Oxymorphone
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Oxymorphone (14-hydroxydihydromorphinone) is a semi-synthetic opioid of the morphinan class. It is derived from morphine but significantly more potent, with exceptionally high affinity for opioid receptors. It activates opioid receptors in the brain and spinal cord, suppressing pain signals and releasing dopamine in the brain's reward circuits.
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First synthesized in Germany in 1914,[1] oxymorphone entered US clinical use in 1959 as the injectable Numorphan and remained niche for decades. Oral tablets approved in 2006 were widely abused; a 2012 crush-resistant reformulation drove an injection epidemic that caused 181 HIV cases in rural Indiana — the largest rural HIV outbreak in US history.[2] The FDA requested withdrawal in 2017; generic extended-release forms remain available.[3]
Subjective effects include profound pain suppression, euphoria, heavy sedation, and emotional quieting. The experience centers on deep physical comfort — pain and anxiety dissolve into a warm, weighted calm that narrows awareness inward. Nausea, constipation, respiratory slowing, and a strong compulsive compulsive redosing urge are characteristic unwanted effects.
Oxymorphone produces rapid physical dependence, and the gap between a therapeutic dose and a fatal one is narrow.[4] Tolerance to pain relief builds faster than tolerance to respiratory suppression, so dose escalation steadily increases overdose risk — a danger that multiplies when combined with alcohol, benzodiazepines, or other opioids. Decades of clinical use provide a strong evidence base, though isolated oxymorphone-only fatality data remain sparse.
History[edit]
Discovery
Oxymorphone was first synthesized in Germany in 1914[1] as part of early semi-synthetic opioid research. It entered US clinical use in 1959 under the trade name Numorphan, available only in injectable and suppository form, and remained a niche analgesic for nearly five decades.
Clinical expansion
Oral formulations (Opana, Opana ER) were approved in 2006,[3] proving effective for postsurgical pain[5] and osteoarthritis.[6][7] After OxyContin was reformulated with abuse-deterrent properties in 2010, oxymorphone ER abuse rose sharply — surveillance documented a 2.91-fold relative risk increase.[8]
Public health crisis
A 2012 crush-resistant reformulation shifted abuse from snorting to injection.[9] Between 2014 and 2015, Scott County, Indiana recorded 181 confirmed HIV cases from injecting dissolved tablets — the largest rural HIV outbreak in US history.[2][10] Hepatitis C co-infection was found in 92.3% of those cases.[11]
Market withdrawal
In June 2017, an FDA advisory panel voted 18–8 that reformulated Opana ER's risks outweighed its benefits — the first time the FDA requested withdrawal of an opioid due to abuse-related public health consequences.[3] Endo Pharmaceuticals withdrew the product in July 2017; formal NDA withdrawal was published in December 2020.[12] Generic extended-release oxymorphone remains available in the United States as of 2026.
The name oxymorphone derives from its structural relationship to morphine: oxy- marks the 14-hydroxy and C-6 keto modifications, while -morphone truncates morphinone. The trade name Numorphan compressed "new morphine structural analog"; Opana, the 2006 oral brand, became more widely recognized during the opioid crisis.
Chemistry[edit]
Structural class
Oxymorphone belongs to the morphinan class — a family of pentacyclic compounds derived from the opium poppy alkaloid thebaine. Its systematic name, 14-hydroxydihydromorphinone, reflects the two structural changes from morphine: a hydroxyl group at carbon-14 and a ketone at carbon-6. The C-6 ketone is what gives oxymorphone its higher opioid receptor affinity and greater potency compared to morphine.[14] Molecular formula: C₁₇H₁₉NO₄.
Molecular properties
Oxycodone differs from oxymorphone by a single methoxy group; oxymorphone is in fact a metabolite of oxycodone, produced in the liver by CYP2D6 enzymes.[15] The molecule has four stereocenters — only the (−)-isomer is active at opioid receptors.[16] It is more lipid-soluble than morphine, allowing it to enter the brain rapidly after reaching the bloodstream.[17]
Pharmacology[edit]
Mechanism of action
Oxymorphone is a full agonist at mu opioid receptors, binding with exceptionally high affinity — among the strongest of any clinical opioid.[18] Receptor activation quiets pain signals at both spinal cord and brain level, and releases dopamine in the brain's reward circuits, producing euphoria.[19]
Pharmacological screening identifies oxymorphone as the most mu-selective clinical opioid tested, with no significant activity at other receptor types.[20] Its effects are driven almost entirely by a single receptor system.
