effects of another drug by...
Combined Effects of Drugs: Synergism01:27

Combined Effects of Drugs: Synergism

Synergism is a useful mechanism where combining two or more drugs is more effective than each constituent used alone. Such combinations are also called supra-additive interactions. The drugs collectively enhance the final therapeutic effect by acting on different targets. Another advantage is that the low dose of each constituent drug is sufficient to achieve the desired effect. This helps reduce the duration of therapy and lower the adverse effects of these drugs.
Such synergistic combinations...
Pharmacokinetics: Drug–Drug Interactions01:25

Pharmacokinetics: Drug–Drug Interactions

Drug interactions occur when the pharmacological effect of one drug is altered by another substance, either enhancing or diminishing its activity. The drug whose activity is altered is known as the object drug, and the substance causing the alteration is called the agent drug or the precipitant. The net effects of these interactions are mostly undesirable, leading to decreased effectiveness or increased adverse effects. In rare cases, interactions can be beneficial, such as the enhanced...
Agonism and Antagonism: Quantification01:14

Agonism and Antagonism: Quantification

When drugs are administered, they can elicit either an agonist or antagonist effect on the body. Agonism occurs when a drug activates a specific receptor, triggering a biological response. On the other hand, antagonism happens when a drug binds to the same receptors but blocks their activation, thereby preventing a biological response.
To quantify these effects, researchers use a dose-response curve, which provides valuable information about the potency and efficacy of a drug. Potency refers to...
Drug toxicity: Drug–Drug Interaction01:30

Drug toxicity: Drug–Drug Interaction

Drug–drug interactions can precipitate toxicity through multiple mechanisms. Absorption interactions alter how drugs enter the body, exemplified when ranitidine increases the absorption of basic drugs, while cholestyramine decreases the levels of propranolol. Protein binding interactions occur when drugs share the same binding sites on plasma proteins. Drugs like aspirin and warfarin, when bound in excess, can lead to increased free drug concentrations, enhancing the potential for...
Nonlinear Pharmacokinetics: Dependence of Elimination Half-Life and Dose Clearance01:23

Nonlinear Pharmacokinetics: Dependence of Elimination Half-Life and Dose Clearance

The elimination half-life and drug clearance of drugs following nonlinear kinetics can vary with dosage. The Michaelis-Menten parameters and drug concentration influence these factors. As the dose increases, the elimination half-life tends to lengthen, resulting in a reduction in clearance and a disproportionately larger area under the curve. The total clearance can be derived from the Michaelis-Menten equation for drugs following a one-compartment model.
A study on guinea pigs examined the...

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Diagonal Method to Measure Synergy Among Any Number of Drugs
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Published on: June 21, 2018

Paradoxical and bidirectional drug effects.

Silas W Smith1, Manfred Hauben, Jeffrey K Aronson

  • 1Department of Emergency Medicine, New York University School of Medicine, New York, NY 10016, USA. Silas.Smith@nyumc.org

Drug Safety
|January 26, 2012
PubMed
Summary
This summary is machine-generated.

Paradoxical drug reactions produce unexpected outcomes, complicating patient care and pharmacovigilance. Understanding these diverse effects across drug classes is crucial for clinical management and toxicology.

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Area of Science:

  • Pharmacology
  • Clinical Toxicology
  • Drug Reaction Mechanisms

Background:

  • Paradoxical drug reactions yield outcomes opposite to expected drug actions.
  • Bidirectional drug reactions can produce opposing effects in individuals.
  • These reactions occur across diverse drug classes and can be beneficial or adverse.

Purpose of the Study:

  • To review paradoxical and bidirectional drug effects and their mechanisms.
  • To provide a compendium of reactions across various drug classes.
  • To discuss clinical toxicological considerations of these effects.

Main Methods:

  • Literature review of paradoxical and bidirectional drug effects.
  • Analysis of mechanisms at various biological system levels.
  • Compilation of examples from multiple drug classes.

Main Results:

  • Paradoxical effects are often adverse, complicating adverse drug reaction assessment.
  • Bidirectional effects can be clinically useful or adverse.
  • Mechanisms involve receptor interactions, stereochemistry, and complex biological feedback loops.

Conclusions:

  • Paradoxical and bidirectional drug effects present complex challenges in clinical management.
  • Understanding underlying mechanisms is vital for predicting and managing these reactions.
  • A comprehensive review aids in pharmacovigilance and toxicological assessment.