Experiment 2: Factors Affecting Drug Experiment 2: Factors Affecting Drug ActionAction

A. INFLUENCE OF ROUTE OF ADMINISTRATION

2A – MedSubsection A2

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ObjectivesObjectivesGeneral Objectives

◦To determine how the route of administration influences the action of ketamine hydrochloride

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ObjectivesObjectivesSpecific Objectives

◦To determine the latency (sec) and duration of effect (sec) of ketamine hydrochloride when administered intravenously and intramuscularly

◦ To statistically determine if there is a significant difference between the (a) latencies and (b) durations of effect of ketamine hydrochloride in the IV and IM group

◦To determine the effect of route of administration in the absorption and efficacy of ketamine hydrochloride

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Definition of terms:Latency/Time to Peak Effect - Time between initial

administration and onset of the maximum expected effect.

Duration of Effect - Length of time peak effect can be expected to last after a single administration of an anesthetic dose.

Righting reflex - A reflex resulting in the body or a body segment tending to regain its former body position when it is displaced.

ESSENTIALS FOR ANIMAL RESEARCH:A PRIMER FOR RESEARCH PERSONNEL

Second EditionMarilyn J. Brown, D.V.M., M.S

http://dcminfo.wustl.edu/education/primer_chap4.htm

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METHODOLOGYMETHODOLOGY

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Ketamine hydrochlorideKetamine hydrochloride

Preparation : 50mg/mL

Dosage : 5mg/Kg

2-(O-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride

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Ketamine hydrochlorideKetamine hydrochloridewater-solublewhite crystallinepKa=7.5commercially available

pharmaceutical form is in aqueous solution

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Ketamine

2-(2-chlorophenyl)-2-(methylamino)-cyclohexanone

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Ketamineanesthetic drugblocks the N-methyl-D-aspartate (NMDA)

glutamate receptor = non-competitive NMDA-receptor antagonist

inhibits activation of NMDA receptor by glutamate

reduces presynaptic release of glutamatepotentiates effects of GABA

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Experimental Animal: Experimental Animal: RabbitRabbit

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SECTION A

SECTION D

SECTION B

SECTION C10

WeighingWeighing

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DosageDosage

Dosage of drug=(weight of rabbit)(5mg/kg)(1mL/50mg)

e.g.:(1.5kg)(5mg/kg)(1mL/50mg) = 0.15mL

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Intramuscularly (IM)Intramuscularly (IM)

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Intravenously (IV)Intravenously (IV)

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Time of injection

Time the righting reflex was lost

Time the righting reflex was regained

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Righting reflex“static reflex”bring the body into normal position in

spaceresist forces acting to displace the

body out of normal positionturns a falling animal's body in space

so that its paws or feet are pointed at the ground; hence, returns the animal to sternal recumbency after being placed on its back or side

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Rabbit with no righting reflex

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RESULTS and DISCUSSIONRESULTS and DISCUSSION

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Tabulation of results- Route of AdministrationTabulation of results- Route of Administration

SECTION Latency Duration of Effect

Intramuscular(seconds)

Intravenous(seconds)

Intramuscular(seconds)

Intramuscular(seconds)

A 1 335 11 472 876

2 129 10 322 1112

B 3 170 31 172 371

4 217 30 147 361

C 5 76 7 852 995

6 150 9 517 1357

D 7 232 5 906 880

8 193 9 898 662

Mean 187.75 14 535.75 826.75

SD 72.632207 9.68245837 296.19873 325.552511

Variance 5275.4375 93.75 87733.6875 105984.438

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Actual ResultsActual Results

L atenc y

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200

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400

0 1 2 3 4 5 6 7 8 9

ra bbit no.

tim

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intramus cular

intravenous

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Actual ResultsActual Results

0200400600800

1000120014001600

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tim

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rabbit no.

Duration

intramuscular

intravenous

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Actual ResultsActual ResultsLatency (Mean)

◦Intravenous = 14 seconds◦Intramuscular = 187.75 seconds

Duration (Mean)◦Intravenous = 826.75 seconds◦Intramuscular = 535.75 seconds

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Hypothesis

Ho: there is no significant difference in the latency/duration between intramuscular and intravenous administration

H1: there is significant difference in the latency/duration between intramuscular and intravenous administration

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Formula for calculating independent t statisticsTest statistic Its value is used to decide whether or not the null hypothesis should

be rejected in our hypothesis test

= difference between population means

= Pooled standard deviation

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Latency

Count mean variance Standard deviation

Intramuscular 8 187.75 5275.44 72.63

Intravenous 8 14 93.75 9.68

= √ 5275.44(8-1) + 93.75(8-1) √ 8+8-2 = 51.81

t = (187.75 – 14) – 0

51.81 √1/8+1/8

= 7.00

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Critical regionSet of values of the test statistic for

which the null hypothesis is rejected in a hypothesis test

df = n1+n2 -2 df = 14Critical region = 1.7613

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t = 7.00Critical region = 1.76