Pharmacokinetics
Oral bioavailability is roughly 10% — the liver breaks down most of the drug before it reaches the bloodstream.[17] The half-life is 7 to 10 hours. Oxymorphone bypasses the CYP450 enzyme system used by nearly all other opioids,[21] which means fewer metabolic drug interactions than oxycodone, methadone, or fentanyl.
Neuroscience[edit]
Where it acts
Oxymorphone's pain-relieving effects begin in brainstem pathways that suppress pain signals before they reach conscious awareness, and directly at the spinal cord.[19] Its euphoric effects arise in the brain's reward circuit, where mu receptor activation releases a surge of dopamine. Because it acts almost exclusively through mu receptors,[20] the reward signal is unmodulated by the dysphoric effects seen in mixed-action opioids.
Why it matters
With chronic use, the drive to take the drug intensifies even as the pleasure it produces fades — craving outpaces satisfaction. Repeated mu receptor activation triggers compensatory brain changes: receptors become less responsive, and opposing pathways upregulate.[19] These adaptations are the biological basis of both tolerance and withdrawal.
Whether oxymorphone preferentially activates certain intracellular signaling pathways at the mu receptor remains unknown — an answer would clarify its respiratory depression and tolerance profiles. The active metabolite 6-OH-oxymorphone has never been characterized for receptor binding, leaving its contribution to overall effects uncertain.
Subjective Effects[edit]
Oxymorphone centers the experience on physical comfort. Pain and distress dissolve into a warm, enveloping calm — a heavy, quiet sensation that narrows awareness inward. The emotional insulation is defining: anxiety fades alongside physical sensation, and the mind settles into a slow, weighted drift.
Compared to oxycodone, oxymorphone produces comparable euphoria and drug liking at equivalent analgesic doses.[22] It produces a subjectively sharper onset and a higher ceiling of effects than morphine, owing to its greater lipid solubility.[17]
Effect Grid
Full therapeutic analgesia dominates the experience. Clear euphoria emerges as warm emotional satisfaction and bodily comfort. Pronounced sedation and anxiety suppression produce a state of deep physical and psychological ease. This is the standard clinical dose range (10–20 mg IR).
Constipation, nausea, and pupil constriction (miosis) are expected. A pervasive body high — warmth and tactile euphoria — settles across the body. Respiratory depression is present but typically subclinical at these doses in opioid-naive individuals without co-intoxicants.
Thought deceleration and cognitive impairment become noticeable — focus suppression and reduced information processing. Compulsive redosing urge may emerge. Duration is 4–6 hours. Ethanol co-ingestion increases peak concentration by 14–80% and must be avoided.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Vestibular distortion · Visual haze / noise · Visual processing suppression · Internal hallucinations
Sedation · Body high · Spontaneous body sensations · Bodily heaviness · Muscle relaxation · Tactile euphoria · Nausea · Physical fatigue · Sexual arousal suppression · Dizziness · Dry mouth · Tingling / electric sensations · Appetite suppression · Excessive sweating · Insomnia · Nasal congestion · Temperature dysregulation · Vomiting · Yawning · Nystagmus (eye wobbles) · Pain enhancement · Bodily dissociation
Bodily heaviness · Muscle relaxation · Tactile euphoria · Nausea · Physical fatigue · Sexual arousal suppression · Dizziness · Dry mouth · Tingling / electric sensations · Appetite suppression · Excessive sweating · Insomnia · Nasal congestion · Vomiting · Yawning · Nystagmus (eye wobbles) · Pain enhancement · Bodily dissociation
Analysis suppression · Focus suppression · Information processing suppression · Thought deceleration · Memory suppression · Motivation suppression · Aesthetic enhancement · Confusion · Language suppression · Memory fragmentation · Thought disorganization · Amnesia
Thought deceleration · Memory suppression · Motivation suppression · Aesthetic enhancement · Confusion · Language suppression · Memory fragmentation · Thought disorganization
Anxiety · Dysphoria · Empathy enhancement · Irritability
Social disconnection · Social connection · Trust enhancement · Sociability enhancement · Depersonalization · Derealization · Cognitive disconnection
Depersonalization · Derealization · Cognitive disconnection
Timeline
Initial warmth spreads through the trunk as subtle analgesia begins. Effects are faint — a quiet shift in baseline comfort rather than a clear drug onset.
