Drug Actions and Potency Comparison

Drug Actions

• Efficacy versus potency are important in drug selection.
• Comparing drugs' responses when acting on the same or different receptors is important.
• Understanding potentiation and antagonism is crucial in therapy.
• Predicting drug safety and toxicity through quantal dose-frequency curves is essential.
• Graded dose-response curves are used in therapy.

Quantitative Comparison of Drug Effects (Same Receptor)

• Comparing agonists (B, C, D, E, F) to a full agonist (A) shows potency differences (e.g., E > A).
• Agonists B, C, and E may have the same efficacy as A.
• Drugs D and F have less efficacy than A (D < F).

Effect of Adding Another Drug

• Adding a drug that shifts the dose-response curve to the left increases potency.
• Adding a drug that shifts the curve to the right decreases potency.
• A drug shifting the curve parallel to the right, overcome by increasing agonist concentration, is a competitive reversible antagonist.
• A drug shifting the curve to the right non-parallel and not overcome by increased agonist concentration is a competitive irreversible or non-competitive antagonist.

Quantitative Comparison of Drug Effects (Different Receptors)

• Drugs acting on different receptors can vary in efficacy.
• Drugs acting on different receptors cannot be compared in terms of potency.
• If one drug increases the action of another drug acting on a different receptor, it's called synergy or potentiation.

Quantal Dose-Response Curve

• Used to predict drug safety.
• Median Effective Dose (ED50): drug dose for half the population to have a therapeutic response.
• Median Toxic Dose (TD50): drug dose for half the population to show a specific toxic response.
• Therapeutic Index (TI): TD50/ED50; a high TI indicates drug safety.

Drug Safety and Monitoring

• Drugs with a narrow therapeutic window require monitoring of blood drug concentrations (therapeutic drug monitoring).
• Drugs with wide therapeutic windows don't need monitoring.

Drug Response Variations

• Drug responses can be reduced (tolerance), increased (hypersensitivity), or altered (idiosyncratic reactions).
• Tolerance is often related to repeated drug administration.
• Drug hypersensitivity can be due to genetic defects or immune responses.

Nucleotides & Nucleic Acids

• Nucleic acids are vital biological molecules.
• DNA and RNA comprise nucleic acids.
• Nucleotides are monomers made of three parts:
  • 5-carbon sugar (ribose or deoxyribose).
  • Phosphoric acid.
  • Nitrogenous bases (purines or pyrimidines).
• Pyrimidines include cytosine, thymine, and uracil.
• Purines include adenine and guanine.
• DNA is a double helix with complementary base pairing (A-T, G-C).
• DNA is located in the nucleus and mitochondria.

Functions of DNA

• DNA carries genetic material.
• DNA is responsible for protein synthesis.

Ribonucleic Acid (RNA)

• A type of nucleic acid, with three main types.
• Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes.
• Transfer RNA (tRNA): Carries amino acids to ribosomes.
• Ribosomal RNA (rRNA): Helps synthesize proteins in ribosomes.

Explore the intricacies of drug actions, focusing on the concepts of efficacy and potency in drug selection. Learn to compare different drugs acting on the same receptors and understand the importance of dose-response curves in predicting safety and efficacy. This quiz covers essential pharmacological principles relevant to therapeutic applications.