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Treatment, P2S2 > Lecture 4 - Anlagesic and Gut Motility Drugs > Flashcards

Lecture 4 - Anlagesic and Gut Motility Drugs Flashcards

1
Q

Pain Assessment

Comment on difficulties

What the patient must address

No response to treatment??

A
  • Pain is hard to describe
  • Clinicians may underestimate pain
  • NEED to listen to what and how tha patient is describing their pain
  • Characterise the pain
  • Identify the underlying mechanism/cause
  • Assess the effect on the patient’s functioning and quality of life

*If the patient is not responding, re-evaluate the patient for any missed causes*

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2
Q

What type of assesment can be used to help the patient describe the pain?

Give Examples.

A

Pain Assesment Scales

1) Simple Descriptive Pain Intensity Scale
2) Numeric Rating Scale
3) Visual Analogue Scale

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3
Q

How is pain classified?

Give Examples

A

1) Nociceptive Pain

Tissue Damage

  • Somatic
    • Well localised, throbbing, ache
    • Metastatic bone pain
  • Visceral
    • From the stretching or expansion of hollow organs
    • Signals carried by the ANS
    • NOT as well localised
    • Often referred pain
      • Ex. Left shoulder pain caused by irritation of the right diaphragm caused by enlarged liver
    • Liver Capsule Pain
      • Presents as continous aches, dull
    • Malignant bowel obstruction
      • Colic Pain

2) Neuropathic Pain

  • Nerve Damage
    • Central/Local
  • Presents:
    • Dysaesthetic (burning)
    • Lancinating (sharp pain)
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4
Q

Describe the WHO Pain ladder

Address the appropriate treatment for each step

A

1) Aceteminophen, NSAIDS, Asprin
2) Codeine, Percocet, Percodan
* Combinations of Oxycodone with acetaminophen or aspirin
3) Morphine, Hydromorphone, Oxycodone, Methadone, Fentanyl
* DO NOT USE Meperidine

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5
Q

Draw the Analgesic Arrow

A
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6
Q

Paracetemol

Classification

Mechanism

Mode of Action

Indications

Adverse Effects

A
  1. Classification
  • Analgesic
  • Antipyretic
  • NOT an NSAID​

2. Mechanism

  • Inhibits PG synthesis via COX-3 (CNS)
  • DOES NOT PROMOT
    • GI ulcers
    • Bleeding
    • Renal Failure
  • Peripherally blocks generation of pain impulses
  • Inhibits hypothalamic heat-regulation centre

3. Mode of Action

  • Analgesic
  • Weak PG inhibitor

4. Indications

  • Mild/Moderate pain w/o inflammation

5. AE

  • Rare at normal dosage
  • Caution in liver failure/underweight
  • Liver/Renal toxicity with overdose
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7
Q

Paracetmol

Modes of metabolism

A
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8
Q

Opiate: Analgesics

1) Source
2) Principal Alkaloids
3) Classification

A

Source

  • Seed pods of opium poppy

Prinicipal Alkaloids

  • Morphine
  • Codeine

Classification

  • Full Agonist = High Efficacy
  • Partial Agonist = Weaker analgesia
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9
Q

Terminology

Opium

Opiate

Opiod

A
  1. Greek word meaning juice or exudate from the poppy
  2. A drug extracted from the exudate of a poppy
  3. Natural or synthetic drug that binds to opiod receptors producing agonist effect
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10
Q

What are the 2 sources of Natural Opiods?

Where are the rest derived from?

A

Sources:

1) The juices of the opium poppy (morphine and codeine)
2) Endogenous Endorphins

Remainder

  • Prepared from Morphine
    • Semisynthetic drugs such as heroin
  • Synthesised from Precursor compunds
    • Fentanyl
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11
Q

What are the Pharmacological Effecs of opiods?

