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Drug
any chemcial that can affect living process
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Pharmacology
- study of drugs and their interactions with living systems
- physical chemical properties/biochemical physiologic effects
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Clinical Pharmacology
study of drugs in humans, in patients, in healthy volunteers
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Therapeutics (Pharmacotherapeutics)
- use of drugs to diagnose, prevent, or treat disease
- or to prevent pregnancy
- medical use of drugs
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Properties of an Ideal Drug (there is no such thing as an ideal drug)
- EFFECTIVENESS: elicits for which given, most important
- SAFETY: no harmful effects
- SELECTIVITY: only the intended response
- Reversible Axn: some drugs we want reversed, some we dont
- Predictability: unique patients- tailor to individual
- Ease of Admin: simple/convenient, enhance pt adherence, decr. med errors
- Freedom from Drug Interxns: safety
- Low Cost: can be a huge financial burden
- Chemical Stability: can lose effectiveness during storage or when dissovled
- Possess a Simple Generic Name: trade name much simpler, but generic is preferred
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Therapeutic Objective
provide maximum benefit with minimum harm
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5 Rights (plus 2)
Right Drug to the right Patient in the right Dose by the right Route at the right Time, with the right Documentation and before the Expiration Date
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Must Give Patient During Pharm. Pt. Educ.
- Drug name + therapeutic category
- Dosage size + schedule
- Route + technique of admin
- Expected therapeutic response + when should develop
- Nondrug measures to enhance effects
- Duration of treatment
- Method of storage
- Symptoms- major adverse fx, measure to minimize
- Major adverse drug-drug + drug-food intrxns
- Whom to contact
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Condraindication vs. Precaution
- Contraindications: pre-existing condition, avoid a particular drug under all but most desperate cirucumstances
- Precaution: pre-existing cond'n significantly increases risk of adverse rxn to a particular drug, but not life-threatening
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3 Types of Drug Names
- Chemical: long/complex, inappropriate for every day, description w/nomenclature of chemistry
- Generic: (nonproprietary) only one, preferable
- Trade: (proprietary) under which drugs are marketed, easy to recall/pronounce, must be FDA approved
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Pharmacokinetics vs. Pharamacodynamics
- Pharmacokinetics: how the body responds to the drug and gets it to the target site
- Pharmacodynamics: what the drug does to the body
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Pharmacokinetics
- study of drug movement throughout body
- Absorption: from site of admin into the blood
- Distribution: from blood into interstitial space of tissues, and from there, into cells
- Metabolism: (biotransformation) enzymatically mediated alteration of drug structure
- Excretion: movement of drugs/metabolites out of body
- Application to Therapeutics: max bens/min harm, intensity of response directly r/t concentration of drug at site of axn, balance achieved by selecting appropriate route/dose/schedule
- Three Ways to Cross Cell Membrane: (1) channels/pores, (2) transport systems, (3) direct penetration
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Factors Affecting Absorption
- Rate of Dissolution: rapid means faster onset
- Surface Area: larger = faster
- Blood Flow: great concentration gradient = more rapid absorption
- pH partitioning: pH plasma & pH admin site difference facilitates greater tendency to be ionized in plasma
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Determinants of Intensity of Response
- Administration: dosage, time, route; poor patient adherence/staff errors (=toxicity/treatment failure); errors detract from achievement of therapeutic objective
- Pharmacokinetics: “impact of body on drugs," how much of administered dose gets to the site of action
- 1. Drug absorption
- 2. Drug distribution
- 3. Drug metabolism
- 4. Drug excretion
- Pharacodynamics: “Impact of drugs on body," nature/intensity of response, drug-receptor interaction followed by sequence of events
- Individual Variation: drug interactions, physiologic variables (age, gender), pathologic variables (diminished organ fxn), genetic variables, must tailor drug therapy to individual
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Med Admin r/t Patient Care
- Pre-Admin Assessment: baseline, ID high risk, capacity for self care
