Pharmacological Management of Post-Herpetic Neuralgia.pptx

1. Pharmacological Management
of Post-Herpetic Neuralgia
Presenter: Dr. Sujitha
Post Graduate, Pharmacology

2. Introduction
• Varicella zoster virus- causative agent of varicella &
herpes zoster
• Acute herpes zoster- self limiting
• Some patients experience pain from months to
years after resolution of rash (post herpetic
neuralgia- PHN)
• Incidence increase with impairment of immune
system
• More common in patients with cancer or HIV
infection

3. Definition

4. Risk factors:
• Older age
• Prodromal pain, severity of acute HZ
• Intensity of acute pain and ophthalmic involvement with keratitis
Clinical presentation:
• Malaise, headache, fever, or abnormal skin sensations (e.g., itching, burning, pain)
• Thoracic, cervical & trigeminal nerves- commonly affected
• Pain in herpes zoster- sharp or stabbing
• pain in PHN- burning sensation
• More than 90%- allodynia

5. Pathogenesis of pain

6. Pharmacologic Therapies for Postherpetic Neuralgia
1. Anticonvulsants
• Gabapentin, Pregabalin
• MOA- inhibit calcium-mediated neurotransmitter on α2δ-1 subunits decreasing density of pre
synaptic voltage-gated calcium channels & excitatory neurotransmitters
• 300 to 600 mg orally three times per day
• Adverse effects- Dizziness, sedation, somnolence, ataxia
2. Antidepressants
• Amitriptyline, Nortriptyline, Despiramine
• MOA- Block the active reuptake of norepinephrine and serotonin
• Adverse effects -Blurred vision, constipation, dry mouth, sedation, urinary retention

7. Pharmacologic Therapies for Postherpetic Neuralgia
3. Topical lidocaine
• Lidocaine patch- Up to three patches per day
• MOA- reduces firing of sodium channels on damaged pain fibers
• Adverse effects - Blisters, local erythema, rash
4. Topical capsaicin
• Capsaicin cream
• MOA- blocks C-fibre conduction & inactivates neuropeptide release from
peripheral nerve endings
• Adverse effects - Erythema, pain on application, rash

8. Pharmacologic Therapies for Postherpetic Neuralgia
5. Opioids
• Oxycodone, Morphine, Tramadol
• MOA- acts on mu, kappa & delta receptors coupled with inhibitory G-proteins causing closure of
voltage-gated calcium channels leading to potassium efflux, hyperpolarization & decreases production
of cyclic adenosine monophosphate- result in reduction of neuronal cell excitability & transmission of
nociceptive impulses
• Adverse effects- nausea, pruritus, drowsiness, constipation, dependence, addiction, sedation
6. Botulinum Toxin A
• MOA- acts by inhibiting release of pain mediators from nerve terminals and dorsal root ganglions,
reducing inflammation around nerve endings, deactivating sodium channels, and exhibiting axonal
transport
• Muscle weakness, fatigue, dry mouth, dizziness

9. Pharmacologic Therapies for Postherpetic Neuralgia
7. Nerve block
• stellate ganglion blocks, somatic blocks including epidural & paravertebral blocks
• Adverse effects- arachnoiditis, aseptic meningitis, headache, and urinary retention
8. Neuromodulation
• transcutaneous electrical nerve stimulation (TENS), peripheral nerve stimulation (PNS), Spinal
Cord Stimulation (SCS), and radiofrequency
• Adverse effects- thermal or nerve injuries
9. Vaccination
• Zostava -zoster vaccine
• Adverse effects- minor injection site reactions

10. Recent advances
• AT2R antagonist- Olodanrigan- Oral: 25, 100, 300 mg BID
• VGCC 2 subunit inhibitor- Crisugabalin- Oral: 4, 20 mg BID
• LANCL ligand- LAT8881- Oral: 30 mg BID
• NMDAR antagonist- Esketamine- Intranasal: 5–35 mg TID
• Mu opioid agonist and SNRI- Sustained-release tramadol- Oral: 100–400 mg/day
BID

11. Conclusions
• PHN- complicated and burdensome neuropathic pain, which influences the
individual's daily function and quality of life.
• Several agents and methods are available to provide relief from PHN symptoms
• Most widely used combination therapy, gabapentinoids with topical analgesics
• For patients with intractable pain even after conservative management, invasive
interventional techniques are applied
• Primary task is to administer appropriate pain-relieving measures for better
outcomes in patients. Early management increases the chances of complete pain
relief from PHN
• Vaccination- useful measure to prevent herpes zoster

12. References
• Goodman & Gilman’s The Pharmacological Basis Of Therapeutics. (13th Edition)
• Kaushik Lahiri Post Graduate Dermatology (Volume 2)
• Huerta, M.Á.; Garcia, M.M.; García-Parra, B.; Serrano-Afonso, A.; Paniagua, N. Investigational
Drugsfor the Treatment of Systematic Neuralgia: Review of Postherpetic Randomized
Controlled Trials. Int. J. Mol. Sci. 2023, 24, 12987.
• Shrestha M, Chen A. Modalities in managing postherpetic neuralgia. Korean J Pain. 2018
Oct;31(4):235-243. doi: 10.3344/kjp.2018.31.4.235. Epub 2018 Oct 1. PMID: 30310548; PMCID:
PMC6177534.
• Derry S, Wiffen PJ, Moore RA, Quinlan J. Topical lidocaine for neuropathic pain in adults.
Cochrane Database Syst Rev 2014: CD010958.
• Navez ML, Monella C, Bösl I, Sommer D, Delorme C. 5% lidocaine medicated plaster for the
treatment of postherpetic neuralgia: a review of the clinical safety and tolerability. Pain Ther
2015; 4: 1-15.