Opioid Medications Compared
Opioids are a class of medications that bind to opioid receptors in the brain, spinal cord, and peripheral tissues to reduce the perception of pain. They include naturally derived compounds (morphine, codeine), semi-synthetic derivatives (oxycodone, hydrocodone, oxymorphone, hydromorphone, buprenorphine), fully synthetic agents (fentanyl, methadone, tramadol), and are used for acute and chronic pain management, surgical anesthesia, cough suppression, and treatment of opioid use disorder (OUD). This guide covers all major opioids approved in the United States, organized by route of administration.
Opioid overdose is a medical emergency. Signs include unconsciousness or inability to wake, slow or stopped breathing, choking or gurgling sounds, limp body, pale or blue skin (especially lips and fingertips), and pinpoint pupils. If you suspect an overdose, call 911 immediately.
Naloxone (Narcan, Kloxxado, RiVive) is a life-saving medication that rapidly reverses opioid overdose. It is available without a prescription at most pharmacies in the United States. Naloxone nasal spray (Narcan 4mg, Kloxxado 8mg) is easy to administer and can be used by bystanders. Everyone who lives with or cares for someone taking opioids should have naloxone on hand and know how to use it.
SAMHSA National Helpline (free, confidential, 24/7): 1-800-662-4357
⚠ This page is for educational purposes only. All opioids listed are controlled substances requiring a prescription. This page does not provide dosing guidance. Never start, stop, or adjust an opioid without direct guidance from a licensed prescriber.
Quick Reference: All Major Opioids
| Brand Name | Generic | DEA Schedule | Duration of Action | Dosage Forms | Notable Features / Use |
|---|---|---|---|---|---|
| MS Contin / MSIR | Morphine | Schedule II | IR: 4–6 hr · ER: 8–24 hr | IR tablet, ER tablet, solution, injectable | Reference opioid; gold standard for comparison |
| Kadian | Morphine sulfate ER | Schedule II | 12–24 hr | ER capsule | Sprinkle capsule for feeding-tube administration |
| OxyContin / Roxicodone | Oxycodone | Schedule II | IR: 4–6 hr · ER: 12 hr | IR tablet, ER tablet | High abuse history; OxyContin reformulated 2010 |
| Percocet | Oxycodone / Acetaminophen | Schedule II | 4–6 hr | Tablet | Combination product; acetaminophen limits total use |
| Vicodin / Norco | Hydrocodone / Acetaminophen | Schedule II | 4–6 hr | Tablet | Most prescribed opioid in the US (historically) |
| Zohydro ER / Hysingla ER | Hydrocodone ER | Schedule II | 12–24 hr | ER capsule / ER tablet | Hydrocodone-only ER; no acetaminophen ceiling |
| Opana / Opana ER | Oxymorphone | Schedule II | IR: 4–6 hr · ER: 12 hr | IR tablet, ER tablet, injectable | Opana ER withdrawn from market 2017 (FDA request) |
| Dilaudid / Exalgo | Hydromorphone | Schedule II | IR: 4–5 hr · ER: 24 hr | Tablet, liquid, injectable, ER tablet | ~5× more potent than morphine; widely used in hospitals |
| Duragesic | Fentanyl (transdermal) | Schedule II | 72 hr per patch | Transdermal patch | For opioid-tolerant patients only; absorbed through skin |
| Actiq / Fentora | Fentanyl (transmucosal) | Schedule II | 1–2 hr | Lozenge, buccal tablet, nasal spray | Breakthrough cancer pain only (REMS program) |
| Codeine (various) | Codeine | Schedule II (alone) / III–V (combo) | 4–6 hr | Tablet, syrup, injectable | Prodrug; must convert to morphine via CYP2D6 |
| Ultram / ConZip | Tramadol | Schedule IV | IR: 4–6 hr · ER: 24 hr | IR tablet, ER tablet/capsule | Atypical opioid; also inhibits serotonin/NE reuptake |
| Suboxone / Subutex | Buprenorphine (± naloxone) | Schedule III | 24–72 hr | Sublingual film/tablet, injectable, patch | Partial agonist; also used for OUD treatment |
| Methadose / Dolophine | Methadone | Schedule II | Pain: 4–8 hr · Half-life: 8–59 hr | Tablet, liquid, injectable | OUD maintenance; complex pharmacokinetics; QT risk |
1. Oral Tablets and Capsules
Oral opioids are the most common form for outpatient pain management. They are further divided into immediate-release (IR) formulations, which work quickly over a shorter duration, and extended-release (ER) formulations, which provide prolonged effect through special coating or matrix technology. ER formulations must never be crushed, chewed, or dissolved — doing so releases the full dose at once and can be fatal.
