This is an excellent ppt on types,symptoms and drug therapy of neuralgias illustrated with pictures, flowcharts and appropriate algorithms...

15. DRUG THERAPY OF NEURALGIAS
DR.V.SATHYANARAYANAN MBBS., M.D., ACME.,
PROFESSOR OF PHARMACOLOGY,
SRM MCH & RC, CHENNAI, INDIA

16.  Definition
 Neuralgia vs Neuropathy
 Classification, Characteristics and clinical course of neuralgias
 Types of neuralgias
 Drugs for neuralgias
 Trigeminal neuralgia
 Glossopharyngeal neuralgia
 Occipital neuralgia
 Post herpetic neuralgia
 Conclusion
OUTLINE

17. WHAT IS NEURALGIA ?

19.  neuralgia refers to pain in the distribution of a nerve
 Neuropathy implies neuronal injury.
 Patients with neuralgia may or may not have a
secondary cause.
NEURALGIA VS NEUROPATHY

20.  primary (classical) or
 secondary (symptomatic)
 Distinguishing between the 2 is critical for
 developing an appropriate diagnostic and therapeutic
plan
CLASSIFICATION

21.  The neuralgias are characterized by
 paroxysmal, brief, and intense pains
 described as
 sharp,
 lancinating,
 stabbing, or
lightning-like
 within the distribution of a particular nerve.
CHARACTERISTICS

22.  They are often associated with triggers that may take the
form of trivial stimuli,
 such as brushing teeth or shaving.
 generally followed by pain-free periods known as refractory
periods.
 Tenderness over the involved nerve is typical
 as is abolishment of pain by local anaesthetic blockade
CHARACTERISTICS

24.  monophasic,
 relapsing and remitting,
 or chronic in nature..
Clinical course

25.  The most commonly encountered neuralgias are
 Trigeminal neuralgia
 Post herpetic neuralgia
 Glossopharyngeal neuralgia
 Occipital neuralgia
TYPES

27.  Carbamazepine 200 mg/day , 400–800 mg/d
 Oxcarbazepine 150 mg/d, 150 mg/3d, 750–1800 mg/d
 Gabapentin 300 mg/d, 300 mg/3–7 d, 900–2400 mg/d
 Pregabalin 150 mg/d, 150 mg/wk, 600–1200 mg/d
 Lamotrigine 25 mg/d, 25 mg/wk, 100–400 mg/d
 Topiramate 25 mg/d , 25 mg/wk , 100–400 mg/d
 Baclofen 5–10 mg/d, 5 mg/3d, 50–75 mg TID
 Amitriptyline
DRUGS FOR NEURALGIAS

29. CARBAMAZEPINE
 Chemically related to imipramine
 MOA – Prolongs the inactivated state of neuronal
voltage dependent sodium channels and stabilize
neuronal membrane
 75% protein bound
 Long half life
 Autoinduction occur

30. Sodium channels

31. ADVERSE EFFECTS
 Hypersensitivity
 Dose related neurotoxicity- drowsiness, ataxia,
vertigo
 Hypersensitivity reactions- Hepatitis, lupus like
syndrome
 Enhance ADH action
 Aplastic anemia
 Minor fetal malformations

37. USES IN NEURALGIA
1st choice in Trigeminal neuralgia ,
post herpetic neuralgia
and other neuropathic pain

40. OXCARBAZEPINE
 Less toxic than carbamazepine
 Mild enzyme inducer – less drug interactions
 Less side effects
 Cause hyponatremia

42. GABAPENTIN
 GABA derivative
 Increases GABA release
 Add on drug in SPS, CPS
 Pain due to diabetic neuropathy, post herpetic neuralgia
 Migraine
 Manic depression
 ADR- sedation, tiredness

46. PREGABALIN

50. LAMOTRIGENE
 Broad spectrum action
 Blocks Na channels  stabilizes presynaptic
membrane
 blocks high voltage dependent Ca channels
 Prevents release of excitatory neurotransmitters

52. ADVERSE EFFECTS
 Sedation,
 ataxia,
 diplopia,
 RASH –sometimes life threatening
 Negative effect on cognitive function not reported

56. TOPIRAMATE
 Weak Carbonic anhydrase inhibitor
 Broad spectrum anticonvulsant
 Act by antagonizing glutamate, GABA potentiation, prolonging
Na channel prolongation
 ADR – sedation, ataxia, psychiatric symptoms

58. BACLOFEN
 Selective GABAB receptor agonist
 Act at spinal cord
 Depress both poysynaptic, monosynaptic reflexes
 Less sedative
 Reduces spasticity in many neurological disorders
 S/E – mental confusion, ataxia, weakness

