Introduction to Toxicology PDF

Introduction to Toxicology Rehab S. Abelrahman, PhD Associate Professor of Pharmacology &Toxicology College of Pharmacy, Taibah University  Definitions Toxicology: It is the study of the adverse effects (toxicities) of chemical or physical agents on bio...

Introduction to Toxicology Rehab S. Abelrahman, PhD Associate Professor of Pharmacology &Toxicology College of Pharmacy, Taibah University  Definitions Toxicology: It is the study of the adverse effects (toxicities) of chemical or physical agents on biological systems under specific conditions of exposure. Toxicology is the science that experimentally investigates the occurrence, nature, mechanism, and risk factors for the adverse effects of toxic substances. Toxicants : substances that produce adverse biological effects of any nature may be chemical or physical in nature effects may be of various types (acute, chronic) Toxins: specific proteins produced by living organisms Poisons: toxicants that cause immediate death or illness when experienced in very small amounts effects of chemicals or physical agents on living of the adverse  Acute Toxicity ❑Acute Toxicity: involves harmful effects in an organism through a single or short – term exposure. An example would be chemical asphyxiation from exposure to a high concentration of carbon monoxide. ❑ Acute toxicity (single dose or < 24h) Acute toxicity (single dose or < 24h) ƒ may lead to immediate (“acute”) effects  Chronic Toxicity ❑ Chronic Toxicity: The ability of a substance or mixture of substances to cause harmful effects over an extended period, usually upon repeated or continuous exposure. An example would be the development of silicosis following a long – term exposure to silica in workplaces as foundries. Chronic toxicity (repeated doses) Chronic toxicity (repeated doses) may lead to sudden (“acute”) effects results from accumulation of toxic agent or from cumulative effects may lead to delayed or persistent (“chronic”) effects  Major factors that influence toxicity Duration & The patient’s Route of frequency of age, sex administration. exposure. Dose or The properties concentration. of the toxicant Rapidity of response with respect to route of exposure Intravenous Inhalation Intraperitoneal Subcutaneous Intramuscular Intradermal. Topical Most frequently influenced organs: Liver Kidney Brain intestine Lung, and other  Undesired effects Allergic reactions. Immediate and Delayed toxicity. Reversible + Irreversible toxicity. Local and Systemic toxicity.  Toxicity can result from adverse cellular, biochemical, or macromolecular changes. Examples are: - cell replacement, such as fibrosis – damage to an enzyme system – disruption of protein synthesis – production of reactive chemicals in cells – DNA damage  LD50 : MEDIAN LETHAL DOSE: LD 50 is the amount of a material, given all at once, LD stands for “Lethal Dose”. which causes the death of 50% of a group of test animals. The LD 50 is one way to measure the short-term poisoning (acute toxicity) of The lower the LD 50 dose, a material. It is an index the more toxic the substance. determination of medicine and poison’s virulence. (ED50) : Effective dose means the concentration of a drug at which 50% of a population of patients are effectively treated. This could be determined in an experiment which is similar to that described for LD50.  The therapeutic index. ED50 and LD50 are useful in determination of the therapeutic index. This entity is merely the LD50 divided by the ED50