Immediate Release
Morphine is the archetypal opioid — the compound against which all other opioids are measured in equianalgesic comparisons. It is derived from the opium poppy and has been used medically since the early 19th century. Morphine acts primarily on mu-opioid receptors to produce analgesia. It is metabolized in the liver to active metabolites including morphine-6-glucuronide (M6G), which contributes to its analgesic effect, and morphine-3-glucuronide (M3G), which can cause neuroexcitatory effects. Caution is required in patients with renal impairment as active metabolites can accumulate.
Immediate-release morphine tablets are used for moderate-to-severe acute pain and for breakthrough pain in patients on extended-release opioid therapy.
Oxycodone is a semi-synthetic opioid derived from thebaine, another alkaloid of the opium poppy. It is approximately 1.5 times more potent than morphine milligram-for-milligram. Oxycodone IR tablets provide short-term relief of moderate-to-severe pain. Oxycodone is metabolized primarily by CYP3A4 and CYP2D6 in the liver to oxymorphone (active) and noroxycodone (less active). Drug interactions involving CYP3A4 inhibitors or inducers can significantly alter oxycodone blood levels.
Oxycodone IR is also available combined with acetaminophen (Percocet) or aspirin (Percodan). The combination products carry an additional ceiling due to the non-opioid component.
Hydrocodone combined with acetaminophen was historically the most prescribed opioid in the United States. Hydrocodone is a semi-synthetic opioid derived from codeine; it is a prodrug that requires conversion to hydromorphone via CYP2D6 for a portion of its analgesic effect. The acetaminophen component provides additive analgesia but imposes a ceiling — cumulative acetaminophen from all sources (including OTC products such as Tylenol) must not exceed FDA-recommended daily limits, particularly in patients with liver disease or heavy alcohol use.
In 2014, the DEA rescheduled hydrocodone combination products from Schedule III to Schedule II, reflecting the high rates of misuse and diversion that had been documented with the older, less-restricted scheduling.
Hydromorphone is a semi-synthetic opioid derived from morphine, approximately 5 times more potent than morphine. It is commonly used in hospital settings for acute pain management due to its reliable potency and available injectable form. Oral Dilaudid tablets are used for moderate-to-severe pain. Hydromorphone has a more favorable metabolite profile than morphine in patients with renal impairment — its primary metabolite hydromorphone-3-glucuronide (H3G) can still accumulate but to a lesser extent than morphine metabolites in some patients, making it a preferred option in certain clinical situations.
Codeine is a naturally occurring opium alkaloid and the prototypical weak opioid. It is a prodrug that must be converted to morphine by the liver enzyme CYP2D6 to produce its primary analgesic and euphoric effects. This conversion varies dramatically by genetic CYP2D6 status: poor metabolizers (~7–10% of the population) receive little to no analgesic effect, while ultra-rapid metabolizers can convert codeine to morphine so quickly that they are at risk of overdose even at normal doses. The FDA has contraindicated codeine in children under 12 and in post-operative pain management in children due to deaths in ultra-rapid metabolizers.
Codeine is also used as a cough suppressant and is found in many combination cough-and-cold preparations. Combination products with codeine at low doses (≤90 mg per dosage unit with other active ingredients) may be Schedule III or V depending on the product and state law.
Tramadol is a centrally acting analgesic with a dual mechanism of action that distinguishes it from classical opioids. It binds to opioid receptors (primarily mu receptors) and also inhibits the reuptake of serotonin and norepinephrine, mechanisms shared with antidepressants. This dual mechanism means tramadol carries unique risks not typical of other opioids: it can lower the seizure threshold (particularly at higher doses or when combined with other serotonergic agents) and can cause serotonin syndrome when combined with SSRIs, SNRIs, MAOIs, or other serotonergic drugs. The opioid component still carries risk of dependence, respiratory depression, and abuse.
Tramadol is classified as Schedule IV by the DEA — considered to have lower abuse potential than Schedule II–III opioids, though dependence does occur. It is available in immediate-release and extended-release formulations.