60.  Tricyclic antidepressant
 Acts by inhibiting NE and serotonin reuptake by
presynaptic neurons  increased NE in the synapse
 takes 3 to 4 weeks time for full benefit
 Widely used in neuropathic pain in low doses
 Side effects  dizziness, drowsiness, dry mouth, nausea
and constipation
AMITRIPTYLINE

64. OTHER DRUGS

65.  Clonidine is an α2-adrenergic agonist  provides potent
analgesia.
 In neuropathic pain, α2 adrenoreceptors are upregulated and
are sensitive to norepinephrine.
 Activation of α2 adrenoreceptors therefore inhibits the
release of calcitonin gene-related peptide and glutamate
role in nociception as neurotransmitters.
 Clonidine may be compounded into a cream and applied
topically to provide pain relief.
 Systemic side effects include sedation and hypotension
requiring close monitoring.
CLONIDINE

67.  5% lidocaine plasters comprised of 700 mg of
lidocaine mixed with a polyethylene terephthalate
backing.
 used 12 hours per day for 4 weeks for TN
 a lidocaine 5% patch  post-herpetic neuralgia and
other peripheral neuropathic conditions.
 Adverse effects are minimal and include erythema
and rash.
LIDOCAINE

71.  Capsaicin is a component of chili peppers.
 It binds to the nociceptor, TRPV1, which is located on
polymodal C-fibers.
 Initially capsaicin works by increasing the production of
inflammatory mediators, causing hyperalgesia.
 However, repeated application may cause prolonged
activation of the TRPV1 receptor, rendering it dysfunctional.
 Capsaicin is available at low concentrations in ove rthe-
counter creams.
 0.025% capsaicin for 3 minutes twice a day, after local
anesthetic application to the painful site
CAPSAICIN

74.  nausea, dyspepsia, and initial increase in pain when applied
topically.
 Pain relief is dose dependent and
 may last for several weeks.
 Capsaicin preparations at higher doses, (capsaicin patch 8% )
have shown to be more efficacious.
 treatment is challenged by low adherence to this medication
 due to its side effects, particularly the burning pain .
CAPSAICIN PREPARATIONS

77.  carbamazepine 4% (a sodium channel blocker)
 lidocaine 1%
 ketoprofen 4% (a non-steroidal anti-inflammatory drug, or
NSAID)
 ketamine 4% (an NMDA-receptor antagonist)
 gabapentin 4%
 These medications were mixed with anhydrous gels and
bio-adhesive copolymers
COMPOUNDED FORMULAS

78.  Cannabinoids have been identified as potential adjuvant
analgesics and are currently under investigation
 The natural cannabis plant (Cannabis Sativa L) contains more than
60 cannabinoids
 Tetrahydrocannabinol (THC)/Cannabinol(CBD) oromucosal spray
 Formulated from plant-based extracts
 treatment of central neuropathic pain in patients with multiple
sclerosis (MS),
Tetrahydrocannabinol and Cannabinol
as a Spray

84.  Brief, intense, electrical pain
 characteristically triggered by
 chewing,
 talking,
 and light touch (eg, wind).
Trigeminal Neuralgia

86.  Trigeminal neuralgia may mimic tooth pain,
 and some patients report an intraoral trigger zone.
TRIGEMINAL NEURALGIA

90.  involves the trigeminal nerve in the head.
 It has three branches that send signals from the
brain to the face, mouth, teeth, and nose.
Trigeminal neuralgia (TN)

94.  TYPE 1 AND TYPE 2
 Type 1 TN  causes a painful burning or electric shock-
like sensation in parts of the face
 irregular episodes that come on suddenly
 duration of these episodes varies
 can last up to 2 minutes.
 Type 2 TN - produces a constant, dull aching sensation
in the face.
TYPES

97.  The initial treatment of TN always involves
pharmacotherapy with carbamazepine
 (target=400–800 mg/d)
 the first-line treatment of choice.
TREATMENT

99.  Oxcarbazepine (target=900–1800 mg/d)
 is equally efficacious
 with a better side effect profile
TREATMENT

102.  often as add-on therapies, include
 phenytoin (target=300–500 mg/d),
 baclofen (target=40–80 mg/d),
 clonazepam (target=1.5–8 mg/d),
 lamotrigine (target=150–400 mg/d),
 gabapentin (target=900–2400 mg/d),
 and pimozide (target=4–12 mg/d)
OTHER DRUGS

103.  Pimozide is not widely used
due to potential cardiac and neurologic toxicity
 The clinical utility of certain agents, especially lamotrigine,
is limited by
 the requirement for a slow titration
LIMITATIONS

