Maois
Contraindicated
Database
Severe, potentially fatal serotonergic/cardiovascular reaction
Avoid within 14 days of an MAOI
Source: Kimi deep-research + Cla
Drug reference
Fentanyl
Potent synthetic opioid (phenylpiperidine, mu-agonist) · Analgesic
Also known as Fentanyl Citrate, Duragesic, Sublimaze, Actiq, Fentora, Abstral
START
IV 25–100 mcg titrated (anaesthesia); transdermal only in opioid-tolerant — convert from prior opioid, 12–25 mcg/h
TYPICAL MAX
Titrate to effect/safety; transdermal by equianalgesic conversion (avoid in opioid-naïve)
STOP IF
Respiratory depression (naloxone, possibly repeated/infusion — long patch depot), chest-wall rigidity, ileus
WATCH
Respiratory rate/sedation, opioid-tolerance status, heat exposure with patches, CNS-depressant co-use; naloxone available
CDSCO approvedSchedule XATC N01AH01
KDIGO 2024 + manufacturer label
- ONSET
- 2min · IV onset (~2 min)
- PEAK
- 5min · IV peak (~5 min)
- t½
- 4h · IV plasma t½
- DURATION
- 45min · IV analgesia (single dose)
EXCRETION
Hepatic CYP3A4; renal inactive metabolites
route + CYP
INTERACTIONS
12 major
incl. contraindicated
PREGNANCY
Use only if clearly needed — neonatal opioid withdrawal/respiratory depression with prolonged or peripartum use
FDA category + note
Top interactionssee all 12 →
- MaoisContraindicatedDatabaseKimi deep-research + Cla
- AlmotriptanSevereDatabaseDDInter
- AlvimopanSevereDatabaseDDInter
- AminoglutethimideSevereDatabaseDDInter
Available in India
15 branded formulations. Look up specific brands in the Drugs workspace.
Mechanism
High-affinity mu-opioid receptor agonist producing rapid, potent analgesia and sedation; highly lipophilic (fast CNS entry); ~100× morphine potency; minimal histamine release.
Indications
Severe acute/peri-operative pain and anaesthesia (IV)Procedural sedation/analgesiaChronic severe (often cancer) pain in opioid-tolerant patients (transdermal/transmucosal)Breakthrough cancer pain (transmucosal — opioid-tolerant only)
Dosing
- Adult
- IV: 25–100 mcg titrated (anaesthesia higher). Transdermal: 12–25 mcg/h start in opioid-tolerant, change q72h, titrate by equianalgesic conversion. Transmucosal breakthrough: lowest dose, titrate (opioid-tolerant).
- Pediatric
- IV 1–2 mcg/kg titrated (specialist).
- Renal adjustment
- No active renal metabolites — relatively preferred in renal impairment; still titrate (reduced clearance in severe).
- Hepatic adjustment
- Reduce dose (hepatic metabolism; accumulation in cirrhosis).
- Geriatric
- Markedly reduce dose; heightened respiratory depression.
- Max dose
- Titrated to effect/safety; transdermal by equianalgesic conversion (no fixed ceiling in tolerance)
Pharmacokinetics
Onset
IV ~1–2 min; transdermal 12–24 h to effect
Peak effect
IV ~5 min; patch steady state 24–72 h
Duration
IV 30–60 min; patch ~72 h
Half-life
IV ~3–7 h; transdermal apparent ~17–25 h (depot)
Bioavailability
Transmucosal ~50%; transdermal ~92%
Protein binding
~80–85%
Metabolism
Hepatic CYP3A4 → inactive norfentanyl
Excretion
Renal (mostly inactive metabolites)
Contraindications
- Opioid-naïve patients for transdermal/transmucosal products
- Acute/severe respiratory depression; acute/severe asthma (unmonitored)
- Paralytic ileus / GI obstruction
- Concurrent or recent (14 days) MAOI
- Management of acute/postoperative/mild or intermittent pain with transdermal patch
Side effects
Common
Respiratory depression/sedationNausea/vomiting, constipationBradycardia, hypotensionPruritus, muscle rigidity (rapid IV)
Serious
- Fatal respiratory depression (esp. opioid-naïve, with CNS depressants, heat-accelerated patch absorption)
- Chest-wall rigidity (rapid high-dose IV)
- Dependence/addiction, withdrawal
- Serotonin syndrome (with serotonergics); adrenal insufficiency; QT effects (high dose)
Pregnancy & lactation
Pregnancy
Use only if clearly needed — neonatal opioid withdrawal/respiratory depression with prolonged or peripartum use
Lactation
Single peri-procedural dose acceptable; chronic use — monitor infant (sedation/apnoea)
Drug interactions
Almotriptan
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Alvimopan
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Aminoglutethimide
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Amitriptyline
Severe
Database
Drug interaction classified as: synergy.
Source: DDInter
Amobarbital
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Amoxapine
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Amprenavir
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Apalutamide
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Aprepitant
Severe
Database
Drug interaction classified as: metabolism.
Source: DDInter
Aripiprazole
Severe
Database
Drug interaction classified as: synergy.
Source: DDInter
Armodafinil
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Related guidelines
Ask House about Fentanyl
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e, Katzung, BNF·Verified: 2026-05-19 · House clinical team·Cockpit curated: 2026-05-19