Oxymorphone is a semi-synthetic opioid approximately twice as potent as oxycodone and 3 times more potent than morphine on a milligram basis. In 2017, the FDA requested that Endo Pharmaceuticals withdraw Opana ER (the extended-release formulation) from the market due to its association with a significant increase in injection drug use and an HIV outbreak in Indiana among people who injected the crushed tablets. The immediate-release formulation and generic versions have remained available but use has declined substantially. Oxymorphone IR is prescribed for moderate-to-severe acute pain.
Buprenorphine is a partial agonist at the mu-opioid receptor and an antagonist at the kappa-opioid receptor. Its partial agonist activity means it produces opioid effects up to a ceiling level — after which increasing the dose produces no additional effect, which provides a built-in safety margin against respiratory depression compared to full agonists. Suboxone (buprenorphine/naloxone) sublingual film and Zubsolv (sublingual tablets) are FDA-approved for the treatment of opioid use disorder (OUD) as part of a comprehensive treatment program including counseling.
The naloxone component is added to deter injection — naloxone is poorly absorbed sublingually but becomes fully active if the product is injected, precipitating immediate withdrawal in opioid-dependent individuals. Buprenorphine alone (Subutex) sublingual tablets are approved for situations where naloxone is not appropriate (e.g., pregnancy).
Methadone is a synthetic full opioid agonist with uniquely complex pharmacokinetics. It has an exceptionally long and highly variable half-life of 8–59 hours, which means it can accumulate in the body over days of use and cause delayed overdose — even after a patient feels the pain-relieving effect has worn off. This makes methadone particularly dangerous to initiate and titrate, and it should only be managed by clinicians experienced with its use. Methadone also blocks NMDA receptors, which may contribute to its efficacy in neuropathic pain.
Methadone is used for two distinct purposes: chronic pain management (prescribed through any DEA-registered provider) and opioid use disorder maintenance treatment (which in the US must be dispensed through federally regulated opioid treatment programs — methadone clinics — that are required to supervise ingestion, especially during induction). Methadone prolongs the QT interval and can cause life-threatening cardiac arrhythmias; an ECG is recommended before and during treatment.
Extended Release
⚠ Extended-release opioid tablets and capsules must NEVER be crushed, broken, chewed, or dissolved. Doing so defeats the controlled-release mechanism and delivers the entire dose at once, which can cause fatal respiratory depression. ER opioids are intended for opioid-tolerant patients requiring around-the-clock pain management — not for acute or as-needed use.
MS Contin was one of the first extended-release opioid formulations approved in the United States (1984). It uses a wax-matrix tablet technology that releases morphine slowly over 8–12 hours, allowing twice-daily dosing for around-the-clock pain management. Kadian, another morphine ER product, uses pellet-filled capsules that can be sprinkled on food or administered via feeding tube, and provides 12–24 hour coverage.
OxyContin is a 12-hour extended-release oxycodone formulation first approved in 1995. Its aggressive marketing and rapid prescription growth played a central role in triggering the opioid epidemic in the United States. In 2010, Purdue Pharma reformulated OxyContin with abuse-deterrent technology: the new tablet is harder to crush and forms a gel when dissolved, making it more difficult to misuse by snorting or injection. However, this reformulation drove many users toward illicitly manufactured opioids including heroin and fentanyl.
OxyContin is indicated for the management of severe pain requiring around-the-clock, long-term treatment in opioid-tolerant patients — it is not indicated for as-needed pain relief.
Exalgo is a once-daily extended-release hydromorphone tablet approved for opioid-tolerant patients requiring around-the-clock pain management. It uses an osmotic push-pull delivery system (OROS technology) to provide steady release of hydromorphone over 24 hours. Because it uses the same OROS system as some other ER medications, the tablet shell may be visible in a patient's stool — this is normal and does not mean the medication was not absorbed. Exalgo is only for opioid-tolerant patients and carries an enhanced risk of fatal overdose in opioid-naïve individuals.
2. Transdermal Patches
Transdermal opioid patches deliver medication through the skin into the bloodstream, bypassing the gastrointestinal tract. They are useful for patients who cannot swallow pills reliably, who have GI absorption problems, or who need stable around-the-clock analgesia without frequent dosing. Transdermal systems have specific storage and disposal requirements — used patches still contain significant amounts of active drug and must be disposed of safely to prevent accidental exposure, especially to children and pets.
