Opioid Analgesics Flashcards by Benedicta Darko

Q

Acute pain?

A

Excessive noxious stimulus giving rise to an intense and unpleasant sensation

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Q

Chronic pain?

A

Association with the aberration of normal physiological pathways, giving rise to
- hyperalgesia (an increase amount of pain associated with a mild noxious stimulus)

allodynia (pain evoked by non noxious stimulus, loud sound)

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Q

Types of pain

A

Somatic pain
Visceral
Nociceptive
Neuropathic

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Q

Classification of analgesics

A

Opioids / Narcotic
Non opioid/ non narcotics/ nsaids

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Q

Classification of Opioid analgesics

Natural

A

Natural
Phenanthrenes - morphine, codeine & thebaine

Benzoisoquinones - papaverine, noscapine

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Q

Classification of Opioid analgesics

Semisynthetic

A

Semisynthetic
Diacetylmorphine, Pholcodeine

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Q

Classification of Opioid analgesics

Synthetic

A

Synthetic
Pethidine, fentanyl, methadone, dextropropoxyphene, tramadol, sufentanil, remifentanil

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Q

Opioid receptors

A

Cns distribution is not uniform
They are at areas concerned with pain
Receptor locations beginning with highest concentration areas

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Q

Opioid receptors

A

Cerebral cortex
Amygdala
Septum
Thalamus
Hypothalamus
Midbrain
Spinal cord

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Q

Opioid receptors

A

U(mu)
K(kappa)
Delta (Q)

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Q

Receptor stimulation

U(mu)

A

U(mu)
Physical dependence
Euphoria
Analgesia
Respiratory depression
Sedation
(PEARS)

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Q

Receptor stimulation

K(kappa)

A

Respiratory depression
Analgesia (spinal)
Miosis
Sedation
(RAMS)

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Q

Receptor stimulation

Delta

A

Analgesia (spinal & supra spinal)
Reduced GI motility

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Q

Opium

Active constituent

A

Active constituent : Morphine

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Q

Morphine - pharmacological actions

CNS depressant effects

A

Analgesia
Sedation
Euphoria
Respiratory depression
Cough suppression
Hypothermia

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Q

Morphine - pharmacological actions

CNS stimulatory actions

A

CTZ - nausea and vomiting
Edinger Westphal nucleus (III CN) - miosis
Canal centre - bradycardia
Convulsions

Q

Morphine - pharmacological actions

CVS

A

Vasodilation and fall in BP

Q

Morphine - pharmacological actions

GI effects

A

Increase in tone and decrease in motility leads to constipation

Q

Morphine - pharmacological actions

Biliary tract

A

Marked increase in the pressure in the biliary tract increase due to contraction of the sphincter of Oddi

Q

Morphine - pharmacological actions

Urinary bladder

A

Increase tone of urethral sphincter - urinary retention

Q

Morphine - pharmacological actions

Bronchial muscle

A

Histamine release-bronchoconstriction

Q

Morphine - pharmacological actions

Uterus

A

Contraction of uterus can prolong labor

Q

Morphine- Pharmacokinetics

Absorption & distribution

A

Orally, absorption is slow
Given SC/ IV/ IM
* Crosses the placental barrier
CNS is primary site of action (analgesia/sedation)

Q

Morphine- Pharmacokinetics

Metabolism and excretion

A

*Metabolic transformation in liver
*conjugated with glucuronic acid
* excreted by kidney
Half life is 2.5 to 3 hrs (does not persist in body tissue)
*morphine-3-glucuronide is main excretion product-neuroexcitatory
*morphine-6-glucoronide has prolonged opioid action

Morphine administration

Oral morphine not preferred due to erratic oral availability IV morphine acts promptly and its main effect is at the CNS Can be given IM,SC, intra- thecal

AE of Morphine

Nausea, vomiting, constipation, urinary retention Sedation, confusion, mental clouding, blurry vision Respiratory depression Hypotension Allergic reactions Drug dependence Drug tolerance Acute morphine poisoning

Tolerance to morphine

Nausea, analgesia, sedation, respiratory depression, cardiovascular, euphoric

Tolerance to morphine NOT TO

Miosis & Constipation

Drug Dependence Morphine Withdrawal

Irritability, lacrimation, sweating, *yawning, gooseflesh, restlessness, mydriasis, diarrhoea, rise in BP

Drug Dependence Morphine

Treatment Hospitalisation Gradual withdrawal of morphine *substitution therapy with methadone- given orally, long acting * opioid anatagonist like Naltrexone Psychotherapy, community treatment and rehabilitation

Drug interactions with opioids

In general, the co administration of CNS depressant with OPIOID often produces at least an additive depression (potentiation)

Precautions/ Contradictions

Avoid in infants and elderly Avoid in bronchial asthma *Avoid in head injury -vomiting, Miosis, mental clouding- interferes with assessment of progress in head injury patients - Respiratory depression- causes co2- cerebral vasodilation- Increases intracranial pressure Avoid in hypotension states Undiagnosed acute abdominal pain

Acute morphine poisoning

Pinpoint pupil, respiratory depression and coma Other manifestations: cyanosis, hypotension, shock & convulsions maybe seen in few Death due to respiratory failure

Acute morphine poisoning Treatment

Hospitalisation Maintain airway, breathing and circulation Ventilatory support Gastric lavage with potassium permanganate

Acute morphine poisoning Treatment Specific antidote

Naloxone 0.4-0.8 mg. IV dose is repeated till respiration becomes normal

Codeine (Methyl-morphine)

Natural opium alkaloid Weak analgesics Given orally well absorbed from GI tract Less respiratory depressant effect Low addiction liability Less constipation High cough suppressant effects Relief of mild to moderate pain

Pethidine moa

Synthetic opioid agonist Orally absorbed, widely distributed