Pain DDIs

Question 1

Opioids with TCAs or antihistamines

Answer 1

Worsen constipation or urinary retention

Question 2

Opioids plus MAOI

Answer 2

Shown with Demerol, Exalgo, Abstral, or Nucynta + MAOIs.
Syndrome: excitation, delirium, hyperpyrexia (fever), convulsions, severe respiratory depression
Opioids and MAOIs should be avoided within 14 days of MAOI.

Question 3

What opioids interact with 3A4 inhibitors?

Answer 3

Fentanyl and oxycodone - use with caution

Question 4

Which opioids activated by 2D6?

Answer 4

Codeine, hydrocodone, oxycodone
Slow metabolizers-little/no pain relief
Fast metabolizers-more frequent dosing

Question 5

What opioids metabolized by CYP450s?

Answer 5

codeine, hydrocodone, fentanyl, methadone, oxycodone

Question 6

Severe liver failure

Answer 6

Opioid effect could be increased, dose maybe adjusted

Question 7

Renal impairment: what drugs need adjustment?

Answer 7

Fentanyl, morphine: 25% for crcl 10-50, 50% <10

Question 8

Renal impairment and morphine

Answer 8

CL slowed, accumulation of active metab M6G so maybe adjust dose