104.  botulinum toxin type A (BTX) INJECTION 
generally effective treatment without major adverse
events
 The optimal injection strategy is yet to be
determined
REFRACTORY CASES

108.  Opioids are sometimes used during acute
exacerbations
 rescue intravenous infusion of either fosphenytoin
or lidocaine may provide transient relief while
awaiting interventional procedures
OTHER DRUGS

112.  20% benzocaine,
 capsaicin,
 or a compounded formula of anticonvulsants,
tricyclic antidepressants, serotonin and
norepinephrine reuptake inhibitors
 applied over an intraoral trigger zone
TOPICAL MEDICATIONS

116.  reduced systemic side effects
 lessened potential for drug-drug interactions
 the ability to provide direct, local analgesia;
 and improved patient compliance
ADVANTAGES OF TOPICAL
MEDICATIONS

117. for refractory TN
 ablative (destructive)
 (eg, peripheral neurectomy,
 glycerol rhizolysis,
 sensory rhizotomy, and
 gamma-knife radiosurgery)
 and nonablative (nondestructive) (eg, microvascular
decompression (MVD)) interventions
Neurosurgical interventions

120.  The severity of pain associated with TN and its devastating
psychological effects  prompt diagnosis and
treatment essential.
 Without a proper understanding of its clinical features and
medical course  TN may go undiagnosed for years.
 With a proper diagnosis and early treatment, however,
 patients may achieve pain relief, and
 resume a healthy life.
TRIGEMINAL NEURALGIA

126.  GN ( vagoglossopharyngeal neuralgia) is less Common
 relatively less severe attacks
 The 2 disorders may occasionally co-exist.
 most common in females and patients over 50
 Most cases of GN are idiopathic,
 neurovascular compression may also be seen.
Glossopharyngeal Neuralgia

127.  GN is characterized by severe, transient, stabbing,
unilateral pain
 in the ear,
 tongue base,
 tonsillar fossa and/or
 beneath the angle of the jaw
CHARACTERISTICS

131.  include talking, yawning, coughing, and
Swallowing  may be severe enough to cause weight loss.
 also be triggered by touching the external auditory canal,
 the side of the neck,
 and the skin anterior to the ear
Common triggers

134.  GN may involve branches of the vagal nerve
 leading to bradycardia and syncope
 that may necessitate pacemaker placement
COMPLICATION

135.  Management of GN mirrors that of TN.
 Pharmacotherapy should be tried initially with the
preferred agents being the same as those used in TN
TREATMENT

140.  ON is a neuralgia with pathology related to cervical rather
than cranial nerves.
 The characteristic clinical presentation consists of
 brief, sharp shooting pain
 in the distribution of the occipital nerves,
 which is often associated with dysesthesia and allodynia
Occipital Neuralgia

147.  Nerve block with a local anesthetic
 and corticosteroid may provide temporary relief
 while a neuropathic pain medication (eg,
gabapentin) and physical therapy are initiated
TREATMENT

151.  pulsed radiofrequency ablation,
 occipital nerve stimulation,
 or a trial of BTX may be considered
REFRACTORY CASES

154.  PHN is the most common complication of
herpes zoster (also known as shingles),
 which results from reactivation of latent varicella
zoster virus
Postherpetic Neuralgia

158.  pain persisting more than 4 months after the
onset of rash in the area affected by herpes
zoster.
DEFINITION

161.  first line therapies for PHN include
 Carbamazepine
 tricyclic antidepressants (target=25–150 mg/d),
 Gabapentin (target=1800–3600 mg/d),
 pregabalin (target=150–600 mg/ d),
 topical lidocaine 5 % patch,
 Divalproex sodium 1000 mg per day
DRUG THERAPY

163.  In refractory cases or in patients intolerant of first
line agents,
 opioids and capsaicin may be considered.
 Combining the lidocaine patch with other agents has
also proven effective.
 Intravenous acyclovir for 2 weeks followed by
 oral valacyclovir ( latent ganglionitis is present and
may contribute to pain)
REFRACTORY CASES

171.  The neuralgias represent painful conditions of the head occurring
in a specific nerve dermatome.
 These disorders may be recognized by their characteristic clinical
presentations, including pain in a restricted topography.
 Although many cases are classical (primary), secondary etiologies
are not uncommon.
 Pharmacologic agents remain the first line treatment for many of
the neuralgias,
 but nerve blocks, surgery, and other procedures may be necessary
in refractory cases.
 Topical medications, in particular, may offer several advantages
CONCLUSION

176. THANK YOU...