Pharmacology & Therapeutics Intro 1 PDF

INTRODUCTION TO PHARMACOLOGY Dr Joshua Norman Clinical Pharmacokinetics and Pharmacodynamics Clinical Pharmacokinetics The movement of drugs within the human body or biological systems. ADME : absorption, distribution, metabolism, and elimination of medications Absorption Mus...

INTRODUCTION TO PHARMACOLOGY Dr Joshua Norman Clinical Pharmacokinetics and Pharmacodynamics Clinical Pharmacokinetics The movement of drugs within the human body or biological systems. ADME : absorption, distribution, metabolism, and elimination of medications Absorption Must be able to get medications into the patient’s body DRUG CHARACTERISTICS THAT AFFECT ABSORPTION: – Molecular weight, solubility, & formulation FACTORS AFFECTING DRUG ABSORPTION RELATED TO PATIENTS: – Route of administration, gastric or stomach pH, contents of GI tract Distribution Factors that affect distribution: Membrane permeability – drugs have to cross membranes to site of action Plasma protein (Albumin) binding – bound drugs do not cross membranes – malnutrition = implies low plasma protein (albumin) = higher free drug that leads to higher side effects Metabolism Drugs and toxins are seen as foreign to patients bodies Hence the body works to convert or break down drugs to less active forms and increase water solubility to enhance elimination Drugs can undergo metabolism in the lungs and liver (mainly in the liver). Metabolism Liver - primary route of drug metabolism Liver may be used to convert pro-drugs (inactive) to an active state Elimination Pulmonary = expired in the air Bile from the liver = excreted in faeces Renal (kidneys) Special Patient Populations to noted Under Pharmacokinetics Renal Disease or Kidney disease Hepatic Disease or Liver disease Pharmacodynamics Study of the processes underlying drug action – Mechanism of drug action Drug-receptor interaction – Efficacy – Safety or side effects profile Pharmacodynamics “What the drug does to the body” – Cellular level – General Pharmacodynamics Drug effects THERAPEUTIC EFFECT The desired intended effect produced from the administration of a drug – Examples: – BP lowering – Pain relief – Blood glucose level control Side effect/ Adverse Drug Reaction Unwanted but often unavoidable, pharmacodynamic effects that occur at therapeutic doses E.g. Side effect of Promethazine (Phenergan) (anti-allergic) sedation. Note about Side effects: Drug discovery Occasionally, “adverse” drug effects may be exploited to develop an entirely new indication for a drug Drug discovery examples Unwanted hair growth during Minoxidil treatment of severely hypertensive patients  development of the drug for hair growth. Sildenafil (Viagra) was initially developed as an antianginal, but its effects to alleviate erectile dysfunction (sexual impotence)  led to a new drug indication in erectile tissue TOXIC EFFECT Result of excessive pharmacological action of the drug due to over dosage or prolonged use. Over dosage may be: Accidental, homicidal, suicidal INTOLERANCE Appearance of characteristic toxic effects of a drug in an individual at therapeutic doses Indicates a low threshold of the individual Drug Withdrawal reactions Sudden interruption of therapy with certain drugs result in adverse consequences like worsening of the condition for which the drug was being used for. E.g. Corticosteroid worsening of immune status β-blockers  worsening of angina (chest pains)  TERATOGENICITY/ Teratogenic effect Capacity of a drug to cause foetal abnormalities when administered to the pregnant mother. Drugs can affect the foetus at 3 stages: 1. Fertilization and implantation (Conception to 17 days): failure of pregnancy which often goes unnoticed. 2. Organogenesis(first trimester): most vulnerable period, deformities are produced. 3. Growth and development (second trimester): developmental and functional abnormalities can occur.  Teratogenicity Examples E.g: Thalidomide Phocomelia (malformation of human arms & legs) Anticancer drugs  Cleft palate , hydrocephalus (large head)  Mutagenecity or Mutagenic effects Capacity of a drug to cause genetic defects  CARCINOGENICITY/ Carcinogenic effect Carcinogen is any agent that promotes the development of cancer