pain definition , history , terms epidemiology, pain receptors , types ,pathogenesis, pathways of pain , examples, lab investigations,pain assesment tools, treatment

1. T.Sai Swapna
II/VI Pharm .D
Nirmala College Of
Pharmacy

2. 
 An unpleasant sensory and emotional experience
associated with actual or potential tissue damage
 Other manifestations of pain related to tissue injury
include hyperalgesia , allodynia
 It is almost UNIVERSAL experience
 It is associated with more or less dicomfort , distress ,
resulting from the specific stimulation of specilalized
nerve endings
Definition ;

3.  Pain is derived from latin word POENA meaning
“punishment from the god “.
 Cola was intially used to cure pain , using caffeine as
pain reliever
 Hippocrates was the first person introduced active
ingredient that is ASPIRIN now a days using as
NSAIDS
 Queen victoria was the first one taken anathesia for
pain control during childbirth ; chloroform is used
History;

4. 
 Allodynia ; pain due to non – noxious stimulus to
normal skin.
 Analgesia ; absence of pain on noxious stimulation
 Anaesthesia Dolorosa ; pain in a area or region
which is anaesthetic.
 Causalgia ; a syndrome of sustained burning pain
after a traumatic nerve lession combined with
vasomotor and sudomotor dysfunction
Terms ;

5. 
 Central pain ; pain associated with a lesion of the
central nervous system.
 Dysaesthesia ; an unpleasant abnormal sensation
 Hyperalgesia ; increased sensitivity to noxious
stimulation
 Hyperaesthesia ; increased sensitivity to stimulation
excluding special senses
 Hyperpathia ; a painful syndrome characterisied by
delay over reaction and after sensation to stimulus
 Hypoalgesia ; diminshed sensitivity to noxious
stimulation
Terms ;

6. 
 Hypoaesthesia ; decreased sensitivity to stimulation
excluding special senses
 Neuralgia ; pain in the distribution of nerves
 Neuritis ; inflammation of nerve
 Neuropathy ; a disturbance of function or
pathological change in a nerve
 Nociceptor ; a receptor preferentially sensitive to
noxious stimulus
 Pain threshold ; the least stimulus intensity at which
a subject persives pain
Terms ;

7. 
 According to the american pain foundation , more
than 50million people in the US suffer from chronic
pain.
 An additional 25% , 20 million experience acute pain
from injury or surgery
 The annual incidence of moderate – intensity back
pain is 10% - 15% in the adult population with a
point prevalance of 15% - 30%
 The national institute for occupational safety and
health estimated that the cost of low back pain alone
was between 50 billions – 100 billions per year
Epidemology ;

8. 
Classification of pain ;

9. 
 Acute pain has sudden onset,usually subsides
quickly and is characterised by sharp , localised
sensations with an identifiable cause
 Last > 30 days associated with muscles strains and
tissue injury such as trauma
 A poorly treated pain can cause psychological stress
and compromise the immune system due to the
release of endogenous corticosteroids
Acute pain;

10. 
 Acute pain is usually characterised by increased
autonomic nervous system activity resulting in
Psychological symptoms such as
anxiety
Tachypnoea
Tachycardia with hypertension
Pallor
Diaphoresis
Pupil dilation
Acute Pain

11. 
 Viseral pain is a type of nociceptive pain that comes
from the internal organs
 Unlike somaatic pain it is harder to pinpoint
 Pain is described as general aching or squeezing pain
 It is caused by the activation of pain receptors in the
chest, abdomen or pelvic areas
 In cancer patient pain is caused by tumour
infiltration, constipation, radiation & chemotherapy
Visceral Pain

12. 
Somatic pain ;
 Superficial pain ;
 It is also known as CUTANEOUS
PAIN
 Arises from superficial
structure's as skin &
subcutaneous tissues
 It is sharp bright pain with a
burning quality and may be
slow in onset
 Deep somatic pain ;
 It orginates in deep body
structures such as peristeum ,
muscles , tendons , joints &
blood vessels
 Strong pressure , ischemia ,
tissue damage act as stimuli for
this pain .
 Radiation of pain from original
site of injury occur

13. 
 Chronic pain is pain long lasting longer than 3 to 6
months
 It begins when pain persists after the initial injury
has healed
 It adversely effects the function and wellbeing of
patient
 It may be nociceptive , inflammatory , neuropathic or
functional in origin
Chronic pain ;

14. 

15. 
 Main effects of chronic
pain ;
 Effect on physiological
function
 Psychological changes
 Social consequences
 Contributing factors ;
 Peripheral mechanisms
 Peripheral central
mechanisms
 Central mechanisms

16. 
 Peripheral mechanisms ; + of peripheral nociceptors ,
contribute to pain associated with chronic
muscoskeletal , visceral , vascular disorders
 Central mechanism ; associated with injury disease
of CNS; characterised by burning , hyperalgesia ;
associated with spinal cord injury , multiple sclerosis
 Peripheral – central mechanisms ; abnormal function
of both peripheral portions associated with loss of
descending inhibitary pathways
Contributing factors

17. 
Chronic pain types ;
 Chronic malignant
pain;
 It occurs in 60 – 70% of pt’s
with cancer
 Pain may be related to cancer
therapy / tumour
 Pain may be somatic and
visceral
 Chronic non –
malignant pain ;
 Pain lasts for many years and
progressive in nature
 May be nociceptive ,
neuropathic , or mixed in
nature .

