[Verse 1]
Codeine rolls in thinking it's a player on the block
But CYP2D6 determines if it ever clocks
Poor metabolizers get a sugar pill effect
Ultra-rapid converters hit a toxic intercept
Ten percent of the population converts fast and mean
Morphine floods the system from the codeine in between
Neonates have died, nursing mothers didn't know
The FDA restriction came because the data said so
Genetic roulette table, every patient spinning fate
You prescribe the same milligrams, the outcome's never straight
[Chorus]
C-Y-P-2-D-6, it's the enzyme running tricks
Codeine needs conversion but the variation sticks
Renal failure, rotate right, check the metabolites
Five steps to a safe rotation, do the safety checks tonight
Fentanyl and methadone clear when kidneys quit the game
Morphine-six-glucuronide will stack and cause you pain
[Verse 2]
Kidney function fading, now you gotta shift your game
Morphine leaves a metabolite, M6G is its name
Accumulates in renal failure, respiratory hit
Hydromorphone's H3G builds neuroexcitatory grit
Meperidine breaks to normeperidine, that's the seizure seed
Avoid those three when creatinine clearance drops with speed
Fentanyl stays lipid-soluble, hepatic metabolism clear
Methadone conjugates the liver route, no renal fear
When the glomerulus gives out, your analgesic roster shifts
Fentanyl and methadone patch — those are the kidney gifts
[Chorus]
C-Y-P-2-D-6, it's the enzyme running tricks
Codeine needs conversion but the variation sticks
Renal failure, rotate right, check the metabolites
Five steps to a safe rotation, do the safety checks tonight
Fentanyl and methadone clear when kidneys quit the game
Morphine-six-glucuronide will stack and cause you pain
[Verse 3]
Opioid rotation — patient's tolerant but side effects are rough
Step one, calculate the equianalgesic dose, do the math that's tough
Step two, reduce by twenty-five to fifty percent
Incomplete cross-tolerance means the new drug hits different, evident
Step three, assess the patient — pain, sedation, vitals clean
Step four, divide the daily dose across a proper dosing scheme
Step five, write breakthrough orders, ten percent of total daily
Monitor the first twenty-four hours, reassess it daily
Never switch milligram to milligram like a lazy substitution
Incomplete cross-tolerance demands that dose reduction
[Bridge]
Equianalgesic tables are a compass, not a law
Methadone conversions shift with dose and need a closer draw
High-dose morphine-equivalent converts at a steeper rate
Consult palliative specialists before you estimate
Document the reason for rotation, note what failed before
Track the adverse effects you're escaping at the door