Introduction to Pharmacology

Introduction to Pharmacology

• Pharmacology is the study of drugs and their interactions with living organisms.
• It encompasses drug action, drug effects, and the use of drugs to treat diseases.
• Pharmacology involves understanding how drugs are absorbed, distributed, metabolized, and excreted (ADME).
• Drug action is the specific molecular mechanism by which a drug produces its effects.
• Drug effects are the observable changes in the body caused by a drug.

Drug Targets and Mechanisms

• Many drugs exert their effects by interacting with specific molecular targets within the body.
• These targets include proteins like enzymes, receptors, ion channels, and transporters.
• Drugs can act as agonists (mimicking the action of natural molecules), antagonists (blocking the action of natural molecules), or modulators (altering the function of the target).
• Interactions between drugs and targets can be influenced by factors such as drug concentration, affinity, and the presence of other molecules.
• Drug design involves identifying or synthesizing a drug candidate that adheres to specific chemical properties, bioavailability, pharmacokinetics, and efficacy guidelines.

Pharmacokinetics

• Pharmacokinetics describes the movement of drugs within the body.
• Key processes include:
  • Absorption: The process by which a drug enters the bloodstream from its site of administration. Factors influencing absorption include route of administration, drug formulation, and physiological factors.
  • Distribution: Once absorbed, drugs distribute throughout the body via the blood. This involves crossing biological membranes, binding to proteins, and compartmentalization.
  • Metabolism: The process by which a drug is chemically altered in the body, often by enzymes like cytochrome P450s in the liver. Metabolites can be more or less active than the original drug. First-pass metabolism significantly impacts the bioavailability of orally administered drugs.
  • Excretion: The process of eliminating the drug or its metabolites from the body. This primarily occurs through the kidneys, but also via the liver, lungs, and other routes.

Pharmacodynamics

• Pharmacodynamics describes the effects of drugs on the body.
• It focuses on the relationship between drug concentration and response.
• Factors that impact drug response include:
  • Receptor binding affinities
  • Drug potency and efficacy
  • Patient-specific factors like age, gender, genetics, and pre-existing conditions
  • Drug interactions: Simultaneous use of multiple drugs may affect the efficacy or safety of either drug, increasing the risk of adverse events.

Drug Administration and Routes

• Drugs are administered in various ways to target specific needs or achieve specific outcomes.
• Common routes include:
  • Oral (most common, convenient): Absorption occurs in the gastrointestinal tract.
  • Intravenous (IV): Direct administration into a vein allows for rapid drug delivery and precise control of dose.
  • Intramuscular (IM): Injection into muscle tissue; suitable for certain drugs that might cause irritation if injected into a vein.
  • Subcutaneous (SC): Injection under the skin.
  • Topical: Application to the skin or mucous membranes.
• Drug administration considerations involve factors like drug stability, patient comfort, and potential for side effects.

Drug Toxicity and Safety

• Drug toxicity describes adverse effects that arise from drug use.
• Adverse drug reactions (ADRs) encompass a broad range of undesirable effects.
• Drug safety involves evaluating potential risks and benefits of treatment.
• Preclinical studies(e.g., animal models) and clinical trials (e.g., human testing) are crucial for assessing drug safety prior to human use.
• Monitoring patients during and after drug use is fundamental to detect and manage potential toxicities appropriately.
• Drug dosage schedules, and patient monitoring, are vital components of safe medication use.

Therapeutic Drug Monitoring (TDM)

• In cases where drug levels need precise control (e.g., certain chemotherapy drugs, immunosuppressants), TDM is used.
• TDM involves regularly measuring drug concentrations in the patient's blood to ensure the desired therapeutic effect is maintained while minimizing toxicities.
• This helps in determining optimal drug dosages and adjusting them as needed.

Clinical Pharmacology

• Focuses on the practical application of pharmacology in clinical medicine.
• Important areas include:
  • Selecting the most appropriate drug for a particular condition.
  • Determining the correct dosage and frequency.
  • Monitoring for adverse effects.
  • Consideration of drug interactions, individual variability, and other factors that may influence therapy.

Drug Interactions

• Drugs can interact, affecting the action or toxicity of either drug.
• Interactions can be pharmacodynamic, pharmacokinetic, or both.
• Drug interactions can increase or decrease drug efficacy or lead to unexpected or undesirable effects