What is M367 Pill?

The M367 pill is a white, oval-shaped prescription tablet containing 10 mg of hydrocodone bitartrate and 325 mg of acetaminophen, used to treat moderate to severe pain that cannot be managed by non-opioid medications alone. Hydrocodone is a Schedule II controlled opioid, and the M367 imprint identifies this specific dosage combination manufactured by Mallinckrodt Pharmaceuticals. It is one of the most widely prescribed and most widely misused opioid formulations in the United States.

The M367 pill is searched by people who have found a pill and need to identify it, by patients managing pain who want to understand what they are taking, and by family members who have discovered the pill in a loved one’s possession. This guide covers what M367 is, how it works, why it is dangerous, and what treatment looks like for people who have developed dependence or addiction.

Key Highlights

• The M367 pill contains 10 mg of hydrocodone and 325 mg of acetaminophen. It is a stronger formulation than the M365 pill, which contains only 5 mg of hydrocodone with the same acetaminophen dose.
• Hydrocodone is a Schedule II controlled substance under the Controlled Substances Act. The DEA classifies Schedule II drugs as having a high potential for abuse that may lead to severe psychological or physical dependence.
• The FDA reports that more than 136 people die every day from opioid-related overdoses in the United States, with prescription opioids including hydrocodone contributing significantly to that total.
• Acetaminophen toxicity from exceeding 4,000 mg per day is a serious and separate danger in M367 misuse. Liver failure from acetaminophen overdose can occur before opioid overdose symptoms become apparent.
• M367 addiction is opioid use disorder. It is treatable with medically supervised detox, medication-assisted treatment (MAT), and behavioral therapy.

What Is the M367 Pill? Identification and Composition

The M367 pill is identified by its white oval shape and the imprint “M367” stamped on one side. The “M” refers to Mallinckrodt Pharmaceuticals, the manufacturer. It is a brand-equivalent of Vicodin, Norco, and Lortab, which are trade-name versions of the same hydrocodone-acetaminophen combination at equivalent doses. All contain the same two active ingredients in the same amounts, differing only in manufacturer and physical appearance.

The two active ingredients serve distinct pharmacological roles. Hydrocodone is a semi-synthetic opioid derived from codeine that acts on mu-opioid receptors in the brain and spinal cord to block the perception of pain and produce euphoria. Acetaminophen is a non-opioid analgesic that reduces pain and fever through a separate central nervous system mechanism, enhancing hydrocodone’s pain-relieving effect without significantly increasing its side effect profile at therapeutic doses. According to a review published in StatPearls by the National Institutes of Health (2024), the combination demonstrates increased analgesic efficacy compared to either agent used alone.

M367 is prescribed for conditions including post-surgical pain, injury-related pain, chronic musculoskeletal pain, and cancer-related pain that has not responded to non-opioid treatment. It is an immediate-release formulation, meaning its effects begin within 30 to 60 minutes and last approximately 4 to 6 hours per dose.

M367 vs. Similar Hydrocodone Pills

Understanding the difference between M365 and M367 matters in both clinical and harm reduction contexts. The M367’s 10 mg hydrocodone dose is double the M365’s 5 mg dose, meaning misuse at equivalent tablet counts delivers twice the opioid load and carries a proportionally higher overdose risk.

How Is M367 Used?

When prescribed, M367 is taken orally as one tablet every 4 to 6 hours as needed for pain, with a maximum of six tablets in a 24-hour period. According to the National Institutes of Health, the generally accepted therapeutic dose range is 5 to 10 mg of hydrocodone every 4 to 6 hours, with acetaminophen not exceeding 4,000 mg daily from all sources combined. Treatment is intended to begin at the lowest effective dose and be tapered slowly when discontinued to reduce withdrawal risk.

Misuse of M367 takes several forms beyond prescribed oral use:

• Taking more than prescribed: The most common form of misuse. Users increase their dose to achieve stronger pain relief or euphoria as tolerance builds, accelerating the path to physical dependence.
• Taking without a prescription: M367 is frequently diverted from prescriptions and sold or shared. Possession without a valid prescription is a felony under federal law.
• Crushing and snorting: Crushing the tablet and insufflating the powder bypasses the gradual oral absorption process, delivering hydrocodone to the brain more rapidly and intensifying the euphoric effect. This method significantly raises overdose risk.
• Combining with alcohol or benzodiazepines: Both alcohol and benzodiazepines are CNS depressants that compound hydrocodone’s respiratory depression. This combination is responsible for a substantial portion of prescription opioid overdose deaths.
• Using to manage withdrawal from other opioids: Some individuals use M367 to manage withdrawal symptoms from heroin or other opioids, which sustains dependence rather than treating it.

What Does M367 Feel Like?

