Introduction to Pharmacology for Higher Education

Pharmacology lecture that discusses the fundamental definitions and concepts of pharmacology for a psychopharmacological perspective for higher education/university students

1. Pharmacology

2. Pharmacology is the branch of science that studies drugs, their actions, interactions, and effects on the body.

3. Drug : Any chemical substance that produces a biological effect in the body. Pharmacy : The science and practice of preparing and dispensing drugs.

4. Pharmacokinetics The study of how a drug moves through the body, encompassing the processes of absorption, distribution, metabolism, and excretion (ADME).

5. Pharmacokinetics Absorption : How a drug enters the bloodstream. Distribution : How a drug is transported throughout the body. Metabolism : How a drug is chemically altered in the body, primarily in the liver. Excretion : How a drug or its metabolites are eliminated from the body, usually via urine or feces.

6. Pharmacodynamics The study of the biochemical and physiological effects of drugs and their mechanisms of action .

7. Pharmacodynamics Receptor Binding : How a drug interacts with specific cellular targets. Dose-Response Relationship : The relationship between the dose of a drug and the magnitude of its effect. Therapeutic Window : The range of drug doses that elicit a therapeutic response without causing significant adverse effects.

8. Pharmacogenomics The study of how genetic variation affects an individual’s response to drugs.

9. Pharmacotherapeutics The use of drugs to diagnose, treat, and prevent diseases. Indication : The medical condition for which a drug is prescribed. Contraindication : A situation where a drug should not be used because it may be harmful. Side Effects : Unintended effects of a drug that occur in addition to the desired therapeutic effects.

10. Toxicology The study of the adverse effects of chemicals, including drugs, on living organisms. Toxic Dose : The dose of a drug that causes harmful effects. LD50 (Lethal Dose 50%) : The dose at which 50% of a population is expected to die from drug toxicity . Antidote : A substance that can counteract the effects of a poison or overdose.

11. Pharmacovigilance The science and activities related to detecting, assessing, understanding, and preventing adverse effects or any other drug-related problems.

12. Pharmacovigilance Adverse Drug Reactions (ADRs) : Harmful or unintended responses to a drug at normal doses. Post-Marketing Surveillance : Monitoring the safety of a drug after it has been released on the market.

13. Bioavailability The proportion of a drug that enters the circulation when introduced into the body and is able to have an active effect. First-Pass Effect : The metabolism of a drug within the liver after oral administration, reducing the amount of active drug reaching systemic circulation. Intravenous Administration : Provides 100% bioavailability as the drug directly enters the bloodstream.

14. Half-Life (T½) The time it takes for the concentration of a drug in the bloodstream to reduce by half. Steady-State : The point at which the drug's intake and elimination are balanced, leading to a consistent level of drug in the blood. Clearance : The rate at which a drug is removed from the body.

15. Agonist A substance that binds to a receptor and activates it, mimicking the action of a natural neurotransmitter or hormone. Full Agonist : Produces a maximal biological response. Partial Agonist : Produces a submaximal response, even when fully occupying the receptor.

16. Antagonist A substance that binds to a receptor but does not activate it, blocking the action of agonists. Competitive Antagonist : Binds to the same receptor site as the agonist, preventing its action. Non-Competitive Antagonist : Binds to a different site on the receptor, reducing the effect of the agonist.

17. Efficacy The ability of a drug to produce a desired therapeutic effect. Intrinsic Activity : The ability of a drug to activate a receptor and produce a physiological response. Maximum Efficacy : The greatest effect a drug can produce, regardless of dose.

18. Potency The amount of drug needed to produce a given effect. High Potency : Requires a lower dose to achieve the desired effect. Low Potency : Requires a higher dose to achieve the same effect.

19. Therapeutic Index (TI) A ratio that compares the toxic dose to the therapeutic dose of a drug, used to assess the safety of a drug. High TI : Indicates a large margin between therapeutic and toxic doses, generally safer. Low TI : Indicates a narrow margin, requiring careful dosing and monitoring.

20. Synergism When two or more drugs work together to produce a greater effect than either would Additive Effect : The combined effect of two drugs equals the sum of their individual effects. Potentiation : One drug enhances the effect of another.

21. Tolerance The reduction in response to a drug after repeated use, requiring higher doses to achieve the same effect. Pharmacodynamic Tolerance : Due to changes at the receptor level. Metabolic Tolerance : Due to increased drug metabolism.

22. Dependence A physiological or psychological need for a drug, leading to withdrawal symptoms when the drug is not taken. Physical Dependence : Characterized by withdrawal symptoms when drug use is discontinued. Psychological Dependence : Involves emotional or mental preoccupation with the drug.

23. Placebo Effect A beneficial effect due to the patient's belief in the treatment, not attributed to the actual pharmacological action of the drug. Placebo : An inert substance given to a patient, often used in clinical trials. Nocebo Effect : A negative response to a placebo, due to negative expectations.

24. Prodrug An inactive substance that is metabolized in the body to become an active drug. Activation : The conversion of a prodrug into its active form, usually in the liver. Advantages : Often used to improve the bioavailability, solubility, or reduce side effects of the active drug.

