Drug Response & Interactions PDF

Idiosyncrasy - Unusual drug Response caused by genetic differences in metabolism of the drug or by immunologic mechanisms, including allergic reactions. Hyporeactivity - the intensity of effect of a given dose of drug is diminished Hyperreactivity- the intensity of effect of a given dose of...

Idiosyncrasy - Unusual drug Response caused by genetic differences in metabolism of the drug or by immunologic mechanisms, including allergic reactions. Hyporeactivity - the intensity of effect of a given dose of drug is diminished Hyperreactivity- the intensity of effect of a given dose of drug is increased in comparison to the effect seen in most individuals. Hypersensitivity -refers to allergic or other immunologic responses to drugs TYPE OTHER NAM NAMES MES I Allergyy (Immediate) (Immediate) II Cytotoxic, Cytotoxxic, Antibody dependent dep pendent III Immune ne Complex Immun Complex Disease e IV Delayed-Type Hy Hypersensitivity ypersensitivity V Autoimmune Aut Disease toimmune Dis sease Tolerance - it refers to a decreased responsiveness to the drug a consequence of continued drug administration Tachyphylaxis- This refers to rapidly acting tolerance Responsiveness diminishes rapidly after administration of a drug Alterations in Number or Function of Receptors Down-regulation of receptors ‰ it is caused by continuous prolonged exposure of receptors to drugs that disrupt the homeostatic equilibrium and result in altered levels of the receptors. Desensitization ‰ It is the result of down-regulation. ‰ The target cells become desensitized, and the effect of subsequent exposure to the same concentration of the drug is reduced. Classification of drugs according to receptor interaction 1. AGONIST ‰ Able to bind (with affinity) ‰ With intrinsic activity 1.1 Full agonist ‰ Full response ‰ Stimulate all different variant of receptors even the new receptors 1.2 Partial agonist ‰ Less than the expected response 2. ANTAGONIST ƒ With affinity but no intrinsic activity ƒ It prevents the binding of agonist Antagonist Antago onist Recept Receptor tor Antagonist-Receptor Antagon nist-Recepto or DENIED! DENIED!! Complex Comple ex PHARMACOLOGIC ANTAGONIST ‰ utilizes the same receptor ‰ produce an effect opposite of agonist by binding to the same receptor ‰ Beta blocker and Beta agonist (Propranolol) (epinephrine) PHYSIOLOGIC ANTAGONIST - occurs when the drugs act independently at different receptor sites, often yielding opposing actions. e.g. HISTAMINE + EPINEPHRINE CHEMICAL ANTAGONIST ‰ no receptor is involved ‰ occurs when two drugs bind with each other to form an inactive compound. Protamine SO4 + Heparin SO4 o forms a complex devoid of action Protamine- (+) charged at physiologic pH Heparin ± (-) charged at physiologic pH Chelating agents Deferoxamine ± Iron (Fe) It depends on whether or not they reversibly compete with agonists for binding to receptors Competitive antagonist- Effects of Antagonist can be overcome/reversed by increasing the concentration of agonist  NO RESPONSE NON-COMPETITIVE ANTAGONISM it is also known as irreversible antagonism 1. ADDITION ‰ A drug effect that is equal in the magnitude to the sum of the individual effects of two drugs. ‰ Two different drugs with the same effect are given together. ‰1 +1=2 ‰ Alcohol + Sedative hypnotic drug 2. SYNERGISM ‰ The effect of two drugs is greater in magnitude than the sum of the individual effects of the two drugs. ‰ Two drugs with same effect are given together. ‰1 +1=3 ‰ Sulfamethoxazole + Trimethoprim 3. POTENTIATION ‰ Occurs when one drug, lacking an effect of its own, increases the effect of another drug that is active. ‰1 + 0 = 2 ‰ Tyramine-containing Foods + MAOI