Pharmacology II Dentistry 1

8/2/2019 Pharmacology II Dentistry 1

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PHARMACOLOGY II DENTISTRY

GENERAL & LOCAL ANESTHESIA

Dr Mohammed Shamssain


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Course Contents

General & local anesthetics

Sedative hypnotics & pharmacology of

alcoholism

Treatment of epilepsy & parkinsonism

Antipsychotics, anti depressant & anxiolytics

Pharmacology of pain Adrenal cortex hormones & steroidal anti-

inflammatory drugs


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Course Contents

Thyroid hormones & anti-thyroid drugs

Calcium metabolism

Gonadal hormones & their antagonists

Oral contraceptives

Pharmacology of diabetes mellitus

Antimicrobial agents

Antifungal & antiviral agents

Treatment of cancer & parasitic infestation


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Assessment

Quiz one: one hour; 20%; date: Monday 19th

March (1-2 pm)

Mid-term exam: one hour; 20%

Quiz two: one hour; 20%; date: Monday 14th

May (1-2 pm)

Final exam: two hours; 40%


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General

Noradrenaline: noradrenergic transmission is important in

control of mood (functional deficiency resulting

depression)

controlling wakefulness, and alertness Dopamine: is important in

motor control (parkinsonism is due to dopamine

deficiency)

has behavioural effects (excessive dopamine activity isimplicated in schizophrenia)

hormone release (prolactin, GH)

dopamine in chemoreceptor trigger zone causes nausea

& vomiting


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General

5-HT: physiological functions associated with 5-HTpathways include: feeding behaviour, behaviouralresponse, control of mood and emotion, control ofbody temperature and vomiting

Ach: has effects on arousal, on learning, and on shortterm memory. Dementia and parkinsonism areassociated with abnormalities in cholinergicpathways.

GABA (Gamma-AminoButyric Acid): is an inhibitoryNT in CNS

Glycine: an inhibitory NT , acts on GABA like receptorin spinal cord


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Anesthetics


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Ion Channels


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Synapse


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AnestheticSuppression ofPhysiologicalResponse to

Surgery


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Essential Components of Anesthesia

Analgesia- perception of pain eliminated

Hypnosis- unconsciousness Depression of spinal motor reflexes

Muscle relaxation

* These terms together emphasize the role ofimmobility and of insensibility!


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Stages of Anesthesia

In general anesthesia: the patient is

unconscious and has no awareness or othersensations.

The relationship between the amount ofgeneral anesthetic administered and the

depression of the brain's sensory usefullydivided into stages to describe the depth ofanesthesia.1,3,5


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Mechanism of Action

General Anesthetics CNS modifyingfunctions of ION CHANNELSmodifying theelectrical activity of neurons at a molecular level

This may occur by anesthetic molecules binding directly to ion channels or

by their disrupting the functions of molecules thatmaintain ion channels.

a general anesthetic is a drug that has the abilityto bring about a reversible loss of consciousness by act on CNS via shutting off the brain from external

stimuli


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Anesthetics divide into 2 classes:

InhalationAnesthetics

Gasses or Vapors

Usually Halogenated

IntravenousAnesthetics

Injections

Anesthetics or inductionagents


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What are General Anesthetics?

A drug that brings about a reversible loss of

consciousness. Administered by an anesthesiologist in order

to induce or maintain general anesthesia tofacilitate surgery.


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Pathway for General Anesthetics


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Pathway for General Anesthetics

Partial Pressure in brain quickly equilibrates

with partial pressure in arterial blood whichhas equilibrated with partial pressureperfused alveoli.

DEPTH of anesthesia induced by an inhaled

anesthetic depends primarily on thePARTIAL PRESSURE!!! Of the anestheticsin the brain


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Pathway of General Anesthetics

Rate of induction and recovery from

anesthesia depends on the rate of change ofpartial pressure in the brain.

These drugs are small lipid-solublemolecules that cross the alveolar membrane

easily. Move into and out of the blood basedon the partial pressure gradient.


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Variables that Control Partial Pressure

in Brain

Direct Physician's Control Solubility of agent

Concentration of agent in inspired by air

Magnitude of alveolar ventilation

Indirect Physicians Control Pulmonary blood flow-function of CO

Arteriovenous concentration gradient


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Rate of Entry into the Brain: Influence

of Blood and Lipid Solubility


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Rate of Entry into the Brain

LOW solubility in blood= fast induction and

recovery HIGH solubility in blood= slower induction

and recovery.


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General Anesthetics


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General Anesthetics


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General Actions of Inhaled Anesthetics

Respiration

Depressed respiration and response to CO2 Kidney

Depression of renal blood flow and urine output

Muscle

High enough concentrations will relax skeletalmuscle


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Cont

Cardiovascular System

Generalized reduction in arterial pressure andperipheral vascular resistance. Isofluranemaintains CO and coronary function better thanother agents

Central Nervous System Increased cerebral blood flow and decreased

cerebral metabolism


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Inhaled Anesthetics


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Inhaled Anesthetics

Halothane

Enflurane

Isoflurane

Desflurane

Halogenatedcompounds:

ContainFluorineand/orbromideSimple, small

molecules


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Injectable Anesthetics


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Intravenous Anesthetics

Used in combinationwith Inhaled

anesthetics to: Supplement general

anesthesia

Maintain generalanesthesia

Provide sedation

Control blood pressure

Protect the brain


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Adjunct Agents


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Anticholinergic Drugs

Block the effects of Ach and other cholinergic

drugs at cholinergic receptors of effector cells

Two major types

Antinicotinics include ganglion blockers and

neuromuscular blockers

Anti muscarinics include tertiary amines (e.g:

atropine , scopolamine, etc)


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Mechanism of Action of Anesthesia


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MAC:Minimum Alveolar Conc

MAC is a concept used to compare the

strengths, or potency, of anaesthetic vapours

Defined as the concentration of the vapour in

the lungs that is needed to prevent movement

(motor response) in 50% of subjects in response

to surgical (pain) stimulus.

A lower MAC value represents a more potent

volatile anesthetic.


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Overton Meyer Theory

O-M Theory: The MAC of a volatile substance isinversely proportional to its lipid solubility (oil:gascoefficient)

MAC is inversely related to potency i.e. high macequals low potency.

The hypothesis correlates lipid solubility of ananaesthetic agent with potency (1/MAC)

Onset of anaesthesia occurs when sufficientmolecules of the anaesthetic agent havedissolved in the cell's lipid membranes, resultingin anaesthesia


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Indications


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Side Effects


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Local Anesthetics


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Types of Local Anesthetics


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Parenteral Anesthetic Agents


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Drug Effects


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Indications


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Side Effects


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Neuromuscular Blocking Agents


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NMBAs


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NMBAs:Depolarizing Agents


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NMBAs:Non-Depolarizing Agents


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NMBAs


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NMBAs:Indications


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NMBAs: Side Effects


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NMBAs: Overdose


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Depression of respiratory drive

Decreased CO2 drive (medullary chemoreceptors),

Takes MORE CO2 to stimulate respiration

Depressed cardiovascular drive

Gaseous space enlargement by NO

Fluoride-ion toxicity from methoxyflurane

Metabolized in liver = release of Fluoride ions

Decreased renal function allows fluoride toaccumulate = nephrotoxicity

Toxicity and Side Effects


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Moderate Sedation


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Dentistry Implications


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Pharmacology II Dentistry 1

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