B5

B5-Pharmacology Faller, Paul Jerome; Feliciano, Daniel Dennison; Flores, Ciara Joyce; Flores, Kathleen Joy; Fortuno, Julius Henry; Fuentes, Malou; Gabaton, Niña; Gallardo, Sheila; Ganal, Jonathan; Garcia, Ma. Irka; Gaspar, Irish Vanessa; Gatchalian, Cheryll; Generillo, Arvin; Glorioso, Anna Ma. Jolina; Go, Ferranti; Go Ricci Gayle 1

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Objectives General Objective: To determine the drug

interaction that exists between morphine and nalbuphine

Specific Objective: To compare the

duration of the mouse tail erection with morphine alone and with morphine followed by nalbuphine

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Materials Animals: 8 mice of the same sex and approximate

weight (32 mice used for the whole 2nd year batch) Instruments: Animal weighing scale Tuberculin syringe Animal cage Asbestos gloves 5

Materials Drugs: Morphine Prep

: 10 mg/mL (1%) Inject: 0.5 mL/20 g mouse Nalbuphine Prep

: 10 mg/mL (1%) Inject: 0.1 mL/20 g mouse 7

Methodology 1. Assign the mice randomly and equally into 2

2. 3. 4.

5.

groups: Morphine and Morphine + Nalbuphine. Inject Morphine intraperitoneally to each mouse based on the dose computations. Observe for erection of the tail (90˚ angle). Upon erection of the tail, inject Nalbuphine intraperitoneally to all the mice of the Morphine + Nalbuphine group based on dose computations. Compare the duration of tail erection

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Inject the mice intraperitonea lly

Rationale for Procedures Mice of the same sex with similar weights were assigned into two (2) groups.  Rationale:  To ensure precision and accuracy of obtained data  For easier calculation and preparation of appropriate drug dosage  To eliminate the effects of body weight and sex on the pharmacokinetic and pharmacodynamic parameters of each drug. 10

Rationale for Procedures 1) Morphine Group: Tx: Morphine

Morphine-Nalbuphine Group: Tx:

Morphine +Nalbuphine

 Rationale:  Two groups were used to facilitate comparison of the effect of morphine alone & morphine-nalbuphine drug interaction.

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Rationale for Procedures 1) 1% Morphine solution (0.5 mL / 20 g mouse)

was injected intraperitoneally to all of the mice.  Rationale:  Intraperitoneal injection for wider diffusion of the drug

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Rationale for Procedures 1) When the tail was observed as erect, the

mice in the Morphine-Nalbuphine group were injected with 1 % Nalbuphine (0.1 mL / 20 g mouse).

 Rationale:  Morphine-induced tail erection (MITE) or Straub tail is a marker indicating that morphine has taken its effect.  Tail erection was recorded when the tail rose to an angle of 90˚relative to the plane of the mouse body. 

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Morphine Mouse

weight (g)

 

duration of tail erection (s)

Morphine with Nalbuphine Mouse

weight (g)

duration of tail erection (s)

A1

≈ 20.00

1849.00

A5

≈ 20.00

1690.00

A2

≈ 20.00

1598.00

A6

≈ 20.00

382.00

A3

≈ 20.00

2010.00

A7

≈ 20.00

316.00

A4

≈ 20.00

1717.00

A8

≈ 20.00

289.00

B1

23.50

3475.00

B5

24.00

3371.00

B2

23.00

1873.00

B6

22.50

1630.00

B3

21.00

2268.00

B7

21.50

1931.00

B4

20.50

2074.00

B8

21.00

1683.00

C1

23.30

564.00

C5

23.30

343.00

C2

20.09

1499.00

C6

20.90

819.00

C3

20.00

1478.00

C7

20.03

786.00

C4

19.80

1653.00

C8

19.50

1398.00

D1

29.20

845.00

D5

29.20

353.00

D2

28.10

1535.00

D6

28.80

900.00

D3

28.10

450.00

D7

27.20

1176.00

D4

26.50

981.00

D8

24.20

1440.00 15

Duration of Tail Erection in Morphine and Morphine-Nalbuphine Groups 4000.00

Morphine

Duration (in seconds)

3500.00

Morphine and Nalbuphine

3000.00 2500.00 2000.00 1500.00 1000.00 500.00 0.00 A1/A5

A2/A6

A3/A7

A4/A8

B1/B5

B2/B6

B3/B7

B4/B8

C1/C5

Mouse

C2/C6

C3/C7

C4/C8

D1/D5

D2/D6

D3/D7

D4/D8

Results Descriptive Statistics Mean Standard Deviation

Morphine

Morphine with  Nalbuphine

Overall

1616.81

1156.69

1386.75

724.86

821.06

796.92

T-test for Independent groups t critical

2.042 two-tailed 1.697 one-tailed

t value

1.680

  α level

0.050

p value

0.103

The t and p value were both not significant. 17

Results In general, there was a decrease in the duration

of tail erection in the Morphine-Nalbuphine group. Only D3-D7 and D4-D8 mice pairs exhibited a different result. There was no significant difference in the tail erection duration between the two groups.