7.001.76

Fail to reject Ho

Reject Ho

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Duration

Count mean variance Standard deviation

Intramuscular 8 535.75 87733.69 296.20

Intravenous 8 826.75 105984.44 325.55

Sp= √ (8-1) 87733.69 + (8-1) 105984.44 8+8-2 Sp =311.22

t = (535.75 – 826.75) – 0

311.22√1/8+1/8

= -2.64

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Duration

1.76

Fail to reject Ho

Reject Ho

t = -2.64

Critical region : 1.7613

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Actual Results: StatisticsActual Results: StatisticsStudent t test

t test for two independent variablesSignificance level = 0.05

LatencyIntramuscular vs IntravenousP value 0.00017991< 0.05There is significant difference

DurationIntramuscular vs IntravenousP value 0.05115812 > 0.05There is no significant difference

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Expected resultsExpected resultsIV route has faster onset of action than

IM route

Duration of action is greater in IM than the IV route

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Intravenous Drug AdministrationIntravenous Drug Administration

Intravenous (IV) [drug administered directly into the bloodstream]

Avoids first pass metabolismRapid and complete absorption

[100% Bioavailability]Fastest rate of drug delivery and

onset of action

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Intravenous Drug AdministrationIntravenous Drug Administration

Maximal degree of control over drug circulating levels

No way to stop response to drug (no recall)

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Intramuscular Drug AdministrationIntramuscular Drug Administration

Intramuscular (IM) - Rapid absorption and onset of action• Uptake of drug dependent on blood flow at the

injection site and solubility of the drug.

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IV versus IM Drug AdministrationIV versus IM Drug Administration

Onset of action is indeed faster in the IV route.

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DURATION OF ACTION

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Sources of ErrorHuman Error:

◦The administration of drug was done by different experimenter

◦The time of observation of latency and duration was done by different people

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CONCLUSIONCONCLUSION

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IV route has faster onset of action than IM route

The onset of action is dependent on the route of administration

Onset of action

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Duration of actionDuration of action in the intramuscular

route is dependent on the solubility of the drug

The IM route has a longer duration of action than the IV route

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ReferencesReferences

Howland, Richard and Mycek, Mary. Lippincott's Illustrated Reviews. Lippincott Williams and Wilkins, 2006.

Katzung, Betram G. Basic and Clinical Pharmacology, 10th ed. The McGraw-Hill Companies, Inc, 2007.

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THANK YOU!THANK YOU!

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ToleranceTolerance

Repeated use of ketamineusers can develop a tolerance and/or dependence to the

drug.Rises quickly with regular use and lasts about three days

Can be very high and develop rapidly to the point where after a period of time users will no longer experience the dissociative effects they first began using

Chronic use can cause development of a very high, almost permanent, tolerance to the drug.

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Ketamine AbsorptionKetamine Absorption

Ketamine is rapidly absorbed when administered through the intramuscular (Tmax 5-15 min), nasal (Tmax 20 min) or oral route (as a solution) (Tmax 30 min).

Bioavailability is low when ketamine is given orally (17%) or rectally (25%). Extensive first pass metabolism in liver and intestine is largely responsible for this effect. Bioavailability after nasal administration is approximately 50% (Malinovsky et al., 1996)

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Ketamine DistributionKetamine Distribution• Ketamine has a high lipid solubility and low

plasma protein binding (12%), which facilitates rapid transfer across the blood-brain barrier.

Initially it is distributed to highly perfused tissues, including the brain, to achieve levels 4-5 times those in plasma (distribution half-life after i.v. 24 sec.).

CNS effects subside, following redistribution to less well-perfused tissues (re-distribution half-life 2.7 min.).

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Ketamine MetabolismKetamine MetabolismBiotransformation primarily takes place in the liver.

The most important pathway is N-demethylation to norketamine. When administered orally or rectally, initial plasma norketamine concentrations are higher than those of ketamine are, but the plasma area under the curve (AUC) for norketamine is similar for all routes of administration. Norketamine has one-third the anaesthetic potency of ketamine and has analgesic properties. Norketamine may be metabolised through multiple pathways, but the majority is hydroxylated and subsequently conjugated.

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Ketamine EliminationKetamine EliminationThe predominant route of elimination

is by liver metabolism. The high extraction rate (0.9) makes ketamine clearance susceptible to factors affecting blood flow. The conjugated hydroxy metabolites are mainly excreted renally. Terminal elimination half-lifes are ranging from 100-200 minutes.

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