Chapter 2Chapter 2

Pharmacokinetics and Pharmacokinetics and PharmacodynamicsPharmacodynamics

PharmacotherapeuticsPharmacotherapeutics

The study of how drugs are used to treat, The study of how drugs are used to treat, prevent, and diagnose disease and prevent, and diagnose disease and illnessillness Pharmacokinetics – how the body Pharmacokinetics – how the body

assimilates, incorporates, and eliminates a assimilates, incorporates, and eliminates a drugdrug

Pharmacodynamics – how a drug affects the Pharmacodynamics – how a drug affects the bodybody

You will be able to You will be able to explain to an athlete…explain to an athlete…

Why it is important to take medications Why it is important to take medications as prescribed by a physicianas prescribed by a physician

How drugs workHow drugs work Why drugs workWhy drugs work How long a drug remains activeHow long a drug remains active What the potential drug adverse effects What the potential drug adverse effects

areare Other general questions they askOther general questions they ask

What is a Drug?What is a Drug?

A chemical that interacts with and affects A chemical that interacts with and affects living organisms to produce a biological living organisms to produce a biological responseresponse

A drug alters physiological functions by A drug alters physiological functions by replacing, interrupting, or potentiating replacing, interrupting, or potentiating existing cellular functionsexisting cellular functions

Primary or secondary effectsPrimary or secondary effects

PharmacodynamicsPharmacodynamics

Receptor Sites – a component of a cell to Receptor Sites – a component of a cell to which a drug binds to produce an effectwhich a drug binds to produce an effect

Most drugs act at specific locations in Most drugs act at specific locations in tissues or organstissues or organs

““lock and key” analogy (pgs 18-19)lock and key” analogy (pgs 18-19) Affinity – the force that makes 2 agents Affinity – the force that makes 2 agents

bind or unitebind or unite Efficacy – the capacity to elicit a Efficacy – the capacity to elicit a

responseresponse

Dose ResponseDose Response Threshold – lowest dose capable of Threshold – lowest dose capable of

producing a perceivable responseproducing a perceivable response Potency – amount of a drug necessary to Potency – amount of a drug necessary to

produce a desired effectproduce a desired effect Figure 2-2 Pg 19Figure 2-2 Pg 19

Time ResponseTime Response Determining the time response of a dose:Determining the time response of a dose:

LatencyLatency – “onset of action”, time required to – “onset of action”, time required to produce an observable effectproduce an observable effect

Maximal EffectMaximal Effect – time required to reach peak – time required to reach peak efficacyefficacy

Duration of ActionDuration of Action – time period over which – time period over which a drug produces a response after a single a drug produces a response after a single dosedose

Time ResponseTime Response Influenced by:Influenced by:

Route of administrationRoute of administration Solubility of the drugSolubility of the drug How fast the drug is distributed to action siteHow fast the drug is distributed to action site Time it takes to be inactivated and excreted Time it takes to be inactivated and excreted

from the bodyfrom the body

Therapeutic Index – the range in which Therapeutic Index – the range in which desired effects are produceddesired effects are produced

Used to determine the safety parameters Used to determine the safety parameters of dosesof doses

Half-Life – determined by the time required to Half-Life – determined by the time required to reduce by one-half the amount of the drug reduce by one-half the amount of the drug present in the bodypresent in the body

Drugs have different & distinct half-livesDrugs have different & distinct half-lives Comparison for drug elimination ratesComparison for drug elimination rates Determines frequency with which multiple Determines frequency with which multiple

doses of a drug can be safely administereddoses of a drug can be safely administered Half-life does not change with the drug doseHalf-life does not change with the drug dose

PharmacokineticsPharmacokinetics

Absorption – speed, rate, and extent of Absorption – speed, rate, and extent of absorption is dependant on its’ physical absorption is dependant on its’ physical and chemical propertiesand chemical properties Solubility of the drugSolubility of the drug Surface area of intended site of actionSurface area of intended site of action Specific route of administrationSpecific route of administration

EnteralEnteral

Oral ingestion - safest, most common, Oral ingestion - safest, most common, convenient, economical route of convenient, economical route of administrationadministration