The Duragesic patch delivers fentanyl continuously through the skin over 72 hours (3 days). Fentanyl is highly lipophilic, which makes it well-suited for transdermal delivery. A reservoir of fentanyl builds up in subcutaneous fat and skin layers after application, creating a slow and steady release profile. Due to this depot effect, it takes 12–24 hours after initial application to reach effective blood levels, and fentanyl continues to be absorbed for 12–24 hours after a patch is removed.
The fentanyl patch is indicated ONLY for opioid-tolerant patients. This is defined as patients who have been taking at least 60 mg oral morphine daily, 25 mcg/hr transdermal fentanyl, 30 mg oral oxycodone daily, 8 mg oral hydromorphone daily, or an equianalgesic dose of another opioid for a week or longer. Use in opioid-naïve patients carries an extreme risk of fatal respiratory depression.
Heat increases fentanyl absorption — patients must avoid heating pads, electric blankets, hot tubs, and sunbathing while wearing a patch, and must avoid situations causing fever, as significantly elevated absorption can occur.
Butrans delivers buprenorphine transdermally for the management of severe chronic pain requiring around-the-clock opioid analgesia. As a partial mu-opioid agonist, buprenorphine has a ceiling effect on respiratory depression that provides a relatively wider safety margin compared to full agonist transdermal opioids like fentanyl. Butrans is changed weekly (every 7 days), compared to fentanyl patches which are changed every 3 days. It is not indicated for opioid use disorder treatment — that use requires the sublingual formulations.
Like the fentanyl patch, Butrans absorption increases with heat. Application site rotation is required to reduce local reactions.
Illicitly manufactured fentanyl (IMF) is the primary driver of overdose deaths in the United States. Counterfeit pills pressed to look like oxycodone (M30 "blues"), Xanax (bars), Adderall, and other commonly used medications are routinely found to contain fentanyl or carfentanil — a fentanyl analogue approximately 100 times more potent than fentanyl itself.
A lethal dose of fentanyl is approximately 2 milligrams — an amount smaller than a few grains of salt, invisible to the naked eye, and impossible to identify by looking at a pill. There is no safe "test dose" of a counterfeit pill.
The only safe opioid pill is one dispensed directly by a licensed pharmacist from a legitimate prescription. Any pill obtained outside of a licensed pharmacy — regardless of how it looks, who provided it, or where it came from — should be treated as potentially lethal.
Fentanyl test strips are available in many states and can detect fentanyl contamination in substances. They are a harm-reduction tool but do not guarantee safety. Naloxone (Narcan) should be carried by anyone at risk of opioid exposure and by those who live with or care for them. Multiple doses of naloxone may be required for fentanyl and carfentanil overdose.
If you or someone you know needs help with substance use: SAMHSA Helpline: 1-800-662-4357 (free, confidential, 24/7)
3. Lozenges, Buccal, and Nasal Formulations
Transmucosal fentanyl products deliver fentanyl through the mucous membranes of the mouth or nose, producing rapid onset of effect (minutes) compared to oral administration. All transmucosal immediate-release fentanyl (TIRF) products are approved only for breakthrough cancer pain in opioid-tolerant adults and are subject to a Risk Evaluation and Mitigation Strategy (REMS) program requiring special prescriber training and patient enrollment. They are not interchangeable with each other or with other opioids on a mcg-per-mcg basis.
Actiq is a fentanyl lozenge on a handle (sometimes called a "lollipop") that is rubbed along the inside of the cheek and gum to deliver fentanyl through the oral mucosa. It produces onset of analgesia within 5–15 minutes, making it suitable for breakthrough cancer pain — pain that breaks through a patient's regular around-the-clock opioid therapy. The product must be rubbed actively; simply sucking on it like candy is less effective and increases GI absorption. Actiq is approved only for breakthrough cancer pain in opioid-tolerant patients and is subject to the TIRF REMS program.
Fentora is a buccal tablet containing fentanyl that is placed between the cheek and gum. It uses OraVescent technology — an effervescent reaction when the tablet contacts saliva that transiently changes local pH and enhances fentanyl absorption through the buccal mucosa. Fentora is not equivalent in dose to Actiq — 200 mcg Fentora is not the same as 200 mcg Actiq, and patients switched between products must be individually re-titrated. Like all TIRF medications, it is approved only for breakthrough cancer pain in opioid-tolerant patients enrolled in the REMS program.
