This document discusses terms related to pain and provides guidelines for pain management. It defines types of pain such as acute, chronic, neuropathic, and nociceptive pain. It describes the WHO analgesic ladder for treating cancer pain with non-opioids, weak opioids, and strong opioids depending on pain severity. It discusses the pharmacology and use of various analgesics like paracetamol, NSAIDs, opioids, corticosteroids, antidepressants, anticonvulsants, and others to treat different pain types and as adjuvants. It addresses myths and concerns around opioid use and emphasizes the importance of individualized treatment.

1. Pharmacology of pain
Dr. Turyahikayo jack
Palliative care unit

2. Clinical Terms For The Sensory
Disturbances Associated With Pain
• ANALGESIA: absence of pain in response to stimulation
which would normally be painful.
• ACUTE PAIN: usually due to a definable acute injury or
illness.
• BREAKTHROUGH PAIN: a transitory exacerbation of
pain that occurs on background of otherwise stable and
controlled pain.
• CHRONIC PAIN: results from a chronic pathological
process.
Pocket guide for Pain management in Africa

3. Clinical Terms For The Sensory
Disturbances Associated With Pain
• INCIDENT PAIN: pain that occurs in certain circumstances
e.g. during movement
• NEURALGIA: pain in the distribution of a nerve
• NEUROPATHY: a disturbance of function of pathological
change in a nerve
• NEUROPATHIC PAIN: pain which is transmitted by a
damaged nervous system; partially opioid sensitive
• NOCICEPTOR: a receptor preferentially sensitive to a noxious
stimulus

4. Clinical Terms For The Sensory Disturbances
Associated With Pain
• Dysesthesia – An unpleasant abnormal sensation,
whether spontaneous or evoked.
• Allodynia – Pain due to a stimulus which does not
normally provoke pain, such as pain caused by light
touch to the skin
• Hyperalgesia – An increased response to a stimulus
which is normally painful
• Hyperesthesia - Increased sensitivity to stimulation,
excluding the special senses. Hyperesthesia includes
both allodynia and hyperalgesia, but the more specific
terms should be used wherever they are applicable.

5. Aims of chronic pain mgt
• Prompt relief of pain
• Prevention of pain recurrence

6. • Optimal pain management includes drug
therapy with the analgesic drugs in
addition to non-pharmacological methods
and addressing non-physical pain.
• Types of analgesics
• Non-opioids
• Opioids
• Adjuvants

7. Principles of analgesia
Correct use of By the ladder
analgesics should be
based on the
following principles;
By the clock
-By the mouth

8. cotd
-By the individual
-Use of adjuvants

9. By the clock
SIDE EFFECTS: Drowsiness
Morphine dose By the clock
Too High
PRN
PAIN

10. • Expert committee by
the cancer and
palliative care unit of
WHO proposed a
structured approach
to drug selection for
cancer pain known as
the ‘WHO analgesic
ladder’
• Controls pain in 70-
90%

11. • The choice of analgesic depends on;
• Type of pain i.e nociceptive vs neuropathic pain.
• Severity of pain use step 1 for mild pain , step 3
for severe pain. If you start on lower step and
pain doesn’t improve go up the ladder
• Co morbidities
• Reassess pain always to find out if you can go
up or down the ladder.
• Treat underlying cause (eg, radiation for a
neoplasm, antibiotics, antifungal for
opportunistic infections)

12. Pharmacology of pain

13. Nociception
Cortex
Thalamus
Spinal
Cord
Receptor
09/13/12

14. • Paracetamol (step 1 Increased risk of
analgesic) hepatotoxicity in;
Centrally acting non- • old age
opioid,it inhibits cyclo- • Poor nut.status
oxygenase in brain • Fasting
and reduces • Chronic alcohol use
production of
prostanoids. • Conc. Use of enzyme
inducing drugs
Max dose /day= 4g/day

15. • Paracetamol (step 1 Increased risk of
analgesic) hepatotoxicity in;
Centrally acting non- • old age
opioid,it inhibits cyclo- • Poor nut.status
oxygenase in brain • Fasting
and reduces • Chronic alcohol use
production of
prostanoids. • Conc. Use of enzyme
inducing drugs
Max dose /day= 4g/day

16. NSAIDS
Examples of NSAIDS
• Ibuprofen 400mg 8 hrly max 2.4 g/d
• Diclofenac 25-50mg 8hourly max 150mg/d
• Indications :As a group, NSAIDs are of benefit for pain
due to inflammation and bone pain. They also lower
fever.
Side effects;
• ankle oedema, renal failure, can injure the gastric
mucosa and cause platelet dysfunction
• Avoid in above conditions, liver disease and bleeding.
Use with Caution in elderly. Avoid aspirin use in
asthmatics

17. Opioids
Examples; codeine, tramadol,morphine ,fentanyl
Morphine pharmacology
• If Taken orally, absorbed upper small bowel, under goes
first pass metabolism in liver and metabolized into M3G
and M6G.Half life 2-3 hrs, duration of analgesia 4-6 hrs.
• Excreted through the kidneys
• Agonist at opioid receptors (μ,κ,δ)found in the brain and
spinal cord. Analgesia is mainly mediated through the
μ receptors.
• Opioid receptors are found pre and post synaptically with
the former dominating and when opioids bind on the
former they inhibit the release of neuro transmitters.