Taken by mouth = onset of action within 1 Taken by mouth = onset of action within 1 hourhour

Oral mucosa – sublingual or buccal routesOral mucosa – sublingual or buccal routes Vast capillary blood supply = dissolve Vast capillary blood supply = dissolve

rapidlyrapidly

EnteralEnteral

Preliminary passage or “first-pass Preliminary passage or “first-pass metabolism” Figure 2-7 pg 24metabolism” Figure 2-7 pg 24

SolutionsSolutions Liquid form, syrups, elixirsLiquid form, syrups, elixirs

Capsules and tabletsCapsules and tablets Sustained-releaseSustained-release

ParenteralParenteral

Non-oral route of administrationNon-oral route of administration Drug delivered directly to target siteDrug delivered directly to target site Not subjected to first-pass metabolism Not subjected to first-pass metabolism Routes includeRoutes include

SubcutaneousSubcutaneous IntramuscularIntramuscular IntravenousIntravenous IntrathecalIntrathecal Intra-articularIntra-articular

InhalationInhalation

Form of gases or fine mistsForm of gases or fine mists Lungs: large surface area and rich blood Lungs: large surface area and rich blood

supply = effective means of absorbing supply = effective means of absorbing and transporting meds into blood supply and transporting meds into blood supply rapidlyrapidly

Special devices propel meds onto Special devices propel meds onto alveolar and bronchial tissuesalveolar and bronchial tissues

TopicalTopical

Applied to skin or mucous membranesApplied to skin or mucous membranes Difficult to reach systemic circulationDifficult to reach systemic circulation Used to treat skin problemsUsed to treat skin problems RoutesRoutes

OintmentsOintments CreamsCreams Transdermal patchesTransdermal patches

PharmacokineticsPharmacokinetics

Distribution – to act on a specific receptor Distribution – to act on a specific receptor site, the drug must pass through the site, the drug must pass through the different biological layers and then be different biological layers and then be transported to the site via the transported to the site via the bloodstreambloodstream

Cell membrane reviewCell membrane review

Modes of transportation across cell Modes of transportation across cell membranemembrane FiltrationFiltration DiffusionDiffusion Active transportActive transport

PharmacokineticsPharmacokinetics

Metabolism – process of ridding the body Metabolism – process of ridding the body of foreign substance (biotransformation)of foreign substance (biotransformation)

Breakdown of original drug compound Breakdown of original drug compound into metabolites, which are eliminatedinto metabolites, which are eliminated

Rate of metabolismRate of metabolism Liver is primary organ, specialized Liver is primary organ, specialized

enzymes that metabolize drugs or foreign enzymes that metabolize drugs or foreign compoundscompounds

PharmacokineticsPharmacokinetics

Excretion Excretion Routes of drug eliminationRoutes of drug elimination

Urine, bile, fecesUrine, bile, feces Lungs, salivary, sweat, mammary glandsLungs, salivary, sweat, mammary glands

Kidney is major organKidney is major organ Patient HealthPatient Health

Factors Affecting Drug Factors Affecting Drug ResponseResponse

AgeAge Infants & older adultsInfants & older adults

Weight & GenderWeight & Gender Men vs. womenMen vs. women Dosing based on weightDosing based on weight

Time of administrationTime of administration With food vs. before mealsWith food vs. before meals

Barriers to Drug Barriers to Drug DistributionDistribution

Blood-brain barrierBlood-brain barrier Placental barrierPlacental barrier Barriers inhibit certain chemicals in the Barriers inhibit certain chemicals in the

bloodstream that may be dangerous or bloodstream that may be dangerous or toxic to the individual or fetustoxic to the individual or fetus

Drug SafetyDrug Safety

Five Rights of Drug AdministrationFive Rights of Drug Administration Right drugRight drug Right patientRight patient Right doseRight dose Right routeRight route Right timeRight time

Other guidelines:Other guidelines: Drug prescribed = Drug dispensedDrug prescribed = Drug dispensed Read Directions carefullyRead Directions carefully Missed dosingMissed dosing Proper storageProper storage Safe storageSafe storage Know medical historyKnow medical history PotentiationPotentiation