Lazanda is a fentanyl nasal spray that delivers fentanyl through the nasal mucosa, producing rapid onset for breakthrough cancer pain. Subsys was a fentanyl sublingual spray; it was withdrawn from the US market by its manufacturer following federal criminal convictions related to illegal marketing practices and bribery of physicians. Lazanda remains available through the TIRF REMS program for opioid-tolerant cancer patients with breakthrough pain. Nasal absorption can be reduced by nasal congestion, rhinitis, or nasal polyps.
4. Injectable Opioids
Injectable opioids are used primarily in hospital, surgical, and hospice settings where rapid and precise pain control is needed, where patients cannot take oral medications, or where intravenous patient-controlled analgesia (IV-PCA) is appropriate. Intravenous administration produces the fastest onset and highest peak effect of any route, with a corresponding increase in risk of respiratory depression. Injectable opioids are almost exclusively administered by healthcare professionals in monitored settings.
Injectable morphine is a cornerstone of hospital pain management and is available in various concentrations for IV, IM, and subcutaneous administration, as well as for epidural and intrathecal use. IV morphine has an onset of action within 5 minutes and is commonly used in PCA pumps, which allow patients to self-administer small bolus doses within programmed safety limits. Morphine causes histamine release more than most other opioids, which can manifest as flushing, itching, and occasionally hypotension, particularly with rapid IV administration.
Injectable fentanyl is one of the most widely used opioids in anesthesia and procedural sedation. It is approximately 100 times more potent than morphine by weight (measured in micrograms, not milligrams). IV fentanyl has an extremely rapid onset of 1–2 minutes and a short duration of action of 30–60 minutes, making it highly controllable in procedural and surgical settings. It is also used in continuous infusion for ICU sedation and analgesia. Unlike morphine, fentanyl does not cause significant histamine release, making it preferable in patients with reactive airways or hemodynamic instability. Fentanyl is also used in neuraxial (epidural/intrathecal) analgesia during labor and surgery.
Injectable hydromorphone is used for moderate-to-severe acute pain in hospital settings and is also used in PCA pumps. It is approximately 5–7 times more potent than morphine on a milligram basis. Hydromorphone is often preferred over morphine in patients with renal impairment or who experience excessive sedation or pruritus from morphine. It is also commonly used in palliative care for severe pain and dyspnea. Hydromorphone HP (high potency) formulations are available in concentrated forms for subcutaneous infusion in palliative settings where large volumes are impractical.
Buprenex is an injectable formulation of buprenorphine used for moderate-to-severe pain in hospital settings. Sublocade is a once-monthly extended-release subcutaneous injection of buprenorphine used for the treatment of moderate-to-severe opioid use disorder in patients who have initiated treatment with a transmucosal buprenorphine product. Sublocade forms a solid depot under the skin that slowly releases buprenorphine over the month, which can improve treatment adherence by eliminating the need for daily sublingual administration and reducing the risk of diversion.
How Opioids Work
Opioids produce their effects by binding to opioid receptors — proteins embedded in the membranes of neurons. There are three main opioid receptor types, each producing different effects:
- Mu (μ) receptors: The primary target for analgesia and also the receptor responsible for euphoria, respiratory depression, constipation, and physical dependence. Most clinically used opioids work primarily at mu receptors.
- Kappa (κ) receptors: Contribute to analgesia but also cause sedation and dysphoria. Buprenorphine is a kappa antagonist, which may contribute to its antidepressant-like properties.
- Delta (δ) receptors: Play a role in mood and may modulate mu receptor activity. Less targeted by currently approved medications.
Opioids are classified by their pharmacological action at these receptors:
- Full agonists (morphine, oxycodone, fentanyl, hydrocodone, hydromorphone, codeine, methadone): Bind to and fully activate opioid receptors. Greater binding produces proportionally greater effect — including greater respiratory depression. No ceiling effect on analgesia or toxicity.
- Partial agonists (buprenorphine): Bind to opioid receptors but produce less than maximal activation. Ceiling effect limits respiratory depression risk, contributing to a wider safety margin. Can precipitate withdrawal in patients fully dependent on a full agonist.
- Mixed agonist-antagonists (nalbuphine, butorphanol): Activate some receptor types while blocking others. Limited use in clinical practice.
DEA Controlled Substance Schedules for Opioids
All opioids are federally controlled substances under the DEA. The schedule reflects the drug's accepted medical use combined with its abuse potential and dependence liability:
- Schedule II: High potential for abuse; accepted medical use; abuse may lead to severe psychological or physical dependence. Includes most strong opioids: morphine, oxycodone, hydrocodone, fentanyl, hydromorphone, oxymorphone, methadone, codeine alone. Schedule II requires a written prescription (electronic in most states); no refills are permitted; quantity limits may apply.
