Pain management

Question 1

What is the dosage of carbamazepine and what kind of pain is it useful in treating?

Answer 1

Carbamazepine (Tegretol)

-most useful for treating neuralgic pain

100mg BID initial dose

200-400mg BID

SE: drowsiness, diziness, constipation, nausea, ataxia, increased LFT’s, many metabolic drug interactions

Question 2

What is the first and second line treatments for neuropathic pain?

Answer 2

1st line= TCA’s

amitryptiline (Elavil)- 10-25 mg HS initial to 10-100mg HS maintenance

(max 300)

Nortryptiline (aventyl)- 10mg HS initial to 20-50mg HS (max 150mg)

SE- prolonged QT, hypotension, BPH

SNRI’s

venlafaxine (effexor)- 37.5mg OD (75-150mg OD) max 300mg

duloxetine (cymbalta)-30mg OD (60mg OD) with max 120mg/day

Question 3

What is the opioid standard by which all other strength of opioids is measured?

Answer 3

Morphine

Question 4

What is the dosage of morphine in its different forms?

Answer 4

Morphine 10 mg q4h sc/IV/IM

Morphine PO (Statex) 20-30 mg q4h

(bioavailability PO is ~35%)

12 H Morphine SR= MS Contin, MOS-SR, M-Eslon= 20-30mg mg q4h PO

24H Morphine SR= Kadian 20-30mg q4h PO

Question 5

What would be the conversion of Morphine SR (M-eslon) PO q12 to continuous infusion IV?

Answer 5

Example: Change 90 mg q12 Extended Release Morphine to Morphine by IV continuous infusion

Calculate the 24 hour current dose: 90mg q 12 = 180 mg Morphine/24 hours

Use the oral to parenteral equianalgesic ratio: 30 mg PO Morphine = 10 mg IV Morphine

Calculate new dose using ratios: 180/30 x 10 = 60 mg IV Morphine/24 hours or 2.5 mg/hour infusion

Some experts recommend starting the new opioid at 75% of the calculated dose to account for inter-individual variation in first pass clearance.

Question 6

What is the typical conversion used between types of analgesia?

Answer 6

Morphine 10 mg parenteral = Morphine 30 mg oral

Morphine 1

Meperidine 10

Codeine 6.67

oxycodone 0.667

hydromorphone 0.2

Question 7

What should the typical breakthrough dose of morphine be?

Answer 7

10-20% of total daily dose

Question 8

What is the method of opioid conversion when you are changing drugs but not changing route or administration?

Answer 8

Calculate the 24 hour current dose: 90 Q12 x 2 = 180 mg PO Morphine/24 hrs

Use the equianalgesic ratio: 30 mg PO Morphine = 7.5 mg PO Hydromorphone

Calculate new dose using ratios: 180/30 X 7.5 = 45 mg oral Hydromorphone/24 hours.

Reduce dose 50% for cross-tolerance: 45 x 0.5 = 22 mg/24 hours = 4 mg q4h

Cross tolerance speaks to the idea that between types of opioids there can be incomplete tolerance of the new drug, and so it should be started at 50% of the dose of the old drug asuming good pain control with the old drug

Question 9

What are the diagnostic criteria for a migraine without aura headache?

Answer 9

A-at least 5 full attacks meeting criteria B and D

B-Headache lasts 4-72H

C-Headache has 2 of the following qualities

unilateral

moderate to severe

pulsating

agrivated by or causes avoidance of physical activity

D-During headache have at least of the following

N/V

photophobia/phonophobia

E-

Question 10

What are the diagnostic criteria for a migraine with aura?

Answer 10

A-2 full attacks meeting criteria B and D

B-One or more fully reversible aura symptoms

visual

sensory

speech/language

motor

brainstem

retinal

C-At least 2 of the following 4 characteristics

• at least one aura symptom spreads
• unilateral
• lasts 5-60 minutes
• the aura acompanied or followed by headache within 60 minutes

D-No better diagnosis and TIA has been excluded

Question 11

What are the criteria for a chronic migraine headache?

Answer 11

A-Migraine or tension type headache for > 15 days/month for > 3 months
+ fullfills B and C

B-occus in patient who has had at least 5 attacks with or without an aura (meets criteria for migraines)

C-on at least 8 days/ month had migraine that

• didn’t meet criteria for aura
• met criteria for aura
• was aborted

Question 12

What are the descriptors used for neuropathic pain?

Answer 12

**Allodynia **

Pain resulting from a non-noxious stimulus to normal skin, such as touch

**Causalgia (CRPS II) **

Burning pain due to traumatic injury of a peripheral nerve

**Hyperalgesia **

Abnormally painful response to a stimulus, especially a repetitive stimulus, as well as a decreased pain threshold

**Hyperpathia **

Abnormally exaggerated subjective response to painful stimuli