Analgesia deepens noticeably. Euphoria emerges as warm emotional satisfaction. Sedation begins settling over the body.
Full analgesia, maximum euphoria, pronounced sedation, and cognitive slowing. Miosis is established. Body high is at its warmest and most enveloping.
Effects gradually diminish. Residual sedation and analgesia persist but euphoria fades. Nausea typically resolves.
Mild residual sedation and possible constipation. Baseline affect gradually returns. Subclinical impairment may persist well beyond subjective resolution due to the 7–10 hour elimination half-life.
Safety[edit]
- Acute toxicity
- High
- Chronic toxicity
- High
- Withdrawal
- Severe
- Tolerance buildup
- moderate
- Tolerance reset
- 28 days
- Physical
- High
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- High
- Cross-tol.
- morphine · oxycodone · hydromorphone
Toxicity
Acute toxicity
Oxymorphone has high acute toxicity with a narrow therapeutic index. Fatal overdose results from respiratory depression progressing to oxygen deprivation and cardiac arrest.[23]
Postmortem data document fatalities at blood concentrations as low as 0.13 mg/L in combination with other drugs.[4][24] No isolated oxymorphone-only fatalities with postmortem toxicology have been published. No human LD₅₀ has been established.safety citation needed
Respiratory depression
Oxymorphone suppresses breathing by activating mu receptors in brainstem respiratory centers.[23] At clinical intravenous doses, breathing volume drops by roughly 40%.[25] Cannabis co-use additively worsens this effect.[25]
Thrombotic microangiopathy
Injecting dissolved crush-resistant Opana ER tablets causes blood vessel damage and kidney failure.[26][27][28] The cause is the polyethylene oxide (PEO) excipient added in 2012, not the oxymorphone itself.[29]
Symptoms include destruction of red blood cells, low platelet counts, acute kidney failure, and retinal detachments.[30] Kidney recovery is often incomplete.[26][31] This complication was a major factor in the FDA's 2017 withdrawal request.[3]
Chronic toxicity
No substance-specific chronic organ damage has been documented beyond the class effects of long-term opioid use: hormonal disruption, immune suppression, and increased pain sensitivity. Chronic toxicity is rated high based on the dependence and withdrawal profile inherent to potent mu opioid receptor agonists.
Psychological risks
The primary psychological risks are dependence-associated: compulsive drug-seeking, narrowing of daily life, and withdrawal-driven anxiety, low mood, and insomnia. At therapeutic doses, oxymorphone reduces attention, slows processing, and impairs decision-making.[22]
Oxymorphone does not produce psychosis or hallucinations at standard doses. At very high doses, confusion and delirium can occur as signs of severe central nervous system depression.
Tolerance & dependence
Tolerance
Effects diminish with repeated use, requiring dose escalation. Tolerance develops to analgesia, euphoria, and sedation; it develops more slowly to constipation and pupil constriction.[32] Cross-tolerance with all other mu opioid agonists is a class effect.[19]
Physical dependence
Physical dependence develops with repeated use. Withdrawal brings anxiety, muscle aches, sweating, diarrhea, nausea, vomiting, and insomnia. Based on the 7–10 hour half-life, onset is expected within 12–24 hours of the last dose, peaking at 36–72 hours and resolving over 5–10 days.citation needed
In rare cases, severe opioid withdrawal can cause muscle breakdown — contradicting the common assertion that opioid withdrawal is never life-threatening.[33]
Dependence liability
Oxymorphone has high dependence liability. At equianalgesic doses, it produces drug liking and euphoria comparable to oxycodone.[22] Post-reformulation surveillance documented a 2.91-fold relative risk increase in abuse.[8]
People who cannot convert oxycodone to oxymorphone via CYP2D6 are significantly underrepresented among opioid-dependent individuals, suggesting oxymorphone production contributes to oxycodone's own abuse liability.[34]
Drug interactions
The most dangerous interactions involve additive respiratory and central nervous system depression.