- Schedule III: Moderate potential for abuse relative to Schedule II; accepted medical use; abuse may lead to moderate or low physical dependence or high psychological dependence. Includes buprenorphine products (Suboxone, Subutex, Butrans) and low-dose codeine combinations in some states.
- Schedule IV: Lower potential for abuse; accepted medical use; limited physical or psychological dependence. Includes tramadol.
- Schedule V: Lowest potential for abuse; accepted medical use; limited dependence potential. Includes certain low-dose codeine cough syrups.
Opioid Equianalgesic Equivalency (Reference Only)
Equianalgesic tables are clinical reference tools used by healthcare professionals when converting a patient from one opioid to another. They express approximate equivalencies in terms of pain-relieving effect, typically referenced to 10 mg IV morphine or 30 mg oral morphine. These are approximate guides only — individual responses to opioids vary significantly based on genetics, tolerance, prior opioid exposure, organ function, and concurrent medications. Equianalgesic conversions must always be performed by a trained clinician, with appropriate reductions for incomplete cross-tolerance, and the result verified clinically.
⚠ The table below is for educational reference only and is NOT a dosing tool. Opioid conversions require clinical expertise and individualized patient assessment. Errors in opioid conversion can be fatal.
| Opioid | Approximate IV/IM Equivalence | Approximate Oral Equivalence | Notes |
|---|---|---|---|
| Morphine | 10 mg | 30 mg | Reference standard |
| Oxycodone | — | 20 mg (oral) | ~1.5× oral morphine potency |
| Hydromorphone | 1.5 mg | 7.5 mg | ~5× more potent than morphine |
| Hydrocodone | — | 30 mg (oral) | Roughly equianalgesic to oral morphine |
| Oxymorphone | 1 mg | 10 mg | ~3× more potent than oral morphine |
| Fentanyl (IV) | 0.1 mg (100 mcg) | N/A | ~100× more potent than IV morphine by weight |
| Codeine | 130 mg | 200 mg | Weak opioid; variable conversion via CYP2D6 |
| Tramadol | — | ~300 mg (rough equiv.) | Dual mechanism; conversion is approximate |
| Methadone | Highly variable — DO NOT use standard equianalgesic tables; consult a specialist | ||
| Buprenorphine | Partial agonist — standard equivalency tables do not apply in the same way | ||
Common Side Effects and Risks
All opioids share a class-wide side effect profile due to their common mechanism at opioid receptors:
- Respiratory depression: The most dangerous side effect, and the primary mechanism of opioid overdose death. Opioids slow the brain's drive to breathe. Risk is increased with concurrent CNS depressants (benzodiazepines, alcohol, muscle relaxants, sleep aids, gabapentinoids), in opioid-naïve patients, and at higher doses.
- Constipation: Opioid-induced constipation (OIC) affects the majority of patients. Unlike most other opioid side effects, tolerance to constipation develops slowly if at all. Peripherally acting mu-opioid receptor antagonists (PAMORAs) such as methylnaltrexone and naloxegol are specifically approved to treat OIC.
- Nausea and vomiting: Common at initiation; often improves with continued use as tolerance develops.
- Sedation and cognitive impairment: Opioids affect alertness, reaction time, and cognitive performance. Patients must not drive or operate heavy machinery until they understand how a medication affects them.
- Physical dependence: Occurs with regular opioid use. Abrupt discontinuation causes withdrawal — not the same as addiction. Tapering prevents withdrawal.
- Hormonal effects: Chronic opioid use can suppress testosterone and estrogen, causing hypogonadism, sexual dysfunction, and decreased bone density (opioid-induced androgen deficiency, OPIAD).
- Pruritus (itching): More common with morphine and other opioids that release histamine; less common with fentanyl and hydromorphone.
- Urinary retention: More common in men and with neuraxial opioid administration.
The combination of opioids with benzodiazepines, other CNS depressants, or alcohol greatly multiplies the risk of fatal respiratory depression. The FDA has placed a Boxed Warning on all opioids requiring prescribers to weigh this risk carefully and limit co-prescribing whenever possible.