- Dosage/Administration: dose depends in individual, indication, calculation
- Evaluation/Promote Therapeutic fx: eval, promote adherence, non-drug measures
- Minimize Adverse fx: ID high risk, forewarn of adverse fx, know your drugs
- Minimize Adverse Interactions: drug Hx, OTC intrxn, monitor for a/e, alert for unknown intrxn
- Making PRN Decisions: decide when/how/ehy
- Managing Toxicity: early signs, procedure for management
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Med Admin r/t Patient Education
- Must give patient drug info
- Dosage/Admin: name, dose size, technique, duration, storage
- Promote Ther. fx: pt knows nature & expected time course
- Minimize A/E: knowledge
- Minimize adverse intrxn
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Med Admin r/t Drug Therapy
- PreAdmin assessment: baseline, high risk, selfcare?, contraind/precautions
- Analysis/Nrsg Dx: judge appropriateness, ID potential health problems drug might cause, determine pt capacity for selfcare
- Planning: define goals, set priorities, ID interventions, est. criteria for eval
- Implementing: drug admin, pt educ, intrvn to promote ther. fx, intrvn to minimize adverse fx
- Eval: ther. response, a/e, adherence, satisfaction
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New Drug Development
- Randomized Controlled Trial (RCT): (to minimize personal bias)
- 1. Use of controls--standard drug vs. nondrug; placebo
- 2. Randomization--control group; experimental group
- 3. Blinding--single (subject blind); double (researcher + subjects blind)
- Stages of New Drug Development: preclinical; clinical (4 phases)
- Downfalls: Little info on women or children; failure to detect all adverse fx
- Exercising Discretion Regarding New Drugs:
- 1. Be neither the first to adopt to new, nor the last to abandon the old
- 2. Maximum benefit w/minimum harm
- 3. Balance potential benefits w/inherent risks
- 4. New drugs generally greater risks than old drugs
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(MEC) minimum effective concentration:
below which therapeutic benefit will not occur
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Toxic Concentration:
plasma level at which toxic levels begin
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Therapeutic Range:
- between MEC and Toxic Conc.
- objective is to maintain levels between
- wide range: safely with ease
- narrow range: difficult to be safe, more likely for complications
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Single Dose Time Course:
- levels rise in absorp then fall in metab/excr
- latency btwn admin and onset of fx
- duration determined by metab/excr
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Drug Half Life:
- time for amt of drug in body to decrease by 50%
- key point: percentage not amount is lost
- determines dosing interval
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Process of Plateau
- admin 2nd dose before 1st is eliminated
- levels increase w/each dose
- plateau achieved when amt of drug eliminated btwn doses equals dose admin'd (levels remain constant)
Time to Plateau: reached in approx. 4 half lifes
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Peak vs. Trough
- Peak Concentration: highest level (keep below toxic concentration)
- Trough Concentration: lowest level (keep above MEC)
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Loading Dose vs. Maintenance Dose
- Loading Dose: large intial dose (small doses to maintain plateau)
- Maintenance Dose: small doses maintain plateus after high drug level established w/loading dose
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Pharmacodynamics:
Dose-Response
(Maximum Efficacy, Relative Potency)
- relationship btwn size of admin dose and intensity of response produced
- graded relationship (↑dose = ↑response)
- can be adjusted to patient needs
- Maximum Efficacy: largest effect that a drug can produce, determined by height of D-R curve
- Relative Potency: amt of drug must be given to elicit effects, potent is to produce fx @low doses
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Pharmacodynamics:
Drug-Receptor
- specific chemical in body that drugs interact with to produce fx
- body has own receptors for endogenous compounds (hormones, NTs, etc)
- binding usually reversible
- drugs can mimic endogenous axn or block axn of endogenous compounds (cannot give new fxns/only alter rate)
- selectivity offers fewer side effects but does not guarantee safety (lock + key analogy)
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Simple Occupancy Theory:
- intensity of response is r/t #of receptors occupied by the drug
- maximal response occurs when all available receptors occupied
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Affinity:
- strength of intrxn/attraction btwn drug and receptor
- ↑affinity: strong attraction; very potent; bind at low concentrations