At therapeutic doses, M367 produces effective pain relief along with mild sedation, relaxation, and a sense of physical comfort. For patients with genuine moderate to severe pain, the medication allows functional improvement that non-opioid analgesics have not provided. These effects are the intended clinical outcome when M367 is used as prescribed under medical supervision.

At higher doses or when misused, the effects of M367 include:

• Intense euphoria and a warm, full-body sense of well-being driven by hydrocodone’s opioid receptor activity
• Deep sedation, drowsiness, and physical heaviness
• Reduced anxiety and emotional blunting, which drives use among people self-medicating depression, PTSD, or chronic stress
• Impaired coordination, slowed reaction time, and cognitive dulling
• Nausea and vomiting, particularly in opioid-naive users or at high doses
• Constipation and urinary retention from opioid’s effect on the smooth muscle and digestive system
• Slowed breathing and reduced heart rate, which become dangerous at high doses or in combination with other depressants

The euphoric effect of M367 at non-therapeutic doses is what drives misuse and the development of addiction. As tolerance develops, users require increasingly higher doses to achieve the same euphoria, a cycle that progressively raises the risk of overdose with each tolerance escalation.

Why Is M367 Dangerous?

M367 carries two distinct and compounding overdose risks: opioid toxicity from hydrocodone and hepatotoxicity from acetaminophen. Most prescription opioid misuse focuses on the opioid component, but the acetaminophen in M367 creates a second serious and often overlooked danger that can cause irreversible liver damage before any opioid overdose symptoms are visible.

Hydrocodone at high doses suppresses the brainstem’s respiratory drive, causing breathing to slow and stop. This is the same mechanism that makes all opioids potentially fatal in overdose. The risk increases substantially when M367 is combined with alcohol, benzodiazepines, sleep aids, muscle relaxants, or other opioids, each of which adds its own CNS depressant effect to hydrocodone’s.

Specific danger factors for M367 misuse include:

• Acetaminophen accumulation: Six tablets of M367 per day delivers 1,950 mg of acetaminophen from M367 alone. Many users also take over-the-counter medications containing acetaminophen (Tylenol, NyQuil, DayQuil) without accounting for combined intake. The FDA recommends adults not exceed 4,000 mg of acetaminophen daily; chronic consumption at or above this level causes progressive liver damage that may not produce symptoms until organ failure is advanced.
• Rapid tolerance development: Hydrocodone dependence develops quickly, often within weeks of regular use. As tolerance builds, users take more tablets per dose, raising both opioid and acetaminophen intake simultaneously and compressing the margin between therapeutic and toxic doses.
• Drug interactions: M367 interacts dangerously with alcohol, benzodiazepines, other opioids, monoamine oxidase inhibitors (MAOIs), and tricyclic antidepressants. Each combination increases the risk of respiratory depression, sedation, and fatal overdose.
• Counterfeit pill risk: Illicitly manufactured pills that appear identical to M367 have been found to contain fentanyl. The DEA has documented widespread distribution of counterfeit hydrocodone and oxycodone pills pressed to match legitimate imprints. A person who obtains M367 outside of a licensed pharmacy has no reliable way to verify what the pill contains.

M367 Risk Profile Compared to Similar Pills

M367 Overdose: Signs and What to Do

An M367 overdose can result from hydrocodone toxicity, acetaminophen toxicity, or both simultaneously. Hydrocodone overdose produces visible, rapid-onset emergency symptoms. Acetaminophen overdose may be silent for 24 to 72 hours before causing acute liver failure, which is why any suspected M367 overdose requires emergency medical evaluation even when the person appears initially stable.

Signs of an M367 hydrocodone overdose include:

• Very slow, shallow, or stopped breathing
• Extreme drowsiness or inability to be awakened
• Blue or gray discoloration of the lips, fingertips, or skin (cyanosis)
• Cold, clammy, pale skin
• Pinpoint pupils (extremely small, even in low light)
• Limp body and loss of muscle tone
• Gurgling or choking sounds
• Loss of consciousness
• Slow or irregular heartbeat

Call 911 immediately. Administer naloxone (Narcan) right away if available. Naloxone reverses the opioid component of the overdose by blocking hydrocodone at opioid receptors. Multiple doses may be required if a counterfeit pill containing fentanyl was consumed. Place the person in the recovery position (on their side) to prevent choking. Stay with them and do not leave until emergency services arrive. All 50 US states have Good Samaritan laws providing legal protection to callers in overdose situations.

M367 Addiction: Signs and Symptoms

Hydrocodone in M367 drives opioid use disorder through the same neurological mechanism as heroin, fentanyl, and other opioids: repeated activation of the brain’s reward system causes opioid receptors to downregulate, producing tolerance and physical dependence. The person no longer uses M367 to manage pain or get high. They use it to avoid withdrawal and feel normal. According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), this pattern meets the clinical criteria for opioid use disorder.

