Pharmacodynamics and Drug Action Quiz

Pharmacodynamics and Drug Action

• Pharmacodynamics examines how drugs influence cell physiology and the body's response to drugs.

Receptors

• Receptors are proteins or nucleic acids influencing physiological and metabolic activities.
• Agonists/Activators: Bind to receptors and produce pharmacologic effects.
• Antagonists/Blockers: Prevent cellular effects by blocking receptor activity.

Pharmacotherapeutic/Indication

• Understand the intended drug effects, including toxic side effects.
• Example: Minoxidil is used to prevent hair loss.

Pharmacokinetics

• Focuses on how the body affects drugs, including absorption, distribution, metabolism, and excretion.
• Onset: Time to reach minimum effective concentration.
• Peak: Time when the drug has maximum effect.
• Duration: Length of time the drug remains effective.

Absorption

• Refers to how drugs enter the bloodstream.
• Bioavailability: Degree and rate at which a drug is absorbed and reaches target tissue.

Factors Affecting Absorption Rate

• Dosage Forms: Includes liquids, suspensions, capsules, tablets, coated, and enteric-coated tablets.
• Route of Administration: Sublingual administration is faster; lipid solubility facilitates absorption.
• GI Motility: Food can delay gastric emptying, impacting drug absorption. Drugs should generally be taken before or between meals.

Specific Drug Administration Guidelines

• Some drugs should be taken on an empty stomach with lots of water, such as:
  • Acetaminophen, cephalosporins, isoniazid, rifampicin.
• Other medications may be taken with food to minimize gastrointestinal irritation.

Plasma-Protein Binding

• Drugs may bind to plasma proteins, impacting their efficacy and metabolism.

Key Terms

• Cumulative Effect: Increased response from repeated doses.
• Drug Tolerance: Diminished response to a drug over time.
• Drug Resistance: Failure of a drug to have the intended effect.
• Drug Dependence: Client's need for a drug.

Excretion

• The primary route of drug elimination is via the kidneys.
• Probenecid is used with penicillin to reduce excretion, while antacids can increase aspirin elimination.

Half-Life

• Indicates how long a drug remains in the system; usually, a drug is considered eliminated after about five half-lives.

Steady-State Accumulation

• Achieved when drug intake equals elimination, leading to consistent therapeutic levels.

Drug Clearance

• Creatinine Clearance is the best renal function indicator; normal values range from 0.6 to 1.2 mg/dL.

Contraindications

• Absolute Contraindications: Drugs that should never be administered.
• Relative Contraindications: Drugs to avoid in specific circumstances (e.g., pregnancy).

Caution with Drug Administration

• Certain drugs require caution, such as magnesium sulfate in pregnant women.

Drug Interactions

• Additive Effect: Combined effect of drugs; e.g., hydrochlorothiazide and BP reduction.
• Potentiation/Synergy: One drug enhancing the effect of another, e.g., Vistaril and Demerol.
• Antagonism: One drug reducing the effect of another, e.g., insulin and steroids.

Side Effects and Toxicity

• Side Effects: Expected but not always harmful (e.g., nausea).
• Toxicity: Potentially harmful effects, such as nephrotoxicity and hepatotoxicity.

Hypersensitivity Reactions

• Occur when patients are sensitive to drug effects, while allergic reactions involve immune responses (e.g., rash, anaphylaxis).

This quiz explores the essential concepts of pharmacodynamics, focusing on how drugs influence cellular physiology. It covers receptor types, their roles as agonists and antagonists, and the pharmacotherapeutic implications, including intended effects and side effects of medications.