Dr. Yieldez Bassiouni

How pain is transmitted?

The injury will cause release of various pain chemical mediators like prostaglandin, histamine, serotonin, bradykinin and substance P.

These mediators will stimulate the pain receptors in the skin.

Pain signals are generated and transferred via the sensory nerve to the spinal cord to the thalamus -then the massage come out of the spinal cord and travel via motor nerve to the arm muscle, causing the arm to withdraw quickly -no sensation under the skin (subcutaneous or in muscles)

Analgesia means no pain

Analgesics are agents which relieve the pain without disturbing consciousness

Analgesics are divided in to two main classes:

1) Opioid analgesics2) Non-opioid analgesics

(analgesics-antipyretics)

Opioid Non-Opioid analgesics (analgesics-antipyretics)

Are the most powerful analgesics that can relieve any type of pain

Act mainly at the level of the cortex. CNS

Can produce addiction

Example: Morphine and codeine

Are mild analgesics that treat mild types of pain as headache…..

Act at the level of the thalamus & hypothalamus

No addiction

Example: NSAIDs e.g. salicylates, and paracetamol

Opioid AnalgesicsOpioids are drugs acting at opioid receptors, morphine is the prototype of opioid agonists.

Opioid analgesics are potent drugs which selectively depress the CNS and relieve pain.

They are mainly obtained from unripe capsules of Opium poppy plant.

OPIOIDS OPIATES derived directly from opium poppy natural or synthetic with morphin – like actionMay be narcotic or non narcotic

The important alkaloid isolated from opium is morphine. Other alkaloids isolated from opium are codeine and papaverine.smooth muschle relaxant

Examples of Opioid DrugsNatural

morphine codeine

semisynthetic heroim( methymorphinsynthetic

Pethidine 1/5 morphin activity+ less addiction or meperidine

methadone for Rx of addiction fentanyl

Opioid Receptors Opioid Receptors •Several types of opioid Several types of opioid

receptors have been receptors have been identified at various sites in identified at various sites in the nervous system and other the nervous system and other tissues.tissues.• These are Mu (These are Mu (μμ), Kappa ), Kappa

((κκ) , sigma and Delta (∂) ) , sigma and Delta (∂) receptors receptors ..

Action

Therapeutic uses

Morphin addict charactiristic pin point pupil (miosis)

Adverse effects

Nausea and vomiting

May lead to death

Why do we ?

It is a defensive

mechanism to removes

excessive secretions

Removes potentially

harmful foreign

substances (beneficial)In some situations, coughing can be

harmful, such as after hernia repair

surgery

Cough receptors

bronchi, diaphragm, external auditory canal, larynx, nose, paranasal sinuses , pericardium, pharynx, pleura, stomach, trachea and tympanic membrane.

Two Basic Types of Cough

Cough interferes with sleep and work

Give expectorant Give antitussive

Antitussives = cough suppressant

Drugs used to stop or reduce

coughing

Opioid and non-opioid

Used only for nonproductive coughNB: when pnt has productive cough, give expectorant Not antihistamine because it will dry the sputum and make it thick harder to expel (vicid)

MoA of Antitussives

1) Depression of medullary center 2) Increases threshold of the cough center3) Interruption of impulses peripherally in

the respiratory tract4) Inhibition of conduction along the motor

pathwaysWork on stretch receptors on lungs numb them inactiveSoothing effect (ex: lozanges)

1- Centrally acting Antitussives Narcotic antitussives Codeine Pholcodine Hydrocodone Non narcotic antitussives Dextromethorphan Noscapine

2- Peripheral Antitussives Inhibition of the cough receptors of

Pharynx: Larynx1Demulcents

LinctusLozengesLiquorice

2InhalationBenzoinMenthol

3Local anaesthetics on pulmonary stretch receptors of alveoli: BenzonatateLignocaine (only in special circumstances)

Narcotic AntitussivesCodeine An opium alkaloid similar to morphine less potent than morphine as analgesic and

respiratory depressant. 60% effective orally. A standard antitussive A small fraction of administered codeine is

metabolized to morphine which is responsible for analgesic effects of codeine. Euphoric effect used for sever cough of bronchogenic carcinoma

Less addictive Used limited due to SE.

MOA of Codeine: Directly suppresses cough centre in

Medulla. Suppresses cough for about 6 hrs.

Adverse effects of Codeine: In therapeutic doses minimum side effects

Sedations, nausea, constipation At higher doses respiratory depression and

drowsiness can occur. Contraindicated in asthmatic patients.

Can cause tolerance and dependance.

Pholcodeine

Pholcodeine has similar efficacy as codeine with longer duration of action of 12hrsIt has no analgesic or addiction property no euphoria

Non Narcotic Antitussives

Dextromethorphan Hydrobromide A synthetic compound. Strong and partial µ agonist. As effective antitussive as codeine. MOA:1. Controls cough spasm by depressing cough

center in medulla2. Increase the threshold for coughing

Advantages of Dextromethorphan

No effect on ciliary activity No CNS depression No addiction potential No constipation

Contraindicated in children below 6 yrs of age and also in patients taking Monoamine oxidase inhibitors.

NoscapineAn opium alkaloid No narcotic, analgesic or dependance

inducing properties. Equally effective antitussive as codeineUseful for spasmodic cough.Headache and nausea are usual side effectsContraindicated in asthamatic patients.

Peripherally acting antitussive agent are acting through inhibition of cough receptor or pulmonary stretch receptor as

Inhibition of cough receptor ofPharynx: demulcent and soothing pastilles, and

garglesLarynx: emollient and soothing spray of

menthol and eucalyptusTracheobronchial airway: inhalation of hot

steam medicated with tr. Benzoin co.

Inhibition of pulmonary stretch receptor of alveoli: benzonanatete “tesselone” Chemically related to tetracaine.MOA :Reduces the cough reflex by

anesthetizing the stretch receptors in the respiratory passages, Lungs and Pleura.stop nerve transmission to cough center.

It has some central effects also. Benzonatate begins to work within 15 to 20

minutes, and its effects last for approximately 3 hours.

Adverse effects:Headache, DizzinessNasal Congestion, burning of eyes & tightness in chest.