CNS depressant synergy
Alcohol, benzodiazepines, GHB/GBL, and other opioids produce additive to synergistic respiratory depression with oxymorphone. Alcohol increases peak blood levels by 14–80%[35] and independently suppresses breathing. Published fatalities have consistently involved co-intoxicants.[4][24]
Cannabis interaction
THC additively worsens oxymorphone-induced respiratory depression.[25]
Metabolic interactions
Oxymorphone does not inhibit or induce major CYP450 enzymes,[36][21] making it less susceptible to metabolic drug interactions than oxycodone, methadone, or fentanyl.
Serotonergic interactions
Oxymorphone has no significant SERT activity,[20] making serotonin syndrome risk lower than for tramadol, tapentadol, or meperidine.
Contraindications
Absolute contraindications from FDA-approved labeling[37]:
- Significant respiratory depression in unmonitored settings
- Acute or severe asthma in unmonitored settings
- Known or suspected gastrointestinal obstruction, including paralytic ileus
- Hypersensitivity to oxymorphone hydrochloride or any formulation component
Relative contraindications:
- Concurrent alcohol use — peak blood level increase of 14–80% plus additive respiratory depression[35]
- Concurrent benzodiazepine or CNS depressant use — additive respiratory depression; documented in fatal cases[4]
- Liver impairment — oxymorphone is metabolized in the liver; impaired function may increase exposurecitation needed
- Kidney impairment — reduced clearance of metabolites; dose adjustment likely requiredcitation needed
- History of substance use disorder — high abuse liability confirmed in human and surveillance data[22][8]
Harm Reduction[edit]
Forms & Identification
Oxymorphone is encountered as pharmaceutical tablets — immediate-release and extended-release formulations. The primary identification concern is confirming tablet identity. Counterfeit tablets containing fentanyl or fentanyl analogs circulate across opioid markets.
Fentanyl test strips can detect contamination in dissolved tablet material. Use them on any tablet of uncertain provenance.
Extended-release tablets with a crush-resistant polyethylene oxide matrix pose a specific, severe risk when injected: the excipient causes blood vessel damage and kidney failure independent of the opioid itself.[26] Identifying the specific formulation — brand, generic manufacturer, matrix type — matters in ways unique to this compound.
Guidelines
- Test any tablet of uncertain provenance with fentanyl test strips before use
- Start with the lowest available dose, especially with a new source or after any period of reduced use — tolerance drops rapidly during abstinence, and oxymorphone's low oral bioavailability (approximately 10%) means parenteral doses are dramatically more potent than oral doses
- Take oral doses on an empty stomach or with consistent food intake — food increases peak blood levels by approximately 38%[37]
- Do not consume alcohol before, during, or after use — alcohol increases oxymorphone blood levels by 14–80%[35] and independently suppresses breathing
- Never use alone — respiratory depression can progress without warning
- Keep naloxone accessible and ensure anyone present knows how to administer it
- Do not crush, break, or dissolve extended-release tablets — this defeats the controlled-release mechanism and delivers a potentially fatal bolus dose
Set & Setting
Oxymorphone should never be used alone. Respiratory depression can progress from slowed breathing to stopped breathing without warning. A sober observer who knows how to recognize overdose and administer naloxone is the single most important safeguard.
A calm, comfortable environment reduces the likelihood of anxiety-driven redosing.
Aftercare & integration. In the hours and days after use, mood may drop below baseline as the brain's reward system recalibrates. Adequate hydration, nutrition, and sleep support physical recovery. Constipation may persist for 24–48 hours after the last dose.
For people using oxymorphone for pain management, honest assessment of whether analgesic benefit justifies escalating dose requirements is a recurring decision point. If the dose needed for pain suppression is climbing steadily, consultation with a pain specialist about opioid rotation or multimodal pain strategies is warranted.
Recovery & Support
Oxymorphone dependence responds to the same evidence-based treatments as other opioid use disorders. Medication-assisted treatment with buprenorphine or methadone reduces mortality, suppresses withdrawal, and stabilizes daily functioning. Naltrexone is an option after complete detoxification.
