Pain drug delivery

Question 1

Intraspinal drug delivery

- Used when pt have inadequate pain control or intolerable side effects

Answer 1

Intrathecal

• Administered into intrathecal space
• Directly into CSF

Epidural

• Administered into epidural space
• systemic

Question 2

Ziconotide (Prialt)

- Intrathecal use in severe chronic pain

Answer 2

• MOA: N-type Ca channel antagonist (binds N type Ca channel in primary nociceptive afferent nerves in dorsal horn; blocks excitatory NT release from primary afferent terminals)
• No effect on opioid receptors
• ADR: Dizziness, ataxia, somnolence, N
• WARNING: neuropsychiatric ADR, contraindicated in pts with h/o psychosis, monitor pts for cognitive impairment, hallucinations, mood change or change in consciousness

Question 3

Intrathecal Baclofen (Lioresal)
- For severe spasticity

Answer 3

• Recommend single dose to determine response prior to using implantable pump
• ADR: hypotonia, somnolence, dizziness

Question 4

Topicals

Answer 4

• Analgesics
• Anesthetics
• Counterirritants
• Antipruritic

Question 5

Topical Analgesics

• Methyl salicylate
• Trolamine salicylate

Answer 5

• Watch salicylates with anticoagulants
• Watch for aspirin allergy
• Short term use (no more than 1 week)

Question 6

Topical Counterirritants

• Menthol
• Camphor
• Capsaicin

Answer 6

• Used for minor myalgia/arthralgia
• Creates irritation/inflammation locally to relieve inflammation in underlying or adjacent tissues
• Antinociceptive effects due to activation of endogenous opioids
• Local anesthetic actions

Question 7

Group A

Answer 7

• MOA: rubefacients
• methyl salicylate
• apply no more than TID to QID for up to 7 days

Question 8

Group B

Answer 8

• MOA produce cooling sensation
• Camphor menthol
• same as group A

Question 9

Group C

Answer 9

• MOA: cause vasodilation
• histamine dihydrochloride, methyl nicotinate
• same as group A

Question 10

Group D

Answer 10

• MOA: incite irritation w/ rubefaction
• capsicum, capsicum oleoresin
• For acute pain dosing: same as group A
• For chronic pain dosing: apply TID to QID PRN (long term use should be under medical supervision)

Question 11

Menthol (Peppermint)

Answer 11

• Used orally for GI complaints: Antispasmodic for IBS, lower GI motility, relaxes LES
• Topically for pain, inflammation, pruritus (may directly inhibit pain receptors and alter pain perception)
• ORAL ADR: heartburn, N/V
• TOPICAL ADR: skin irritation, contact dermatitis

Question 12

Menthol rub abuse

Answer 12

• Used at raves to enhance high from XTC or MDMA

Question 13

Camphor

Answer 13

• Topical antitussive/analgesic
• Possibly effective for OA
• Very toxic orally (N/V, burning of mouth and throat initially– breath will have characteristic camphor odor)
• Can lead to seizure, respiratory failure

Question 14

Capsaicin (Zostrix, Qutenza)

• For post herpetic neuralgia (after shingles)
• Specifically indicated for topical: pain of shingles, OA, RA, post herpetic neuralgia, trigeminal neuralgia, diabetic neuropathy, back pain, post op, HIV associated neuropathy, fibromylagia (relieve muscle spasms, as a gargle for laryngitis, deterrent to thumb sucking or nail biting)

Answer 14

• TRPV 1 channel agonist: transient receptor potential vanilloid 1; Ion channel receptor complex attached to skin nociceptors; activated by heat and low pH
• MOA: initially enhances TRPV1 stimulation–>pain relief follows when TRPV1 nociceptors are reduced (desensitized)–> depletes substance P
• ORAL USE: dyspepsia, flatulence, colic, D, cramps, toothache, poor circulation
• INTRANASAL USE: allergic rhinitis, perennial rhinitis
• ORAL ADR: GI discomfort, sweating, flushing (anticoagulation)
• TOPICAL ADR: burning, stinging, erythema (worsening ACEI cough)
• ADR tend to improve with time

Question 15

Iontophoresis (Transdermal drug delivery)

Answer 15

• Uses ion current to deliver charged drugs through the skin
• Often dexamethasone phosphate to reduce inflammation (NSAIDs, local anesthetics, salicylates)
• Can be used in PT