Results Sources of error: Technique of drug administration Different indications for tail erection and drug administration among experimenters Accuracy of time measurement and dose computation Level of expertise

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Agonist bind to and activate the receptor which

directly or indirectly brings about the effect 1. Full Agonist- is able to elicit a maximal response following receptor occupation and activation 2. Partial Agonist – produces a lower response, at full receptor occupancy, than do full agonists 21

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Antagonism the process of inhibiting or preventing an

agonist-induced receptor response Based on the kinetics of interaction of the

antagonist with the receptor, antagonism is classified as competitive and non-competitive.

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Antagonism 1.

Competitive Antagonist - competes with agonists for receptors - when the receptor is occupied by the antagonists, agonist cannot bind to the receptor

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Noncompetitive Antagonist - binds to the site other than the agonist binding domain - induces a conformational change in the receptor such that the agonist no longer recognizes the agonist binding domain 24

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Opioid Analgesics Act on the opioid receptors in

the nervous system Used to relieve moderate to severe pain Has antitussive, constipating actions Can cause respiratory depression

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Opioid Receptors  three opioid receptors: μ, κ, δ

Mu (µ)

o Analgesia, drowsy, euphoria and respiratory depression o Subdivided into µ1 and µ2: µ1 responsible for analgesia o Most clinically useful drugs act: Morphine

Kappa (k)

o analgesia, sedation, limited respiratory depression and

some dysphoria. o high affinity as agonists of k receptors o act as µ receptor antagonists o Example: Nalbuphine

Delta (d)

o endogenous opioids particularly the enkephalins o but no drugs exist that act exclusively through this

receptor.

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Classification of Opioid Analgesics 1. Full Agonist – ex. Morphine 2. Weak Agonist – ex. Codeine 3. Mixed agonist-antagonist – ex. Nalbuphine,

Pentazocine, Butorphanol 4. Pure Antagonist - Naloxone

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Morphine • highly potent opiate analgesic • derived from the opium poppy • Classification: phenanthrene • full agonist • Highly addictive and tolerance occur rapidly 30

Mechanism of Action  Produce analgesia: binding to specific G protein-coupled

receptors in the brain and spinal cord regions involved in pain transmission and modulation  Acts specifically on: μ receptors  Two established G protein-coupled actions: o close Ca2+ channels: reduce transmitter release o open K+ channels: hyperpolarize and inhibit postsynaptic neurons  Opioid agonists o inhibit the release of excitatory transmitters from the primary

afferents o directly inhibit the dorsal horn in pain transmission

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Pharmacokinetics  Absorption: SC, IM, and oral routes  Distribution: o High: brain, lungs, liver, kidneys and spleen o Low: skeletal muscle o may accumulate in fatty tissue

 Metabolism: o primarily conjugated: morphine-3-glucuronide o 10% is metabolized to morphine-6-glucuronide o these metabolites do not readily pass the BBB

 Excretion o primarily in the urine o small portion in the enterohepatic circulation (bile)

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Clinical Use  Analgesia  Acute pulmonary edema o mechanism: reduces anxiety (perception of shortness of

breath), reduced cardiac preload (reduced venous tone), reduced afterload (decreased peripheral resistance)  Cough  Diarrhea o controlling diarrhea but not in treating infection  Shivering  Anesthesia o premedicant drugs prior to surgery o also used as regional analgesics (epidural administration)

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Contraindications Tolerance Withdrawal syndrome Use in patients o with head injuries: increase ICP o during pregnancy: fetus may become dependent in utero o with impaired pulmonary function: acute respiratory

failure o with impaired hepatic or renal function o with endocrine diseases: prolonged and exaggerated responses

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Nalbuphine synthetic narcotic

agonist-antagonist analgesic of the phenanthrene series. strong kappa agonist and a mu receptor antagonist 35

Nalbuphine CNS Nervousness, depression, restlessness, crying,

euphoria, floating, hostility, unusual dreams, confusion, faintness, hallucinations, dysphoria, feeling of heaviness, numbness, tingling, unreality. Psychotomimetic effects: unreality, depersonalization, delusions, dysphoria and hallucinations

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Nalbuphine CARDIOVASCULAR Hypertension, hypotension, bradycardia,

tachycardia, pulmonary edema.

• GASTROINTESTINAL -- Cramps, dyspepsia, bitter taste • RESPIRATION -- Depression, dyspnea, asthma • DERMATOLOGICAL 

Itching, burning, urticaria 37

Morphine + Nalbuphine MORPHINE Full agonist NALBUPHINE primarily a kappa agonist / mu antagonist analgesic when administered following or concurrent with mu

agonist opioid analgesics (e.g., morphine), nalbuphine may partially reverse or block opioidinduced respiratory depression from the mu agonist analgesic

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Pharmacology B5