A

1) Sedation and Anxiolytic

2) Depressed Respiration

  • Main cause of death from opiod overdose
  • Combination of OPIODS and ALCHOL = BAD

3) Cough Supression

4) Pupillary Constriction

5) Nausea and Vomitting

  • Stimulation of receptors in an area of the medulla called the chemoreceptor trigger zone
  • Causes nausea and vomitting

6) GI

  • Can relieve diarrhoea

7) Other

  • Opiods release histamines causing itching or more severe allergic reactions including bronchoconstriction
  • Affect white blood cell function and immune function
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12
Q

What is the mechanism of action of Opiods

A
  • Activation of peripheral nociceptive fibers causes release of substance P and other pain-signaling neurotransmitters from nerve terminals in the dorsal horn of the spinal cord
  • Release of pain-signaling neurotransmitters is regulated by endogenous endorphins or by exogenous opioid agonists by acting presynaptically to inhibit substance P release, causing analgesia
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13
Q

What is the mode of action of Morphine?

Target

Action

Effect

Overall Effect

A

Target:

G- Protein coupled opioid mu receptors in the CNS or peripheral nervous system

Action:

Full Agonist

Effect:

  • Closure of N-type, voltage dependent calcium channels
  • Opening of calcium dependent inward;y rectifiying Potassium channels,
    • Increased k+ conductance
  • Also Inhibit the release of substance P
    • Pain signalling neurotransmitter

Overall Effect:

  • Membrane hyperpolarization
  • Reduced neuronal excitabilty
  • Reduction/Inhibition of pain NT signals
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14
Q

What are the 3 of Opiod receptors?

Explain the differences

A
  1. mu
  2. Kappa
  3. Delta
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15
Q

Describe the differences between the 3 subtypes of the mu receptor

A

Mu 1

  • Central interpratation of pain

MU 2

  • Respiratory Depression
  • Spinal Analgesia
  • Euphoria
  • Dependence

MU 3

  • Only Opiod alkaloids
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16
Q

Further Explain the kappa receptor

A
  • Only modest analgesia
  • Little or no respiratory depression
  • Little or no dependence
  • Dysphoric effects
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17
Q

Further explain the delta receptor

A
  • It is unclear what delta’s responsible for
  • Delta agonists show poor analgesia and little addictive potential
  • May regulate mu receptor activity
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18
Q

What is the expected response if an Opiod binds to a MU receptor

A

ANALGESIA

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19
Q

What is the expected response if an opiod binds to a Mu2

A
  • Analgesia
  • Respiratory Depression
  • Euphoria
  • Decrease GI motility
  • Physical Dependance
20
Q

What is the expected response if an opiod binds to a KAPPA receptor

A
  • Analgesia
  • Dysphoria
21
Q

Prescribing Opiods

  1. Weak Opiods
  2. Strong Opiods
  3. Do NOT use
A

1. Weak

  • Dose often
  • Codeine limited by presence of paracetmol and constipation
  • Tramadol
    • Caution in elderly and those on SSRI

2. Strong

  • Morphine
  • Oxycodone
  • Fentanyl
  • Diamorphine
  • Hydromorphone
  • Methadone
  • Buprenorphine

3. DO NOT USE

  • Pethidine
22
Q

What are the differences between opiods?

A
  • Loads of inter and intra-individual variability in response to opiods
    • Analgesic Response
    • Side Effect responses
23
Q

Principles of Dosing Opiods

What is the goal?

A

The right dose is the one that achieves the best analgesia with the least side effects.

24
Q

Opiod Formulations

Discuss the options

Comment when to use either or

A

1) Short Acting

  • Opiod-naïve patients
  • Pain crisis

2) Long Acting

  • For stable situations
  • Can add a SA for breakthrough pain episodes
25
Q

Pharmackinetics of Opiods

a) onset of pain relief
b) duration of pain relief
c) half life of transdermal fentanyl

A

Onset of pain relief

– Oral opioids 15 - 30 min

– SC opioids 5 - 10 min

– IV opioids 3 - 5 min

Duration of pain relief

– Short-acting oral opioids 3 - 5 hours

– Long-acting oral opioids 8 - 12 hours

– Fentanyl patches 48 - 72 hours

– IV or SC opioids 2 - 4 hours

– IV/SC fentanyl 40 minutes

Half-life of transdermal fentanyl

– 12 to 24 hours

26
Q

How can one calculate the breakthrough dose?

A
  • Equivalent to a 4 hourly dose
  • May need to titrate dose according to patient needs: 5% to 25% of total daily opioid dose
  • Generally use the same opioid as being used for regular regimen (except with fentanyl patches)
27
Q

Contraindication of Opiods

A

Patients with…

  • Impaired pulmonary function
  • Impaired hepatic and/or renal function
  • Hypothyroidism
  • Recent head injury
28
Q

Clincial Uses of Opiods

A
  • Analgesia for severe visceral pain
  • Acute pulmonary edema
  • Cough suppression
  • Diarrhoea
  • Pre-medication
  • Regional anaesthesia
29
Q

Tolearance in Opiods

What is it?

Demonstrated by…

Physiological Tolerance…

Will it occur with Opiods?

A
  • A diminished responsiveness to the drug’s action that is seen with many compounds
  • Demonstrated by a decreased effect from a constant dose of drug or by an increase in the minimum drug dose required to produce a given level of effect
  • Physiological tolerance involves changes in the binding of a drug to receptors or changes in receptor transductional processes related to the drug of action
  • This type of tolerance occurs in opioids
30
Q

Physiological Dependance

Withdrawl Reactions?

A
  • Occurs when the drug is necessary for normal physiological functioning – this is demonstrated by the withdrawl reactions
  • Withdrawl reactions are usually the opposite of the physiological effects produced by the drug
31
Q

Define Withdrawl

Give Examples of Acute effects and Withdrawl Signs

A

Withdrawl gives the opposite effect of the drugs physiological effect

Acute

Analgesia

Respiratory Depression

Euphoria

Relaxation and sleep

Tranquilization

Decreased blood pressure

Constipation

Pupillary constriction

Hypothermia

Drying of secretions

Reduced sex drive

Flushed and warm skin

Withdrawl

Pain and irritability

Hyperventilation

Dysphoria and depression

Restlessness and insomnia

Fearfulness and hostility

Increased blood pressure

Diarrhoea

Pupillary dilation

Hyperthermia

Lacrimation, runny nose

  • Spontaneous ejaculation
  • Chilliness and “gooseflesh”
32
Q

Give an example of an opiod antagonist

Use?

Affinity?

MOA?

A
  • Naloxone
  • Opioid antagonists are used to treat opioid overdose
  • Strong binding affinity for the Mu receptor
  • Work by competitive inhibition site blocking agonist activity
33
Q

Management of Narcosis

What is Narcosis?

How to recognise?

What to do if they ar uncoscious or in resp. depression?

A

Narcosis: Excess opiods

Suspect the diagnosis in any patient with small pupils.

*If the patient is unconscious or has respiratory

depression:

  • Ensure a clear airway (ABCDE)
  • Give naloxone iv every two minutes until the patient improves or until eight doses have been given.
  • Check blood sugar
34
Q

What to remember if the patient responds to Nalaxone

A

RECAP: Nalaxone = Opiod antagonist

  • Relapse is likely after about 20 - 30 minutes.
  • Withdrawal effects can be precipitated .
  • Infusion of naloxone may be required if relapse occurs.
35
Q

Methods of Relieving Pain

A

Remove peripheral stimulus

  • E.g. Treat infection / tooth extraction / NSAIDs

Interrupt nociceptive input

  • NSAIDs / local anaesthetic / neurectomy

Stimulate nociceptive inhibitory mechanisms

  • Electrical (TENS) / Heat

Modulate central pain awareness

  • Opiates / General anaesthetics / Psychotropics

Treat secondary factors contributing to pain

  • Muscle spasm (relaxants)
36
Q

Summary #1

A
  • There are different types of opioids with varying potencies
  • They are very effective general pain relievers for moderate-severe pain but have a lot of adverse effects (some of which are serious)
  • They don’t have any anti-inflammatory properties and therefore are less ideal in inflammatory pain
  • If someone becomes narcosed (too much opioid) then this can be reversed by a competitive antagonist Naloxone – but care is needed due to shorter duration of action
37
Q

Mechanisms of Nausea and Vomitting

A

Brain Cortex

  • GABA
  • Anxiety
  • Anticipatory Nausea

Vestibular Appartus

  • Histamine
  • Motion Induced

Vomitting Centre

  • AcH
  • Dopamine

GI tract

  • Dopamine
  • 5HT3
  • Tumors
  • Obstruction
  • Distension

Chemoreceptor Trigger Zone

  • Dopamine, 5HT3
  • Drugs (e.g. chemotherapy, opioids, SSRIs)
  • Toxins (infections, etc)
  • Biochemical (e.g. hypercalcemia, uremia, etc)
38
Q

Management of Nausea

A
  • Attempt to identify the underlying cause(s)
  • Attempt to correct the underlying cause(s) if possible and if appropriate
  • Treat the symptoms
    • Anti-emetics selected according to the inferred underlying mechanisms
  • Prevent nausea
    • Employ a regular anti-emetic regimen if nausea is prolonged
    • Prevent constipation
  • If one agent not completely effective, review and add another or replace with another
39
Q

Examples of Anti-emtics?

Caution

A
  • Anti-dopamine agents (CTZ)*
    • Metoclopramide
  • 5HT3 antagonists
    • Ondansetron
  • Anti-Histamine
    • ​Cyclizine

NOTE:

*Care in young people as can cause acute dystonia

40
Q

What do Anti-emetics do?

Metclopramide SE?

A

Pro-motility and anti-dopamine agents

1) Metoclopramide

  • Extrapyramidal side effects may occur
  • Upper GI pro-motility
41
Q

Which Anti-Emetics are appropriate for palliative care?

A
  • 5-HT3 antagonists
    • Ondansetron
42
Q

Causes of Constipation

A

Other

  • Immobility
  • poor diet
  • poor fluid intake
  • increased fluid loss (e.g. vomiting, diarrhoea, fever).

Drugs

  • Opioids
  • anti-muscarinics

Local Pain

  • Anal fissure
  • peri-anal abscess.

Benign colorectal disease

Neuropathy

Malignancy - Colorectal, ovarian, and uterine tumours

43
Q

Treatment of Constipation

A
  • Increase fluid intake
  • Improve mobility
  • Increased fibre intake (unless d/t opioids)
  • Stopping constipating drugs
  • Excluding underlying pathology
44
Q

What is the MOA of laxatives

Osmotic

Fecal Softener

Stimulant

A

Osmotic

  • Macrogols
  • Lactulose
  • Promote H20 out of cells into the gut lumen
  • Large volume in bowel - enters and creates distension
  • Purgation within an hour

Fecal Softener

  • Docusate
  • Dulcolax - Sodium Picosulfate
  • Sofetenr and stimulant
  • increases GI secretions into the lumen

Stimulant laxatives

  • Bisacodyl
  • Senna
  • Stimulates eneteric nervous system to increase peristalsis and e- + H20 addition to the lumen
45
Q

Management of Constipation

A
  • Pre-empt constipation by putting everyone at risk (eg patients on opioids) on regular laxatives
  • Treat reversible causes eg give analgesia if pain on defecation, alter diet, ↑ fluid intake
  • Adjust any constipating medication, if possible.
  • Advise the person about increasing dietary fibre, drinking an adequate fluid intake, and exercise.

•Offer oral laxatives if dietary measures are ineffective, or while waiting for them to take effect.

–Start treatment with a bulk-forming laxative (Fybogel)(adequate fluid intake is important).

–If stools remain hard, add or switch to an osmotic laxative (macrogols (Movicol))

– If stools are soft but the person still finds them difficult to pass or complains of inadequate emptying, add a stimulant laxative (Ducolax (sodium picosulfate)/ enema).

If the person has opioid-induced constipation:

– Avoid bulk-forming laxatives.

– Use an osmotic laxative (macrogols (Movicol))(or docusate which also softens stools) and a stimulant laxative (Ducolax (sodium picosulfate)/ enema).

• Laxatives can be stopped once the stools become soft and easily passed again.

46
Q

Summary #2

A
  • Nausea and vomiting often has multi-factorial influences – aim to treat cause
  • Select anti-emetic based on likely cause baring in mind potential adverse effects
  • Constipation also often has multiple influences – use practical measures to reduce these
  • Different classes of laxative work synergistically
47
Q
A

Treatment, P2S2 (2 decks)

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