Drug Mechanisms and Pharmacokinetics

Drug Mechanisms

• Drugs produce effects at molecular, cellular, and systemic levels.
• Drugs interact with targets like receptors, enzymes, ion channels, or transporters.
• Receptor binding triggers intracellular events, leading to a physiological response.
• Agonists activate receptors, while antagonists block receptor activation.
• Enzyme inhibitors decrease the activity of specific enzymes, altering biochemical pathways.
• Some drugs act by directly interacting with DNA or interfering with cell structure.

Pharmacokinetics

• Pharmacokinetics describes the movement of drugs within the body via absorption, distribution, metabolism, and excretion (ADME).
• Absorption allows a drug to enter the bloodstream from its administration site, influenced by the route, drug formulation, and physiological factors.
• Distribution is the movement of a drug from the bloodstream to tissues and organs, affected by blood flow, tissue permeability, and plasma protein binding.
• The liver is the primary site of drug metabolism, involving enzymes like cytochrome P450 (CYP) enzymes, which can form active or inactive metabolites.
• Kidneys are the primary organs for drug excretion via urine, with other routes including bile, feces, sweat, and exhaled air.
• Understanding ADME is crucial for determining appropriate drug dosages and dosing intervals.

Adverse Effects

• Adverse effects are unintended and undesirable effects of drugs, ranging from mild to severe and including side effects, allergic reactions, and toxicities.
• Side effects are predictable and often related to the drug's primary mechanism of action.
• Allergic reactions are immune-mediated responses to drugs, and can be life-threatening.
• Toxicities result from excessive drug exposure, and lead to organ damage or dysfunction.
• Risk factors for adverse drug reactions include age, sex, genetics, and pre-existing medical conditions.
• Monitoring for adverse effects is a critical aspect of drug therapy.

Pharmacodynamics

• Pharmacodynamics describes the effects of drugs on the body and their mechanisms of action and involves understanding the relationship between drug concentration and drug effect.
• Key concepts are dose-response relationship, potency, efficacy, and therapeutic index
• The dose-response relationship describes the relationship between the dose of a drug and the magnitude of its effect.
• Potency refers to the amount of drug needed to produce a given effect.
• Efficacy refers to the maximum effect a drug can produce.
• The therapeutic index is a measure of drug safety, comparing the dose required for a therapeutic effect to the dose that causes toxicity.
• Understanding pharmacodynamics is essential for optimizing drug therapy and minimizing adverse effects.

Therapeutic Uses

• Therapeutic uses refer to the clinical applications of drugs in the treatment, prevention, or diagnosis of diseases.
• Drugs are used to alleviate symptoms, modify disease processes, or prevent disease occurrence.
• The selection of a drug for a particular condition depends on efficacy, safety, and patient-specific factors.
• Drug therapy should be individualized based on the patient's needs and characteristics.
• Monitoring the effectiveness of drug therapy is essential to ensure optimal outcomes.