Signs that someone has developed M367 addiction include:

• Taking M367 in larger amounts or more often than prescribed, or continuing use beyond the prescribed period
• Doctor shopping or obtaining M367 without a valid prescription
• Hiding pill use from family members, physicians, or employers
• Significant tolerance increase, requiring more tablets for the same effect
• Withdrawal symptoms when unable to access M367, including muscle aches, sweating, nausea, and anxiety
• Continued use despite documented health consequences including liver damage, falls, or impaired driving incidents
• Spending significant time and money obtaining M367 at the expense of work, family, and other responsibilities
• Inability to stop despite repeated attempts and genuine desire to quit

What Happens During M367 Withdrawal?

M367 withdrawal is opioid withdrawal driven by hydrocodone dependence. Symptoms begin within 12 to 48 hours of the last dose for immediate-release hydrocodone, peak between 48 and 72 hours, and the most severe acute symptoms resolve within 7 to 10 days. Post-acute withdrawal syndrome (PAWS), which includes depression, anxiety, sleep disturbance, and persistent cravings, can continue for weeks to months and is a primary driver of relapse after initial detox.

Early withdrawal symptoms (12 to 48 hours):

• Anxiety, restlessness, and irritability
• Muscle aches, joint pain, and leg cramps
• Excessive yawning, watery eyes, and runny nose
• Sweating, chills, and goosebumps
• Insomnia and inability to stay asleep

Peak withdrawal symptoms (48 to 72 hours):

• Nausea, vomiting, diarrhea, and abdominal cramping
• Rapid heart rate and elevated blood pressure
• Dilated pupils and heightened sensitivity to pain
• Severe cravings for M367 or any opioid
• Profound dysphoria and difficulty experiencing pleasure

M367 withdrawal is rarely fatal in isolation, but dehydration from persistent vomiting and diarrhea can become life-threatening without medical monitoring. The psychological weight of opioid withdrawal, particularly the dysphoria and cravings, drives most unsupported individuals back to using within the first 72 hours. For a complete phase-by-phase breakdown of what to expect, our opioid withdrawal timeline covers the full process of opioid detox.

M367 Drug Detection Windows

M367 is detected on standard drug screenings through its hydrocodone content. Hydrocodone will appear as a positive opiate or opioid result on urine, blood, saliva, and hair tests. Detection windows vary based on dose, frequency of use, individual metabolism, liver function, and body composition.

• Urine: 2 to 4 days for occasional use; up to 7 days for chronic or heavy use. Urine testing is the most commonly used method for workplace, legal, and clinical drug screening.
• Blood: 12 to 24 hours after last dose. Blood testing is the most accurate method for confirming very recent use but is used primarily in emergency and forensic settings.
• Saliva: 12 to 36 hours after last dose. Saliva testing is increasingly used in roadside law enforcement and employer programs for detecting recent impairment.
• Hair follicle: Up to 90 days after last use, and longer with extended heavy use. Hair testing provides the broadest historical window and is the most difficult to falsify.

A positive hydrocodone result on a drug test should be disclosed with the associated prescription information if legitimately prescribed. When no valid prescription exists, a positive result is a clinical indicator of opioid misuse that should factor into treatment and legal planning accordingly.

Treatment for M367 Addiction at Still Detox

M367 addiction is prescription opioid use disorder, and it requires the same evidence-based clinical treatment that produces lasting recovery from heroin and other opioid dependencies. The fact that M367 originated as a legitimate prescription does not reduce its addiction severity or change what recovery requires. Still Detox provides medically supervised opioid detox and residential treatment at our Boca Raton, Florida facility.

Our approach to treating M367 addiction includes:

• Medical detox: 24-hour physician and nursing supervision to manage opioid withdrawal safely, with medications including buprenorphine to reduce the severity of withdrawal symptoms and lower early relapse risk during the most physically demanding days of detox.
• Medication-assisted treatment (MAT): FDA-approved medications for opioid use disorder directly target the hydrocodone dependence driving M367 addiction. Our medication-assisted treatment FAQ explains how buprenorphine, methadone, and naltrexone work and which option fits different clinical presentations.
• Dual diagnosis treatment: M367 misuse frequently begins as pain management and evolves alongside untreated depression, anxiety, or PTSD that the opioid was also suppressing. Our dual diagnosis program treats both the addiction and any co-occurring mental health conditions simultaneously, which consistently produces better long-term outcomes than addressing either in isolation.
• Opioid-specific behavioral therapy: Cognitive behavioral therapy (CBT) and contingency management have the strongest clinical evidence base for opioid use disorder. For a full overview of our approach to prescription opioid addiction, our opioid addiction treatment program provides the clinical structure needed for lasting recovery.
• Fentanyl protocol: Because counterfeit pills mimicking M367 have been documented to contain illicit fentanyl, our clinical team screens for and treats fentanyl co-dependence as a potential component of any prescription opioid addiction presentation. Our fentanyl addiction program addresses this layer of dependence directly.

