Toxicology Introduction Overview

Toxicodynamics Biological effects caused by a toxin binding to a biological target Pharmacodynamics Study of what drugs do to the body and how they do it Toxicological effects Effects of toxins on living organisms Receptor Molecular component recognizing and binding drugs or hormones eliciting a cellular response Dose-effect relationship Correlation between drug dosage and its effects Time-effect relationship Correlation between time and drug effects Structure-activity relationship Relationship between chemical structure of a drug and its biological activity Target Sites Locations where drugs/toxins bind in the body Ionotropic Receptors that function as ion channels Metabotropic Receptors that activate signal transduction pathways Transporter Proteins moving molecules across cell membranes Affinity Strength of binding between a drug and its receptor Intrinsic activity Ability of a drug-receptor complex to produce an effect Agonists Drugs activating receptors to signal Antagonists Drugs binding to receptors without activating a signal what determines whether and with affin- The molecular size, shape, and electrical ity a drug binds to a receptor charge changes in the chemical structure of a can dramatically increase or decrease a drug new drug's affinities for different classes 1/4 of receptors, with resulting alterations in therapeutic and toxic effects the concentration of drug required to The receptor's affinity for binding a drug form a significant number of drug-recepdetermines tor complexes what are receptors made from Most receptors are proteins with various functions action means the primary action of the drug on the body effect means the functional or morphological alteration of the body induced by drugs. Excitation Strengthening the original function of the body Inhibition Weakening the original function of the body Stimulant Drug that strengthens the original function of the body Depressant Drug that weakens the original function of the body drugs cannot create effects only altering the rate at which any bodily function proceeds e it may excite some organ and inhibit a drug being a depressant and stimulant another one, even if the same tissue of means different organs . Effected by dosage of drug and condition of body Selectivity of Drug Action Characteristic effects on a select tissue or organ in a given dose but not on another Acetylcholinesterase cholinergic Enzyme breaking down acetylcholine into acetic acid and choline Organophosphorus Poisons Toxic substances interacting with AChE similar to acetylcholine Carbamate Poisons Toxic substances binding strongly to AChE active site 2/4 Therapeutic Effect Desired outcome of drug therapy curing or suppressing disease Adverse Reaction Unwanted, harmful effects of drug therapy Etiological Treatment Primary therapy eliminating the disease Symptomatic Treatment Treatment to suppress symptoms without curing the disease Side Effects Undesired effects occurring at therapeutic doses Toxic Reaction Adverse reactions due to overdose or long-term use Residual Effect Biological responses post-drug cessation below effective levels Withdrawal Reaction Worsening of original disease after stopping drug Unusual Reaction Unpredictable adverse reaction unrelated to drug action Idiosyncrasy Genetically determined abnormal reactivity to a drug Allergy Adverse reaction from previous sensitization to a drug Potency Measure of how much drug is needed to elicit a response Efficacy Maximal response produced by a drug Minimal Toxic Dose Dosage likely to produce minimal toxicity Maximal Effective Dose Maximum dose used in patients as per Pharmacopoeias Usual Dose Safe and effective dose for most patients EC50 Concentration producing 50% of maximal drug effect Graded Dose-Response Relation Comparison of drug potencies and efficacies using dose-effect curve 3/4 Competitive antagonist Inhibits agonist response by competing for binding Irreversible antagonist Binds irreversibly, reducing available receptors Quantal dose-response Characterizes drug potency and selectivity ed50 (effective dose) , the dose at which 50% of individuals exhibit the specified quantal effect TD50 (toxic dose), the dose required to produce a particular toxic effect in 50% of animals. LD50 (lethal dose), the dose required to produce the death in 50% of animals. Therapeutic index (TI) Ratio of LD50 to ED50 for drug safety Therapeutic Window Safe, effective drug dose range with minimal side effects Time for onset action (latent period): a delay in time before the first signs of drug effect are manifested following the administration of a drug, the duration of action of a drug extends from the moment of onset of perceptible . Duration of action (persistent period) effects to the time when an action can no longer be measured. the duration from the time when an action Residue period: can no longer be measured to the time when the drugs are eliminated. MEC Minimum effective concentration of a drug MSC Minimum safe concentration of a drug Clark's rule Equation for pediatric medication dosage based on weight Weight kg divided by 68 kg) x Adult Dose recommended = Pediatric Dosage 4/4