Pharmacokinetics and Pharmacodynamics PDF

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https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.saga.c o.uk%2Fmagazine%2Fhealth- wellbeing%2Ftreatments%2Fmedicines%2Fdrug- PHARMACOKINETICS interactions&psig=AOvVaw26gAswFxGzmCA_66ZF7Y8s&ust=1610 031995487000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCOC P_9vKh-4CFQAAAAAdAAAAABAO PHARMACODYNAMICS DRUG INTERACTION Prepared By: Ms. Emily Jane Filler- Carreon RN MAN https://www.google.com/url?sa=i&url=https%3A%2F%2Fsouthfloridareporter.com%2Fthe-all-in-one- guide-to-drug- interactions%2F&psig=AOvVaw26gAswFxGzmCA_66ZF7Y8s&ust=1610031995487000&source=image s&cd=vfe&ved=0CAIQjRxqFwoTCOCP_9vKh-4CFQAAAAAdAAAAABAI PRINCIPLES OF DRUG ACTION AND DRUG INTERACTION Pharmacokinetics https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww. pepid.com%2Fintegration%2Fdrug- interactions.asp&psig=AOvVaw12Dr- qN2ifucgSokDK5t90&ust=1610032849981000&source=image Pharmacodynamics s&cd=vfe&ved=0CAIQjRxqFwoTCIDO4vTNh- 4CFQAAAAAdAAAAABAD Pharmacogenetics https://www.google.com/url?sa=i&url=htt ps%3A%2F%2Fwww.publichealth.com. ng%2Fhow-to-check-for-drug- interactions%2F&psig=AOvVaw12Dr- https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.shutter qN2ifucgSokDK5t90&ust=16100328499 Drug Interaction stock.com%2Fsearch%2Fdrug%2Binteraction&psig=AOvVaw12Dr- qN2ifucgSokDK5t90&ust=1610032849981000&source=images&cd=v 81000&source=images&cd=vfe&ved=0 CAIQjRxqFwoTCIDO4vTNh- fe&ved=0CAIQjRxqFwoTCIDO4vTNh-4CFQAAAAAdAAAAABAJ 4CFQAAAAAdAAAAABAP Pharmacokinetics Is the process of drug movement throughout the body that is necessary to achieve drug action. The four processes are absorption, distribution, metabolism (or biotransformation), and excretion (or elimination). Pharmacokinetics Drug Absorption The movement of the drug into the bloodstream after administration. Enteral Drugs Drugs Given Drugs Given Drugs Given (By Mouth) Intramuscularly Subcutaneously Rectally Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) Most oral drugs enter the bloodstream following absorption across the mucosal lining of the small intestine The epithelial lining of the small intestine is covered with villi, finger like protrusions that increase the surface area available for absorption. Absorption is reduced if the villi are decreased in number because of disease, drug effect, or the removal of some or all of the small intestine. Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) Following absorption of oral drugs from the GI tract, they pass from the intestinal lumen to the liver via the portal vein. In the liver, some drugs are metabolized to an inactive form and are excreted, thus reducing the amount of active drug available to exert a pharmacologic effect. This is referred to as the first-pass effect or first-pass metabolism. Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) Absorption across the mucosal lining of the small intestine occurs through: 1. Passive Transport 2. Active Transport 3. Pinocytosis Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) Absorption across the mucosal lining of the small intestine occurs through: drugs move across the cell membrane from an area of Diffusion higher concentration to one of lower concentration. 1. Passive Transport -does not require energy to move drugs across the membrane. relies on a carrier protein to move the drug from an area of Facilitated Diffusion higher concentration to an area of lower concentration. Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) McCuistion, L. etal. Pharmacology: A Patient- Centered Nursing Process Approach, 9th ed p. 66 Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) Absorption across the mucosal lining of the small intestine occurs through: requires a carrier, such as an 2. Active Transport enzyme or protein, to move the drug against a concentration gradient. McCuistion, L. etal. Pharmacology: A Patient- Centered Nursing Process Approach, 9th ed p. 66 Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) Absorption across the mucosal lining of the small intestine occurs through: Is a process by which cells carry a drug across their 3. Pinocytosis membrane by engulfing the drug particles in a vesicle. Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) -Dissolution For the body to utilize drugs taken by mouth, a drug in solid form (e.g., tablet or capsule) must disintegrate into small particles and =https%3A%2F%2Fbiorelevant.com% combine with a liquid to form a solution, a process known as https://www.google.com/imgres?imgurl 2Fsite_upload_media%2Fmeta_image s%2Fdisintegration.png&imgrefurl=http dissolution (drugs in liquid form are already in solution), in order s%3A%2F%2Fbiorelevant.com%2Flea rning_center%2Fdisintegration- dissolution%2F&tbnid=kyWgDQalXxFr to be absorbed from the gastrointestinal (GI) tract into the YKHctBBUgQMygVegUIARDnAQ..i&d bloodstream. nM&vet=12ahUKEwjyhMepz4fuAhXlIa ocid=DCSZEGq3VYurCM&w=1220&h= 921&q=drug%20dissolution&ved=2ah UKEwjyhMepz4fuAhXlIaYKHctBBUgQ MygVegUIARDnAQ Tablets are not 100% drug. Fillers and inert substances— such as simple syrup, vegetable gums,aromatic powder, honey, and https://www.google.com/url?sa=i &url=https%3A%2F%2Fwww.sci encedirect.com%2Fscience%2F various elixirs— called excipients are used in drug preparation to article%2Fpii%2FS0378517313 003451&psig=AOvVaw1a0bDlD allow the drug to take on a particular size and shape and to 1YVJ6AGc1WKhckg&ust=1610 033234780000&source=images enhance drug dissolution. &cd=vfe&ved=0CAIQjRxqFwoT CODGhOHPh- 4CFQAAAAAdAAAAABAD Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) - Disintegration https://www.google.com/imgres?imgurl =https%3A%2F%2Fbasicmedicalkey.c Disintegration is the breakdown of an oral drug into smaller om%2Fwp- content%2Fuploads%2F2016%2F09% particles. The rate of dissolution is the time it takes the drug to 2FA321497_1_En_3_Fig3_HTML.gif&i mgrefurl=https%3A%2F%2Fbasicmedi disintegrate and dissolve to become available for the body to calkey.com%2Fdrug-absorption-and- bioavailability%2F&tbnid=KsgQ- absorb it. Generally, drugs are both disintegrated and absorbed faster in acidic fluids with a pH of 1 or 2 rather than in alkaline 4VNGimkVM&vet=12ahUKEwivrbWF0If uAhUPHKYKHX5ABiMQMygfegUIARC BAg..i&docid=TgroDW8Xkp5ajM&w=55 3&h=234&q=drug%20disintegration&ve d=2ahUKEwivrbWF0IfuAhUPHKYKHX fluids (those with a pH greater than 7). 5ABiMQMygfegUIARCBAg https://www.google.com/imgres?img url=https%3A%2F%2Fwww.intertek.c om%2FuploadedImages%2Fwwwint ertekcom%2FIndustries%2FFood_an d_Healthcare%2F_Images%2FPhar Enteric-coated (EC) drugs resist disintegration in the gastric ma%2FStabilityDissolution.jpg%3Fn %3D3758&imgrefurl=https%3A%2F acid of the stomach, so disintegration does not occur until the drug reaches the alkaline environment of the small intestine. %2Fwww.intertek.com%2Fpharmace utical%2Fgmp-cmc- laboratory%2Fpharmaceutical- dissolution- testing%2F&tbnid=54uWT0UxdDdB wM&vet=12ahUKEwivrbWF0IfuAhUP HKYKHX5ABiMQMyhfegUIARCnAQ..i&docid=myg2hdvZL_VYgM&w=760 &h=192&q=drug%20disintegration&v ed=2ahUKEwivrbWF0IfuAhUPHKYK HX5ABiMQMyhfegUIARCnAQ Pharmacokinetics- Drug Absorption FOR DRUGS TAKEN BY MOUTH (ENTERAL) - Bioavailability Refers to the percentage of administered drug available for activity. For orally administered drugs, bioavailability is affected by https://www.google.com/url?sa=i& url=https%3A%2F%2Fm.youtube. absorption and first-pass metabolism. The bioavailability of oral com%2Fwatch%3Fv%3Dadb7Cc C_Ch4&psig=AOvVaw0jRrYj7B2L drugs is always less than 100% and varies based on the rate of KReoo5vdlsuE&ust=1610033615 616000&source=images&cd=vfe& first-pass metabolism ved=0CAIQjRxqFwoTCIjM5OHQh -4CFQAAAAAdAAAAABAD Factors that alter bioavailability https://www.google.com/imgres?i mgurl=https%3A%2F%2Fi.ytimg.c 1. Drug Form om%2Fvi%2Fadb7CcC_Ch4%2F maxresdefault.jpg&imgrefurl=https 2. Route of administration %3A%2F%2Fm.youtube.com%2F watch%3Fv%3Dadb7CcC_Ch4&t bnid=WLXSywKS0rFbXM&vet=12 3. Gastric Mucosa and Motility ahUKEwjyuZPf0IfuAhUMY5QKHT r6BLcQMygEegUIARDYAQ..i&do 4. Administration with food and other drugs cid=7n7VVu- hFejAYM&w=1280&h=720&q=bio availability&ved=2ahUKEwjyuZPf0 5. Changes in the liver function IfuAhUMY5QKHTr6BLcQMygEeg UIARDYAQ Pharmacokinetics- Drug Absorption FACTORS THAT AFFECT ABSORPTION Blood Flow Fasting Pain Food Stress pH Hunger Exercise Pharmacokinetics- Drug Absorption DRUGS GIVEN Intramuscularly https://www.google.com/imgres?imgurl=https%3A% 2F%2Fassets.aboutkidshealth.ca%2Fakhassets%2 _ILL_EN.jpg%3FRenditionID%3D10&imgrefurl=http s%3A%2F%2Fwww.aboutkidshealth.ca%2FArticle Are absorbed faster in muscles that have increased blood flow FInjection_intramuscular_BDsyringe_layers_EQUIP %3Fcontentid%3D997%26language%3DEnglish&tb nid=Wp9vzt6GgI5qWM&vet=12ahUKEwjz0IXI0YfuA hXIAaYKHTbLAyQQMygCegUIARCpAQ..i&docid=t 1SMHU2s6AOf5M&w=356&h=267&q=intramuscula r%20drug&ved=2ahUKEwjz0IXI0YfuAhXIAaYKHTb LAyQQMygCegUIARCpAQ DRUGS GIVEN Subcutaneously Subcutaneous tissue has decreased blood flow when compared https://www.google.com/imgres?imgurl=https%3A with muscle, so absorption is slower when drugs are given subcutaneously. %2F%2Fcdn.ps.emap.com%2Fwp- content%2Fuploads%2Fsites%2F3%2F2018%2F0 8%2Ffig-1Ttissue-structure-and-subcutaneous- However, drugs that are given subcutaneously have a more rapid injection_660.jpg&imgrefurl=https%3A%2F%2Fww w.nursingtimes.net%2Fclinical- archive%2Fassessment-skills%2Finjection- and predictable rate of absorption than those given by mouth. technique-2-administering-drugs-via-the- subcutaneous-route-28-08- 2018%2F&tbnid=EcM829mSCUH8yM&vet=12ahU KEwiV9OyS0ofuAhUIHqYKHV3UDxYQMygBegUI ARCoAQ..i&docid=eDQWtWK50HzdRM&w=660&h =718&q=subcutaneous%20drug&ved=2ahUKEwiV 9OyS0ofuAhUIHqYKHV3UDxYQMygBegUIARCoA Q Pharmacokinetics- Drug Absorption DRUGS GIVEN Rectally Are absorbed slower than drugs administered by the oral route. https://www.google.com/imgres?imgurl=https%3A %2F%2Fupload.wikimedia.org%2Fwikipedia%2Fc Absorption is slower because the surface area in the rectum is smaller than the stomach, and it has no villi. ommons%2Fc%2Fc6%2FAdministering-med- rectally- 2.png&imgrefurl=https%3A%2F%2Fen.wikipedia.o rg%2Fwiki%2FRectal_administration&tbnid=DSqG f2KKYL- IYM&vet=12ahUKEwj1jZzN0ofuAhVSBaYKHZ4dD eQQMygAegUIARClAQ..i&docid=EMjUjYEeSRcN TM&w=758&h=535&q=rectal%20drug&ved=2ahU KEwj1jZzN0ofuAhVSBaYKHZ4dDeQQMygAegUIA RClAQ Pharmacokinetics Drug Distribution The movement of the drug from the circulation to body tissues Drug Distribution is influenced by: Rate of Drugs Protein Flow to Affinity to Binding the tissue the tissue Pharmacokinetics PROTEIN BINDING As drugs are distributed in the plasma, many bind with plasma proteins (albumin, lipoproteins,and alpha-1-acid-glycoprotein [AGP]). Acidic drugs such as aspirin and methotrexate and neutraldrugs such as nortriptyline bind with albumin or lipoproteins; however, basic drugs (morphine,amantadine) bind to AGP. Drugs that are more than 90% bound to protein are known as highly protein-bound drugs Example: Warfarin, Glyburide, Sertraline, Furosemide, and Diazepam Pharmacokinetics PROTEIN BINDING The portion of the drug bound to protein is inactive because it is not available to interact with tissue receptors and therefore is unable to exert a pharmacologic effect The portion that remains unbound is free, active drug. Free drugs are able to exit blood vessels and reach their site of action, causing a pharmacologic response. Pharmacokinetics PROTEIN BINDING Low plasma protein levels Potentially decrease the number of available binding sites and can lead to an increase in the amount of free drug available, resulting in drug accumulation and toxicity. Blood vessels in the brain have a special endothelial lining where the cells are pressed tightly together (tight junctions); this lining is referred to as the blood-brain barrier (BBB). The BBB protects the brain from foreign substances, which includes about 98% of the drugs on the market. Some drugs that are highly lipid soluble and of low molecular weight (e.g., benzodiazepines) are able to cross the BBB through diffusion, and others cross via transport proteins. Water-soluble drugs (e.g., atenolol and penicillin) and drugs that are not bound to transport proteins (free drugs) are not able to cross the BBB, which makes it difficult for these drugs to reach the brain Pharmacokinetics PROTEIN BINDING Low plasma protein levels Potentially decrease the number of available binding sites and can lead to an increase in the amount of free drug available, resulting in drug accumulation and toxicity. Blood vessels in the brain have a special endothelial lining where the cells are pressed tightly together (tight junctions); this lining is referred to as the blood-brain barrier (BBB). The BBB