Pharmacodynamics 1 PDF

# Overview of Pharmacodynamics Pharmacodynamics (sometimes described as what a drug does to the body) is the study of the biochemical, physiologic, and molecular effects of drugs on the body and involves receptor binding. - **Receptor sensitivity:** The drug's effect depends on the drug's concentr...

# Overview of Pharmacodynamics Pharmacodynamics (sometimes described as what a drug does to the body) is the study of the biochemical, physiologic, and molecular effects of drugs on the body and involves receptor binding. - **Receptor sensitivity:** The drug's effect depends on the drug's concentration at its target. - **Post-receptor effects:** The drug's effect can be influenced by chemical interactions. - **Chemical interactions:** The drug's effect can also be affected by the relationship between the dose of the drug and its effect. ## Factors that affect pharmacodynamics - **Aging process:** As we age, the way our bodies respond to drugs can change. - **Disease:** Different diseases can cause changes in the levels of signaling proteins, resulting in altered receptor sensitivity. - **Drug-drug interactions:** Because drugs can interact with each other, they can impact the way our bodies respond to drugs. ## Drug Receptor Interactions Receptors are macromolecules involved in chemical signaling between and within the cells. They may be located on the cell's surface membrane or in the cytoplasm. - **Directly:** Some drugs bind directly to receptors, directly regulating cellular processes, such as ion conductance, protein phosphorylation, enzymatic activity. - **Indirectly:** Some drugs bind to receptors called ligands, which indirectly increase or decrease the receptor's activation or inactivation. - **Specificity:** The binding of a drug to a receptor is very specific. - **Selectivity:** Some drugs bind to multiple receptor subtypes, further increasing complexity. ## Chemical Interactions Some drugs produce effects without actually altering cellular function and without binding to a receptor. - **Antacids:** Antacids decrease gastric acidity through a simple chemical reaction. Antacids interact with acids to neutralize and extract salts. - **Cholestyramine:** Cholestyramine is a primary bile acid sequestrant that binds and binds and removes bile acids in the GIT. ## Dose-Response Relationship How a drug's effect is affected by the concentration of drug at the site of action. - **Dose-response curve:** A dose-response curve graphs the relationship between the dose of the drug and the measured effect. - **Interpretation:** - **Efficacy:** The maximum effect a drug can produce. - **Potency:** The amount of drug needed to produce a given effect. - **Slope:** The rate of change in response per unit dose. ## Effect of Aging on Drug Response | Class | Drug | Action | Effects of Aging | |-------------|------------------|---------------------------|----------------------| | Analgesics | Morphine | Acute analgesic, pain relief | ↑ | | | Pentagocone | Analgesic effect | ↑ | | Anticoagulants| Heparin | PTT (chataned) | ↑ (prolonged) | | | Warfarin | PT (prolonged) | ↓ | | Bronchodilator| Albuterol | Bronchodilation | ↑ | | | Ipratropium | Bronchodilation | ↓ | | Cardiovascular drugs | Angiotensin | Decreased | ↑ | | | Receptor Blockers | Increased | ↑ | | | Digoxin | ↑ (decreased clearance) | ↑ | | | Enalapril | ↑ (decreased clearance) | ↑ | | | Felodipine | Acute Hypotension | ↓ | | | Nitroglycerin | Venodilation | ↓ | | | Nifedipine | Arterial vasodilation | ↓ | | | Phenylephrine | Acute Vasoconstriction | ↓ | ## Types of Receptors - **G-protein coupled receptors:** Associated with GTP binding. - **Protein kinases:** Act as a catalyst. - **Transcription factors:** Act as a regulator of DNA transcription.