6 Pain Drugs

Question 1

partial mu-agonist, but more potent than morphine at low doses

Answer 1

buprenorphine

Question 2

methadone

-uses, half-life, inactivation, side-effects

Answer 2

strong u agonist but less respiratory and euphoric (safer)
management of opioid dependence
orally active, long (40 hours)
CYP2D6 and 3A4
QT prolongation
blocks NMDA and MAO
-neuropathic pain and hyperalgesia

Question 3

codeine

-uses, half-life, inactivation, side-effects

Answer 3

methyl-morphine
– weaker mu agonist than morphine, and less potent
– low risk of dependence
• clinical uses: analgesic, antitussive with paracetamol (at doses with no analgesic effect)
• pharmacokinetics:
– converted to morphine by CYP2D6 – potential risks in 2D6*2x2 individuals
• less prone to first-pass metabolism than morphine
– t1/2 ~2-4 hr – similar to morphine

Question 4

fentanyl

-uses, half-life, inactivation, side-effects

Answer 4

strong mu agonist
more potent than morphine
short (1-2 hours)
highly lipophilic
metabolized by CYP3A4
given by IV, transdermal, parenteral
high risk for abuse/OD/death

Question 5

How do you diagnose opioid poisoning in an addict?

Answer 5

pupil constrction is resistant to opioid tolerance

Question 6

What are two opioid antagonists?

Answer 6

naloxone, naltraxone

Question 7

Pethidine

Answer 7

“STRONG” mu agonist – but weaker & less potent than morphine
– also k agonist
-t1/2 = 2-4 hours
-lipophilic
-significant first pass (causes seizures)
-anti-muscarinic (confusion)
-cause MAO inhibits and SSRI, serotonin syndrome by blocking 5HT reuptake

Question 8

where in the CNS do opioid target?

Answer 8

PAG (midbrain), NRM (medulla), LC (pons), dorsal horn (spinal cord)

Question 9

tramadol

Answer 9

weak mu and low potency
inhibits MAO reuptake
6 hours half-life (3A4, 2D6)
seizures
interacts with MAOI and SSRI