Opioids Used in Opioid Use Disorder Treatment
Three medications are FDA-approved for the treatment of opioid use disorder (OUD) — a chronic, relapsing medical condition characterized by compulsive opioid use despite harmful consequences:
- Buprenorphine (Suboxone, Subutex, Sublocade): Partial mu-agonist. Can be prescribed by qualified physicians, nurse practitioners, and physician assistants from office-based settings (following SAMHSA regulations). Reduces cravings and withdrawal; ceiling on respiratory depression makes it safer than full agonists in overdose.
- Methadone: Full mu-agonist. For OUD, methadone can only be dispensed through federally licensed Opioid Treatment Programs (OTPs — commonly called methadone clinics). Highly effective when taken consistently; complex pharmacokinetics and QT prolongation risk require careful medical oversight.
- Naltrexone (Vivitrol): A full opioid antagonist — it is not itself an opioid. It blocks opioid receptors entirely, preventing any opioid from producing effect. Must not be initiated until the patient has been completely opioid-free for 7–10 days (or precipitated withdrawal is severe). Available as oral tablets or a once-monthly injectable (Vivitrol).
Medications for opioid use disorder (MOUD) are evidence-based treatments that reduce overdose deaths, decrease illicit opioid use, and improve quality of life. They are not "trading one addiction for another" — they are effective medical treatments recognized by SAMHSA, NIDA, and all major medical organizations.
Frequently Asked Questions
What is the difference between immediate-release and extended-release opioids?
Immediate-release (IR) opioids reach peak effect more quickly and have a shorter duration of action, typically 4–6 hours. Extended-release (ER) formulations use special coatings or matrix technology to release the drug slowly over 8–24 hours, providing more stable blood levels for around-the-clock pain management. ER opioids are intended for opioid-tolerant patients with chronic pain — not for as-needed use. They must never be crushed, chewed, or dissolved, as doing so releases the entire dose at once and can cause fatal overdose.
What DEA schedule are most opioids?
Most strong opioids — including oxycodone, morphine, hydromorphone, fentanyl, oxymorphone, and methadone — are DEA Schedule II, the highest restriction for medications with accepted medical use. Hydrocodone combination products (such as Norco) were rescheduled from III to II in 2014. Buprenorphine products used for opioid use disorder (such as Suboxone) are Schedule III. Tramadol is Schedule IV. Codeine-only preparations are Schedule II, but combination products with low-dose codeine may be Schedule III or V.
What is buprenorphine used for?
Buprenorphine has two primary medical uses. As Suboxone (buprenorphine/naloxone film or tablet) or Subutex (buprenorphine alone), it is used to treat opioid use disorder — reducing cravings and withdrawal symptoms as part of a comprehensive treatment program. As Buprenex (injectable) or Butrans (transdermal patch), it is used to treat moderate-to-severe chronic pain. The partial agonist mechanism produces a ceiling on respiratory depression, providing a wider safety margin compared to full opioid agonists.
Is tramadol a true opioid?
Tramadol is classified as an atypical opioid. It does bind to opioid receptors but also inhibits the reuptake of serotonin and norepinephrine — mechanisms shared with antidepressants. Its DEA Schedule IV classification reflects a lower but still real abuse and dependence potential. Despite being considered "milder" than Schedule II opioids, tramadol carries serious unique risks including seizures and serotonin syndrome that classic opioids do not share.
What is the counterfeit fentanyl risk?
Illicitly manufactured fentanyl (IMF) is the leading cause of drug overdose deaths in the United States. Counterfeit pills made to resemble oxycodone, Xanax, Adderall, and other medications routinely contain fentanyl or carfentanil — a fentanyl analogue roughly 100 times more potent than fentanyl. A lethal dose of fentanyl is approximately 2 milligrams, invisible to the eye. The only safe opioid pill is one dispensed by a licensed pharmacist from a legitimate prescription. Naloxone (Narcan) should be kept available by anyone at risk, and fentanyl test strips provide one layer of harm reduction.
What is naloxone (Narcan) and where can I get it?
Naloxone is a full opioid antagonist that rapidly reverses opioid overdose by displacing opioids from receptors. It is available without a prescription at most pharmacies in the United States. Narcan (naloxone 4 mg nasal spray) and Kloxxado (8 mg nasal spray) are the most common OTC formulations. Some states make naloxone available through public health programs at no cost. Multiple doses may be needed for fentanyl overdose. Naloxone wears off in 30–90 minutes — 911 must always be called in a suspected overdose even if naloxone appears to work.