Abrupt cessation after prolonged use produces withdrawal that, while rarely life-threatening, is intensely uncomfortable and a primary driver of relapse. Medically supervised tapering or transition to buprenorphine reduces withdrawal severity. Peer support programs including SMART Recovery and mutual aid groups provide ongoing structure. Anyone experiencing difficulty reducing or stopping use should seek professional support — opioid use disorder is a medical condition, not a moral failure.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency:
- Breathing becomes slow (fewer than 8 breaths per minute), shallow, or stops
- Lips, fingernails, or skin turn blue or gray
- Person is unresponsive to voice or sternal rub (knuckles pressed firmly on breastbone)
- Gurgling, choking, or snoring sounds in an unconscious person
Immediate steps:
- 1. Call emergency services immediately
- 2. Administer naloxone if available — intranasal (one spray in one nostril) or intramuscular injection; repeat after 2–3 minutes if no response
- 3. Place the person in the recovery position (on their side) to prevent choking
- 4. Begin rescue breathing if the person is not breathing: tilt head back, lift chin, give one breath every 5 seconds
- 5. Stay with the person — naloxone wears off in 30–90 minutes, and respiratory depression may return
- 6. Do NOT induce vomiting
What to tell the dispatcher: State that the person is not breathing or breathing very slowly, that an opioid is suspected, whether naloxone has been given, the approximate time of last use, and any other substances involved. Good Samaritan laws in many jurisdictions protect people who call for help during an overdose.
Reversal agent: Naloxone (Narcan) reverses opioid respiratory depression within 1–3 minutes. Because oxymorphone's half-life (7–10 hours) exceeds naloxone's duration of action (30–90 minutes), repeated doses or continuous monitoring may be necessary. Naloxone will precipitate withdrawal in opioid-dependent individuals — this is uncomfortable but not life-threatening.
Legal Status[edit]
Oxymorphone is controlled as a narcotic in every major jurisdiction, reflecting its high abuse potential and accepted medical use under prescription.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Schedule II (Controlled Substances Act) | High abuse potential with accepted medical use; prescription required. Brand Opana ER withdrawn July 2017; generic ER formulations remain available[1][3] |
| United Kingdom | Class A, Schedule 2 (Misuse of Drugs Act 1971) | Most restrictive classification for therapeutic controlled drugs; placed alongside morphine and diamorphine[38] |
| Australia | Schedule 8 (Controlled Drug) | Restricted to medical use with specific prescribing requirementscitation needed |
| Canada | Schedule I (CDSA — Narcotic) | Listed under the Controlled Drugs and Substances Actcitation needed |
| International | Schedule I (UN Single Convention on Narcotic Drugs, 1961) | Subject to international narcotics controlscitation needed |
The formal NDA withdrawal for Opana ER was published in the Federal Register in December 2020.[12] This was unprecedented — the first time the FDA requested withdrawal of an approved opioid due to abuse-related public health consequences rather than intrinsic safety defects of the active ingredient.
Legal status changes over time and varies by jurisdiction. The information here reflects available data as of 2026 and is not legal advice.
references
- [1]
- [2] ^abPeters PJ, Pontones P, Hoover KW, et al. (2016) HIV Infection Linked to Injection Use of Oxymorphone in Indiana, 2014-2015 — New England Journal of Medicine doi:10.1056/nejmoa1515195
- [3]
- [4] ^abcdVorce SP, Levine B, McDonough PC, Past MR (2010) An overdose death involving the insufflation of extended-release oxymorphone tablets. — Journal of analytical toxicology PMID:21819798
- [5] ^Gimbel J, Ahdieh H (2004) The efficacy and safety of oral immediate-release oxymorphone for postsurgical pain — Anesthesia and Analgesia doi:10.1213/01.ane.0000132548.91622.b3
- [6] ^Matsumoto AK, Babul N, Ahdieh H (2005) Oxymorphone extended-release tablets relieve moderate to severe pain and improve physical function in osteoarthritis: results of a randomized, double-blind, placebo- and active-controlled phase III trial — Pain Medicine PMID:16266356