- ↓affinity: weak attraction; low potency; bind in high concentrations
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Intrinsic Activity:
- ability of drug to activate the receptor following binding
- ↑intrinsic activity: cause intense receptor activation; high maximal efficacy
- ↓intrinsic activity: cause slight activiation; low maximal efficacy
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Agonist vs. Antagonist
- Agonist: drug that mimic body’s own regulatory molecules, activate receptors, have affinity and intrinsic activity
- Antagonist: drug that blocks/prevent axn of endogenous regulators, affinity for receptor but no intrinsic activity (no receptor activation), most commonly for drug overdose
- Noncompetitive: binds irreversibly, decrease #cells receptors, reduce maximal response
- Competitive: binds reversibly, competes w/agonist for receptor binding, higher conc. wins
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Partial Agonist:
- mimic axns of regulatory molecules, but produce responses of intermediate intensity
- only moderate intrinsic activity
- maximal effect is lower than full agonist
- can act as both agonist/antagonist
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Therapeutic Index:
- measure of drug safety
- ratio of LD50 to ED50
- ↑index relatively safe
- ↓index rel. unsafe
- safety defined by highest dose requirex for thereapeutic fx substantially lower than lethal dose
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Drug-Drug Intrxn:
- Intensified fx: potentiative, ↑ther. fx, ↑adverse fx
- reduced fx: ↓ther. effects is detrimental, while ↓adv. fx is beneficial
- creation of unique response:response not characterized by one of single drugs alone
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Drug-Food Intrxn:
- ↑or↓absorption
- grapefruit juice effect
- food ↑risk toxicity
- affect drug action
- timing
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Drug-Supplement Intrxn:
dietary suppl can interact w/conventional drugs thru pharmacokinetic/dynamic mechanisms and increase toxicity or reduce beneficial response
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ADRs: Factors, Identifying, Minimizing
Factors: body weight/composition, age, pathophysiology, tolerance, placebo effect, variable absorption, genetics, gender, race, failure to take meds as prescribed
Identifying: shortly after first used, abate when disct’d, reappear when restart, illness itself or explained fx?
- Minimizing Adverse Rxn: Responsibility of everyone involved in drug production and use
- --Anticipation, early detection signs
- --Monitor fxn of target organ
- --Individualized therapy (potential risk vs. probable benefits)
- --Chronic disorders especially vulnerable
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Adverse Effect
noxious, unintended, undesired effect that occurs at normal doses; all body systems, variable intensity
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Side Effect
nearly unavoidable 2ndary drug effect produced at therapeutic doses
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Toxicity
adverse drug rxn caused by excessive dosing
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Allergic Reaction
prior sensitization of immune system, intensity largely independent of dosage
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Idiosyncratic Effect
uncommon drug response resulting from genetic predisposition
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Iatrogenic
disease produced by drugs; essentially identical to naturally occurring pathology
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Physical Dependence
develop w/longterm use, body has adapted to drug exposure, abstinence sydr will result if discont; patients should be warned
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Carcinogenic:
ability to cause cancers
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Teratogenic Effect
drug induced birth defect
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Medication Errors:
Types, Causes, Reporting, Reducing
Types: 13 major causes, cause harm directly or indirectly, fatal errors (wrong dose, overdose, wrong route)
- Cause: human factors, communication mistakes, name confusion (90% all errors)
- Reporting Errors: medication error report program (MER)
Reducing Errors: help/encourage pt to be active/informed members of HC team, give HC providers tools/info needed to prescribe/dispense/admin as safely as possible, computerized med orders, have senior pharmacist accompany on rounds, barcodes on everything, careful use of abbreviations
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3 Steps to Reduce Med Errors
- 1. Check/Double Check 6 Rights
- 2. Appropriate Knowledge Base
- 3. Clarify anything unsure about
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