protects the brain from foreign substances, which includes about 98% of the drugs on the market. Some drugs that are highly lipid soluble and of low molecular weight (e.g., benzodiazepines) are able to cross the BBB through diffusion, and others cross via transport proteins. Water-soluble drugs (e.g., atenolol and penicillin) and drugs that are not bound to transport proteins (free drugs) are not able to cross the BBB, which makes it difficult for these drugs to reach the brain Pharmacokinetics Drug Metabolism/ Biotransformation The process by which the body chemically changes drugs into a form that can be excreted. Pharmacokinetics DRUG METABOLISM The liver is the primary site of metabolism. Liver enzymes—collectively referred to as the cytochrome P450 system, or the P450 system, of drug-metabolizing enzymes—convert drugs to metabolites. A large percentage of drugs are lipid soluble, thus the liver metabolizes the lipid-soluble drug substance to a water-soluble substance for renal excretion. Pharmacokinetics DRUG METABOLISM The drug half-life (t½) is the time it takes for the amount of drug in the body to be reduced by half. The amount of drug administered, the amount of drug remaining in the body from previous doses, metabolism, and elimination affect the half-life of a drug. A drug goes through several half-lives before complete elimination occurs, and drug half-life is used to determine dosing interval. Pharmacokinetics DRUG METABOLISM By knowing the half-life, the time it takes for a drug to reach a steady state (plateau drug level)can be determined. A steady state occurs when the amount of drug being administered is the same as the amount of drug being eliminated; a steady state of drug concentration is necessary to achieve optimal therapeutic benefit. This takes about four half-lives, if the size of all doses is the same. Pharmacokinetics DRUG METABOLISM However, in the case of drugs with long half-lives, it may not be acceptable to wait for a steady state to be achieved. By giving a large initial dose, known as a loading dose, that is significantly higher than maintenance dosing, therapeutic effects can be obtained while a steady state is reached. Pharmacokinetics Drug Excretion The process of elimination of drugs from the body Pharmacokinetics The main route of drug excretion, elimination of drugs from the body, is through the kidneys. Drugs are also excreted through bile, the lungs, saliva, sweat, and breast milk. The kidneys filter free drugs (in healthy kidneys, drugs bound to protein are not filtered), water-soluble drugs, and drugs that are unchanged. Pharmacokinetics FACTORS THAT AFFECT DRUG EXCRETION Prerenal Intrarenal Post Renal Urine pH conditions conditions conditions Acidic urine Reduce blood Affect Adversely promotes flow to the glomerular affect elimination of filtration and weak base drugs kidney and glomerular result in tubular filtration decreased secretion and Alkaline urine glomerular reabsorption. promotes filtration. elimination of weak acid drugs Pharmacokinetics COMMON TESTS TO DETERMINE RENAL FUNCTION 1. Creatinine 2. Blood Urea Nitrogen a metabolic by- the metabolic product of muscle that breakdown product of is excreted by the protein metabolism. kidneys Pharmacodynamics The study of the effects of drugs on the body A drug’s primary effect is the desirable response The secondary effect may be desirable or undesirable Pharmacodynamics a drug with low potency, such as Potency refers to codeine, produces minimal therapeutic the amount of drug responses at low concentrations. needed to elicit a A drug with high potency, such as specific physiologic fentanyl, produces significant response to a drug. therapeutic responses at low concentrations Dose-response Maximal efficacy relationship The point at which -the body’s increasing a drug’s physiologic dosage no longer response to increases the desired changes in drug therapeutic response concentration at the site of action. -Describes the relationship between the therapeutic TD50 is the dose of a drug that Closely related dose of a drug (ED50) and produces a toxic response in 50% of to dose- the toxic dose of a drug the population. response and (TD50). efficacy is the - The therapeutic index is ED50 is the dose of a drug that