Fentanyl vs Hydromorphone
## Overview
Fentanyl and hydromorphone are both used for severe pain in hospital/palliative settings. Fentanyl's extreme lipophilicity enables transdermal delivery and rapid IV onset; hydromorphone's high water solubility enables concentrated SC infusions.
## Mechanism of Action
Both are full mu-opioid receptor agonists. Fentanyl's lipophilicity results in rapid CNS penetration but also rapid redistribution.
## Pharmacokinetics
Fentanyl: no active metabolites, CYP3A4 to norfentanyl; context-sensitive half-life important with prolonged IV infusion (can approach 12+ h after multi-day ICU infusion). Hydromorphone: H3G metabolite (neuroexcitatory), half-life 2–3 h (IV).
## Palliative Care Selection
For SC infusion: hydromorphone preferred (highest water solubility, concentrated solutions possible). For transdermal: fentanyl. For ESRD/CKD: fentanyl preferred (no active metabolites). For rapid IV bolus analgesia/sedation: fentanyl.
## Equianalgesic
IV fentanyl 100 mcg ≈ IV hydromorphone 1.5 mg.
## Key Takeaways
- Hydromorphone: high water solubility (SC infusion advantage), higher potency per mg vs. morphine
- Fentanyl: no active metabolites (preferred in CKD), transdermal availability, rapid IV onset
- Both suitable alternatives to morphine when it is not tolerated
Sonuç
Fentanyl is preferred for CKD/ESRD patients and transdermal chronic pain management. Hydromorphone is preferred for subcutaneous continuous infusion in palliative care. Both are appropriate alternatives to morphine for severe pain when morphine is not tolerated.