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FACTORS AFFECTING DRUG ACTIVITY
Adapted from the Pharmacy Technician, 6th Edition Jessica Tagerman, pharmD, Rph © 2016 Perspective Press/Morton Publishing Company
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© 2016 Perspective Press/Morton Publishing Company
Human Variability Age Gender Pregnancy Genetics Body Weight Psychological Factors Neonates & Infants Slower drug distribution, metabolism, excretion Children Metabolize certain drugs more rapidly than adults Elderly Slower absorption, distribution, metabolism, excretion Gender Pregnancy Genetics pharmacogenomics Body weight children obese adults Psychological factors placebo effect © 2016 Perspective Press/Morton Publishing Company
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Adverse Drug Reactions
Undesired patient-specific effects common or rare localized or widespread mild or severe “side effects” Some occur at normal doses, others more likely at elevated doses Hypersensitivity/allergy anaphylactic shock Idiosyncrasy unexpected reaction Carcinogenicity ability of substance to cause cancer © 2016 Perspective Press/Morton Publishing Company
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Adverse Drug Reactions, cont’d
Teratogenicity ability of substance to cause abnormal fetal development analgesics, diuretics, antihistamines, antibiotics, anti-emetics Hepatotoxicity affects liver acetaminophen, isoniazid, nitrofurantoin Nephrotoxicity affects kidneys aminoglycosides, NSAIDs © 2016 Perspective Press/Morton Publishing Company
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Adverse Drug Reactions, cont’d
Hematological effects bleeding, bone marrow disorders anticoagulants, antineoplastics Gastrointestinal effects anorexia, nausea, vomiting, constipation, heartburn, diarrhea anti-inflammatories Central nervous system effects stimulation: agitation, disorientation depression: dizziness, drowsiness, coma efavirenez, antimalarial drugs, amantadine © 2016 Perspective Press/Morton Publishing Company
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Adverse Drug Reactions, cont’d
Drug dependence physiological and/or psychological narcotic analgesics, sedative hypnotics, antianxiety agents, amphetamines Tolerance over-adaptation to drug increase dose narcotics Resistance reduction of an antibiotic’s effectiveness use different drug © 2016 Perspective Press/Morton Publishing Company
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Drug-Drug Interactions
One drug affects another’s disposition absorption, distribution, metabolism, excretion One drug affects another’s access to receptors or interferes with physiological processes (interactions at site of action) additive effects, synergism, potentiation, antagonistic interaction (antidote) Absorption complexation gastric emptying gastric pH intestinal metabolism Distribution displacement one drug removes another from a plasma protein binding site significant if percent bound is high Metabolism enzyme induction increases metabolism of drugs using same enzymes reduces pharmacological effect enzyme inhibition drugs compete for binding sites on same enzymes increases pharmacological effect Excretion changes in glomerular filtration rate in response to specific drugs drugs compete for renal secretory system causing drug to accumulate in blood urinary reabsorption altered by changes in pH from base/acidic drugs © 2016 Perspective Press/Morton Publishing Company
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Drug-Drug Interactions
Additive effects two drugs cause an effect = sum of individual effects trimethoprim + sulfamethoxazole Synergism two drugs cause an effect greater than the sum of individual effects aspirin + warfarin Potentiation a drug with no activity of its own increases another drug’s activity to produce an effect amoxicillin + clavulanic acid Antidote blocks or reduces another drug’s toxic effect naloxone + morphine © 2016 Perspective Press/Morton Publishing Company
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Drug-Diet Interactions
Chemical interactions Improved solubility of some drugs Performance of dosage form Effects of Dietary Factors on Metabolism Change in Food Composition Effect on Metabolism Increased Protein Increased Metabolism Increased Carbohydrates Decreased Metabolism Increased Fat No effect Decreased Calories © 2016 Perspective Press/Morton Publishing Company
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© 2016 Perspective Press/Morton Publishing Company
Questions? © 2016 Perspective Press/Morton Publishing Company
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