therapeutic produces a therapeutic response in the difference between these index (TI) 50% of the population two points Pharmacodynamics  Pharmacodynamics Duration Onset Peak of action the time it takes occurs when it the length of time for a drug to reaches its the drug exerts a reach the highest therapeutic effect. minimum effective concentration in concentration the blood. (MEC) after administration. Pharmacodynamics THERAPEUTIC DRUG MONITORING Plasma Drug The highest plasma concentration of drug at a specific time, and it Level indicates the rate of drug absorption If the drug is given orally, the peak time is usually 2 to 3 hours after drug administration. If the drug is given intravenously, the peak time is usually 30 to 60 minutes after the infusion is complete If the drug is given intramuscularly, the peak time is usually 2 to 4 hours after injection Pharmacodynamics THERAPEUTIC DRUG MONITORING Trough drug The lowest plasma concentration of a drug, and it level measures the rate at which the drug is eliminated. Trough levels are drawn just prior to the next dose of drug regardless of route of administration. Pharmacodynamics RECEPTOR THEORY Most receptors, which are protein in nature, are found on cell surface membranes or within the cell itself. The four receptor families: G protein–coupled Transcription factors Cell membrane–embedded receptor systems. Found in the cell nucleus on Ligand-gated ion channels. enzymes. The three components to DNA, not on the surface. The channel crosses the Activation of The ligand-binding domain this receptor response are cell membrane. When the receptorsthrough for drug binding is on the (1) the receptor, (2) the G channel opens, ionsflow transcription factors cellsurface. The drug protein that binds with regulates protein synthesis into and out of the cells. activates the enzyme guanosine triphosphate and is prolonged. With the This primarily affects inside the cell, and a (GTP), and (3) the effector, first threereceptor groups, sodium and calcium ions. response is initiated. which is either an enzyme activation of the receptors is or an ion channel. rapid. Pharmacodynamics AGONISTS ANTAGONISTS Drugs that activate Drugs that prevent receptors and receptor activation produce a desired and block a response response Pharmacodynamics Nonspecific and Nonselective Drug Effects Nonspecific Nonselective Drugs that affect multiple receptor sites Drugs affect multiple receptors Example: Bethanechol may be prescribed Example: Epinephrine, which is used for for postoperative urinary retention to treatment of anaphylaxis or severe increase bladder contraction. This drug asthma exacerbations, acts on thealpha1, stimulates cholinergic receptors located beta1, and beta2 receptors affecting in the bladder, and urination occurs by multiple body systems strengthening bladder contraction. However, because bethanecho lis nonspecific, other cholinergic sites are also affected: the heart rate decreases, blood pressure decreases, gastric acid secretion increases. Pharmacodynamics Nonspecific and Nonselective Drug Effects Nonspecific Nonselective Drugs that affect multiple receptor sites Drugs affect multiple receptors Example: Bethanechol may be prescribed Example: Epinephrine, which is used for for postoperative urinary retention to treatment of anaphylaxis or severe increase bladder contraction. This drug asthma exacerbations, acts on thealpha1, stimulates cholinergic receptors located beta1, and beta2 receptors affecting in the bladder, and urination occurs by multiple body systems strengthening bladder contraction. However, because bethanechol is nonspecific, other cholinergic sites are also affected: the heart rate decreases, blood pressure decreases, gastric acid secretion increases. Pharmacodynamics 1. Stimulation A drug that stimulates enhances intrinsic activity (e.g., adrenergic drugs that increase heart rate) 2. Depression Depressant drugs decrease neural activity and bodily functions (e.g., barbiturates and opiates) Mechanisms of Drug Action 3. Irritation Drugs that irritate have a noxious effect, such as astringents. 4. Replacement Replacement drugs such as insulins, thyroid drugs, and hormones replace essentialbody compounds. 