18. Pla
sm IV
a
Co
SC/IM
nce
ntr
ati
on
po / pr
0
Half life time

19. Morphine continued
Side effects Toxicity and over dose
• Constipation- • Signs of morphine toxicity
• Nausea and vomiting and over dose include;
• Drowsiness that does not
• Drowsiness- may occur in
the first few days, if it improve
does not improve after • Confusion
about 3 days cut down on • Hallucinations
dose of morphine. • Myoclonus (sudden
• Itching- less common jerking of the limbs)
• Respiratory depression
(slow breathing rate)
• Pin point pupils

20. Myths about oral morphine
• Respiratory depression;
• This is not common if morphine doses are
titrated against pain as pain is a
physiological antagonist to respiratory
depression.

21. Tolerance
“If I take it now, what will I take when I really
need it?”
• The need for increasing doses of morphine is
usually related to disease progression.
• Reassure the patients there is adequate scope
to treat more severe pain if it occurs. There is no
maximum dose of morphine.

22. Addiction
– Differentiate addiction from physical
dependence which is a normal
physiological response to chronic opioid
use
– Psychological dependence
-Compulsive use
-Loss of control over drugs
-Loss of interest in pleasurable activities

23. …addiction
• Consider
– substance use (true addiction)
– pseudo-addiction (under treatment of pain)
– behavioral / family / psychological disorder

24. cotd
• Morphine hastens death;
• morphine can be used for many months
and years and is compatible with a normal
life style. It can only lead to death by
causing respiratory depression if given not
correctly and not orally.

25. Pain not very responsive to opioids
• 1.Neuropathic pain
• 2. Bone pain

26. Adjuvant analgesia
• These are drugs which were not designed as
analgesics but help in some types of pain along
side standard analgesics. They include;
• Antidepressants
• Anticonvulsants
• Corticosteroids
• Antispasmodics/smooth muscle relaxants
• Skeletal Muscle relaxants
• bisphosphonates

27. corticosteroids
• Dexamethasone commonly used
• Indications; bone pain, neuropathic pain from
infiltration or compression of neuronal
structures, raised ICP, athralgia, pain due to
obstruction of a hollow viscus.
• Mechanism of action; ↓peritumoral oedema ,may
reduced concentrations of PGs and LKs
• Metabolized by cyt system. Can increase
metabolism of cbz. Phenytoin increases levels of
dexamethasone

28. antidepressants
• Amitriptilline, imipramine (start with12.5-25 mg
nocte)
• Indication: neuropathic pain
• Mode of action: facilitate one or both of the 2
descending spinal inhibitory pathways by
blocking presynaptic re-uptake of serotonin or
noradrenaline
• Sideffects; dry mouth,
drowsiness,constipation,cardiac toxicity,
othostatic hypotension.
• Use with caution in elderly and cardiac disease

29. anticonvulsants
• Indication: neuropathic pain
• CBZ 100-200mg bd
• Phenytoin 300mg od
• CBZ induces liver enzymes that are responsible
for its metabolism
• Phenytoin is a hepatic enzyme inducer
• Mechanism of action; suppress paroxysmal
discharges and their spread from site of origin,
and reduce neuronal hyper excitability.
• Side effects: sedation, dizziness,unsteadiness

30. Smooth muscle relaxants
• Hyoscine butylbromide commonly used
• Indication; colicky pain
• Mode of action: in the gut reduces the
propulsive and non-propulsive gut motility
and decrease intraluminal secretions.
• Side effects: anticholinergic effects

31. Skeletal muscle relaxants
• Indication; muscle spasms
• Drug ; baclofen
• Mode of action: agonist at the gamma
aminobutyric acid receptor
• Sideeffects:
sedation,drowsiness,nausea,hypotonia.
• diazepam

32. Bisphosphonates
• Indication: bone pain not responding to
NSAIDs or radiotherapy
• Drug; pamidromate sodium
• Mode of action: reduce osteoclastic
activity in bone.

33. The message …
• between the painful part
and the patient’s experience of pain
lies the nervous system
• the nervous system is a learning system
• pain is more than a nerve activation

34. • Thank you for listening