Recovery from M367 addiction is possible. Opioid use disorder driven by prescription hydrocodone responds to treatment at the same rates as any other form of opioid dependence. The Still Detox admissions team is available 24 hours a day, 7 days a week.

Frequently Asked Questions

What is the M367 pill used for?

M367 is a prescription pain medication used to treat moderate to severe pain that has not responded to non-opioid analgesics. It contains 10 mg of hydrocodone, an opioid, and 325 mg of acetaminophen, a non-opioid pain reliever. It is prescribed after surgery, injury, and for certain chronic pain conditions under close physician supervision. It is not intended for long-term use except in specific clinical circumstances where risks and benefits have been carefully evaluated.

Is M367 the same as Vicodin?

Yes. M367 is a generic equivalent of Vicodin at the 10/325 mg strength. Vicodin, Norco, and Lortab are brand names for the same hydrocodone-acetaminophen combination. M367 is manufactured by Mallinckrodt Pharmaceuticals and contains the same active ingredients at the same doses. The only differences are the manufacturer, physical imprint, and pill appearance. All versions carry identical clinical effects, risks, and addiction potential.

Can M367 cause addiction?

Yes. M367 contains hydrocodone, a Schedule II opioid with high addiction potential. Physical dependence can develop within weeks of regular use, even when the medication is taken exactly as prescribed. The risk increases significantly with misuse, dose escalation, and long-term use beyond the prescribed period. People with a personal or family history of substance use disorder, depression, anxiety, or chronic pain are at elevated risk of developing M367 addiction.

What happens if you take too many M367 pills?

Taking too many M367 pills creates two simultaneous overdose risks. The hydrocodone component suppresses the brain’s respiratory drive, causing breathing to slow and potentially stop, which is the classic opioid overdose mechanism. The acetaminophen component, at doses above 4,000 mg per day, causes progressive liver damage that can lead to acute liver failure within 72 hours. Both are medical emergencies. Call 911 immediately if an overdose is suspected, administer naloxone if available for the opioid component, and do not wait for symptoms to worsen before seeking help.

How long does M367 stay in your system?

Hydrocodone from M367 is detectable in urine for 2 to 4 days after the last dose in occasional users, and up to 7 days in chronic or heavy users. In blood, it is detectable for 12 to 24 hours. In saliva, detection windows range from 12 to 36 hours. Hair follicle testing can detect hydrocodone use for up to 90 days after the last dose. These windows vary based on dose, frequency, individual metabolism, and liver and kidney function.

What is the difference between M365 and M367?

Both M365 and M367 are white oval tablets manufactured by Mallinckrodt Pharmaceuticals containing hydrocodone and acetaminophen, but they differ in hydrocodone dose. M365 contains 5 mg of hydrocodone and 325 mg of acetaminophen, making it appropriate for mild to moderate pain. M367 contains 10 mg of hydrocodone and 325 mg of acetaminophen, making it a stronger formulation prescribed for moderate to severe pain. Misusing M367 at the same tablet count as M365 delivers double the opioid dose.

References

1. Rosenblum, A., et al. (2024). Hydrocodone and acetaminophen. StatPearls. National Institutes of Health. https://www.ncbi.nlm.nih.gov/books/NBK538530/
2. Drug Enforcement Administration (DEA). (2023). Drug scheduling: Hydrocodone. U.S. Department of Justice. https://www.dea.gov/drug-information/drug-scheduling
3. U.S. Food and Drug Administration (FDA). (2023). FDA drug safety communication: FDA warns about serious risks and death when combining opioid pain or cough medicines with benzodiazepines. https://www.fda.gov/drugs/drug-safety-and-availability
4. Centers for Disease Control and Prevention (CDC). (2023). Understanding the opioid overdose epidemic. https://www.cdc.gov/opioids/basics/epidemic.html
5. National Institute on Drug Abuse (NIDA). (2021). Prescription opioids DrugFacts. National Institutes of Health. https://nida.nih.gov/publications/drugfacts/prescription-opioids
6. Trescot, A. M., et al. (2023). Opioid withdrawal. StatPearls. National Institutes of Health. https://www.ncbi.nlm.nih.gov/books/NBK526012/
7. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). American Psychiatric Publishing.
8. MedlinePlus. (2023). Hydrocodone combination products. U.S. National Library of Medicine. https://medlineplus.gov/druginfo/meds/a601006.html