25. Idiosyncratic Reaction An abnormal, unpredictable reaction to a drug, not related to the dose or known side effects. Genetic Factors : Often linked to genetic differences in drug metabolism or receptor sensitivity. Unpredictability : Such reactions are not dose-dependent and are rare.

26. Drug Interaction The effect of one drug is altered by the presence of another drug, food, or substance. Pharmacokinetic Interactions : Affects ADME processes. Pharmacodynamic Interactions : Affects the action of the drug at the receptor level. Types : Includes synergistic, antagonistic, and additive interactions.

27. Basic Pharmacological Definitions Pharmacology: Study of drugs and their effects on the body. Drug :Any chemical that affects body functions. Pharmacy: Science of preparing and dispensing medicines. Therapeutics: Use of drugs for treatment of diseases.

28. Basic Pharmacological Definitions Absorption: Entry of a drug into blood from site of administration. Distribution: Movement of drug through blood to body tissues. Metabolism: Breakdown of drug, usually in the liver. Excretion: Removal of drug from the body (urine, feces).

29. Basic Pharmacological Definitions Half-life: (t½) Time for drug concentration in blood to reduce by half. Bioavailability: Fraction of drug dose reaching bloodstream in active form. Mechanism of Action: How a drug works to produce effects.

30. Basic Pharmacological Definitions Agonist: Drug that activates a receptor. Antagonist: Drug that blocks a receptor. Potency: Amount of drug needed for an effect. Efficacy: Maximum effect a drug can produce.

31. Basic Pharmacological Definitions Therapeutic Index :Safety margin: toxic dose ÷ effective dose. Adverse Drug Reaction: Harmful or unwanted drug effect. Side Effect: Secondary, usually unwanted effect of a drug.

32. Basic Pharmacological Definitions Tolerance: Reduced response after repeated drug use. Dependence: Body adapts to drug withdrawal if stopped. Placebo: Inactive substance with no real drug effect. Contraindication: Situation where drug use is unsafe.

33. Pharmacognosy : Study of drugs obtained from natural sources (plants, animals, minerals). Pharmaceutics : Science of formulation, preparation, and proper use of medicines. Pharmacogenetics : Study of how genetic differences affect individual responses to drugs.

34. Loading dose Single dose to achieve the desired plasma level rapidly following by infusion to maintain the steady state. It can be given is single dose or series of doses (mainly done for drugs that are more toxic – digitalis) Loading doses are given if the time required to achieve half life is relatively long and therapeutic benefit drug is required immediately eg : lidocaine for antiarrhythmic patient.

35. Therapeutic Index (TI) A measure of a drug's safety, calculated as the ratio of the toxic dose to the effective dose (TI = TD50/ED50). A high TI indicates a wide margin of safety, while a low TI indicates a higher risk of toxicity.

36. Therapeutic Index (TI) Ratio of the dose that produces toxicity to that produces effective response in the individuals. TI = TD50/ED50 ED50 means median effective dose i.e. . The dose at which 50 % individuals exhibit the specific response . TD50 means toxic dose i.e. the dose that required to produce a particular toxic effect in 50% of individuals.

37. Significance of Therapeutic index High LD 50 gives a wide safety margin in case of inappropriate dosing , while low ED 50 means that only small amount is required for therapeutic effect. Therefore the higher TI the safer is the drug.

38. Drug Development and Regulation Preclinical Studies : In vitro and animal testing. Clinical Trials : Phase I: Safety in healthy volunteers. Phase II: Efficacy in patients. Phase III: Large-scale trials for approval. Phase IV: Post-marketing surveillance. Regulatory Authorities : FDA (USA), EMA (Europe), CDSCO (India).

39. Special Considerations in Pharmacology Pediatrics : Adjusting doses for neonates and children (immature liver metabolism). Geriatrics : Reduced drug clearance, polypharmacy concerns. Pregnancy & Lactation : Teratogenic drugs (thalidomide, isotretinoin ).

40. Half life of drugs. It is time required to eliminate half of the amount of a drug in the body or reduce plasma concentration by 50% Factor altering the half life : age , disease and pregnancy , lactation Physiological variables can alter drug clearance or volume of distribution

41. Half life is increased due to Decreased renal or hepatic plasma flow eg : cardiogenic shock , HF , hemorrhage Decreased extraction ration eg : Renal disease Decreased metabolism Half life is decreased due to Increase hepatic blood flow Decrease protein binding Increase metabolism Increase volume distribution

42. Bioavailability It is the fraction of administered dose of a drug that reaches the systemic circulation in an active form The route by which a drug is administered, as well as the chemical and physical properties of the agent, affects is bioavailability.

43. FACTORS MODIFYING DRUG EFFECTS Age:  Neonates and elderly have altered PK/PD (e.g., reduced liver/kidney function). Body Weight & Size:  Doses often need to be adjusted (e.g., mg/kg). Sex:  Differences in body composition and hormones can affect drug distribution and metabolism.

44. FACTORS MODIFYING DRUG EFFECTS Genetics:  Genetic polymorphisms can make someone a fast or slow metabolizer of a drug. Route of Administration:  Affects the speed and intensity of the response. Disease State:  Liver or kidney disease drastically alters drug elimination.