18. 
Types of non malignant chronic pain ;
 Neuropathic pain;
 it is a result of an injury of
the nervous system
 Described as aching
 Burning
 Shooting
 Stinging
 Tenderness / sensitivity to
skin
 Musco skeletal pain ;
 Occurs due to
musculoskeletal disorders
such as
 Rheumatoid arthritis
 Osteoarthritis
 Fibromyalgia
 Peripheral neuropathies

19. 
Based on transmission;
FAST PAIN
 Lasts about 0.1 sec after pain
stimulus is applied
 It is described as sharp pain ,
acute & electrical pain
 It is not felt in deeper tissues of
the body
SLOW PAIN
 Begins after 1 sec or more and
many range from seconds to
minutes
 Described as slow , burning ,
aching , nauseous and chronic
pain
 Associated with tissue
destruction

20. 
OTHERS TYPES OF PAIN
REFERRED PAIN
 Pain that is perceived at the site
different from its point of origin
 Pain from viscera
 Eg ; pain associated with MI
commonly is referred to the left
arm , neck , chest
BREAKTHROUGH PAIN
 Pain is intermittent , transitory
& an increase in pain occurs at
a greater intensity
 Usually lasts from minutes to
hours
 Eg ; neuropathic pain
 lower back pain

21. 
 Also called NOCICEPTORS
 Thers are sensory receptors that are activated by
noxious insults to peripheral tissues
 These receptors are widely ditributed in the
 Skin
 Dental pulp
 Periosteum
 Meninges
Pain receptors ;

22. 
Nerve fibers involved in pain
transmission
Nerve fibers
A fibres
A- BETA Fibres
A- DELTA Fibres
C fibres

23. 
A Fibres ;
A Beta fibres
 Large
 Myelinated
 Fast conducting
 Low stimulating threshold
 Respond to light touch
A Delta fibres
 Small
 Lightly myelinated
 Slow conducting
 Respond to heat , pressure ,
cooling , & chemicals
 Sharp sensation of pain

24. 
 Small and unmyelinated
 Very slow conducting
 Respond to all types of noxious stimuli
 Transmit prolonged dull pain
 Require high intensity stimuli to trigger a response
C Fibres

25. 
Pathways of pain ;

26. 
Descending pathway ;

27. 
 It includes four distinct processes ;
 Transduction
 Transmission
 Modulation
 Perception
Pathophysiology of pain ;

28. 
 Process by which noxious stimuli lead to electrical
activity in sensory nerve endings
 Speciliazed receptors distributed all over the body
which respond to physical & chemical stimuli
 They are 1 . Extroreceptors
 2 . Proprioseptors
 3 . Interoseptors
Transduction ;

29. PROPRIOSEPTORS ;
sensory receptors provides
information from musculoskeletal
structures
Eg ; pacinian corpuscles ; receptors
concerned in the preception of
pressure
EXTROCEPTORS ;+ by immediate
external environment
 Provide information from skin
& mucosa
 Eg; Meissner’s corpuscles ;
tactile receptors on skin
 merkel’s corpuscles ; tactle
receptors in submucosa of
tongue and oral mucosa INTEROSEPTORS ;
Sensory receptors located and transmit
impulses from the viscera of the body
Sensation from these receptors are
involved in the involuntary
functioning of the body
Eg ; free nerve endings ; perceive
visceral pain and other sensation

30. 
 Neural events that carry the nociceptive input into the CNS
 1) PERIPHERAL SENSORY NERVE ; Primary afferent neuron carries
nociceptive input from sensory organ into the spinal cord
 2) SECOND ORDER NEURON ; Carries input to the higher centers
through spinal cord
 3) THIRD ORDER NEURON ; Interaction of neurons between the
thalamus cortex and the limbic system as the nociceptive input reaches
these higher centers
Transmission ;

31. 
 PERCEPTION ; Reaching of the nociceptive input to the cortex is
perception
 It is at this level suffering & pain behaviour begins
MODULATION ; Ability of the CNS to control the pain transmitting
neurons
several areas of brain & cortex have been identified that can either enhance
or reduce nociceptive input

32. 

33. 

34. 
 ACUTE PAIN ; Tachycardia , diaphoresis , mydriasis
, pallor
 CHRONIC PAIN ; acute cases become severe then
chronic pain occurrs no obvious signs
 LABORATOTY TESTS ;
 Pain is always subjective there are no laboratory tests
 It is diagnosed based on patients description and
history
Signs of pain ;

35. 
 Comprehensive history intake ;
 Medical history
 Physical history
 Family history
 Questioning on characteristics of pain – onset ,
duration, location , severity , intensity
 Evalution of pschycological status
Assesment of pain ;

36. 
 P - Palliative
 Q - Quality
 R - Regon / Radiation
 S - Severity
 T - Time related
Pain assesment

37. 
Pain assesment tools ;
 RATING SCALES ;
 Provide a simple way to
classify the intensity of pain
and should be selected based
on patients ability to
communicate
 Simple descriptive pain
intensity scale
 Visual analog scale
 Faces scale
 Verbal rating scale
 Pain thermometer
 MULTIDIMENSIONAL
SCALES ;
 Helpful in obtaining
information about pain but
time consuming to assess
 Brief pain inventory
 Neuropathic scale
 The oswestry disability index

38. 

39. 
Pain thermometer;

40. 
 Opioids ; morphine , fenatyl
 Local anesthetics ;
 NSAID’S; ibuprofen , aspirin procaine , mepivacaine
 Alpha 2 adrenergic agonists ; clonidine
 NMDA Antagonists ; ketamine ; methoxetamine
 Others ; GABA Pentin , Tramadol
General classes of analgesic drugs;

41. 