5. Cytotoxic Cytotoxic drugs selectively kill invading parasites or Action cancers Pharmacodynamics 6. Antimicrobial Medication Antimicrobial drugs prevent, inhibit, or kill Mechanisms of infectious organisms. Drug Action 7. Modification Drugs that modify immune status modify, enhance, of immune or depress the immune system (e.g., interferons and system methotrexate) Pharmacodynamics Secondary effects of drug therapy. All drugs have side effects. n some instances, the side effects may be desirable (e.g., using SIDE diphenhydramine at bedtime, when its side EFFECTS effect of drowsiness is beneficial). Side Effects, Chronic illness, age, weight, gender, and Adverse Drug ethnicity all play a part in drug side effects. Reactions, Drug Toxicity Unintentional, unexpected reactions to drug ADVERSE therapy that occur at normal drug dosages. DRUG Adverse drug reactions are always REACTIONS undesirable and must be reported Pharmacodynamics Occurs when drug levels exceed the Side Effects, therapeutic range; toxicity may occur DRUG secondary to overdose (intentional or Adverse Drug TOXICITY unintentional) or drug accumulation. Reactions, Drug Toxicity Factors that influence drug toxicity include disease, genetics, and age. Pharmacogenetics Refers to the study of genetic factors that influence an individual’s response to a specific drug. Genetic factors can alter drug metabolism Pharmacogenetics Biologic Pharmacogenomics refers to the study of how Variation genetics play a role in a person’s response to drugs (absorption, distribution, metabolism, and excretion). The use of pharmacogenomics, the goal is to develop precision medicine, which uses the person’s genetic makeup to determine appropriate drug therapy, thereby improving patient outcomes and safety Certain classifications of medications have different effects in individuals with specific genetic markers. Pharmacogenetics Placebo Tolerance Tachyplaxis refers to an acute, refers to a rapid decrease in Effect drug response not decreased response to a drug; attributed to the responsiveness to a it may occur after chemical properties drug over the the first dose or of the drug. course of therapy after several doses Drug Interactions Defined as an altered or modified action or effect of a drug as a result of interaction with one or multiple drugs. CATEGORIES: →Pharmacokinetic interactions are changes that occur in the absorption, distribution, metabolism, and excretion of one or more drugs. →Pharmacodynamic interactions are those that result in additive, synergistic, or antagonistic drug effects. Drug Interactions Synergistic Drug Antagonistic Drug Additive Drug Effect Effects and Effects Potentiation When two drugs are administered in combination, and the response is increased beyond what either The clinical One drug reduces could produce alone effect of the or blocks the effect two drugs given of the other. The sum of the effects of together is the two drugs. substantially greater than Antagonistic effects Can be desirable or that of either are desirable undesirable. drug alone. Drug Interactions Drug- Drug The most common symptoms of drug-drug interactions include nausea, heartburn, Interaction headache, and lightheadedness. Drug- Food may increase, decrease, or delay the Nutrient body’s pharmacokinetic response to drugs. Interaction Drug- Drugs often interfere with clinical laboratory testing by cross-reaction with antibodies, Laboratory interference with enzyme reactions, or Interaction alteration of chemical reactions Drug Interactions Drug- Induced Photosensitivity Reaction- a skin reaction caused by exposure to sunlight. It is caused most often by the interaction of a drug and exposure to ultraviolet A (UVA) light 1. Photoallergic reaction -occurs when a drug undergoes 2. Phototoxic reaction activation in the skin by ultraviolet - a photosensitive drug undergoes light to a compound that is more photochemical reactions within the allergenic than the parent compound. skin to cause damage. - a type of delayed hypersensitivity - type of reaction is not immune reaction. mediated. -is not related to drug dose and only - may be the result of the drug dose requires previous exposure, or sensitization, to the offending agent. Drug Interactions Examples of Drugs that induced Photosensitivity Reference: