The pill marked with the imprint M366 is a combination prescription pain reliever containing hydrocodone bitartrate and acetaminophen. This medication belongs to the class of narcotic analgesic combinations, designed to treat pain that is moderate to moderately severe. The M366 imprint identifies a product manufactured by Mallinckrodt Pharmaceuticals. It helps patients, pharmacists, and medical professionals correctly recognize the specific drug and dosage.
Identification and Composition of the M366 Pill
The physical appearance of the M366 pill is a white, oval-shaped tablet. The tablet is debossed with the identifying code “M366” on one side. This physical marking confirms the pill’s identity and helps distinguish it from other medications.
The combination of active ingredients is 7.5 milligrams (mg) of hydrocodone bitartrate and 325 mg of acetaminophen. Hydrocodone is an opioid analgesic, a potent pain reliever. Acetaminophen is a non-opioid pain reliever and fever reducer.
The presence of both components means the medication works through two distinct mechanisms simultaneously. This dual-action approach provides more effective pain relief than either ingredient could offer alone. The specific ratio of 7.5 mg of hydrocodone to 325 mg of acetaminophen represents a commonly prescribed strength.
Medical Purpose and Administration Guidelines
The primary approved use for the M366 pill is the management of pain severe enough to require an opioid, typically pain that has not responded adequately to non-opioid medications. Hydrocodone functions by changing the body’s perception of pain signals. Acetaminophen contributes by raising the body’s pain threshold and works synergistically with the opioid component to enhance the overall analgesic effect.
Patients are instructed to take one tablet every four to six hours as needed for pain. The duration of use is limited to the shortest possible time to manage acute pain, such as following surgery or injury. The medication can be taken with or without food.
A significant administration guideline involves the acetaminophen component. Because each tablet contains 325 mg of acetaminophen, a patient must strictly track their total daily intake from all sources, including over-the-counter cold remedies or other pain relievers. The maximum recommended daily dosage of acetaminophen for healthy adults is generally 4,000 mg, though some healthcare professionals advise a more conservative limit of 3,000 to 3,250 mg to minimize the risk of liver damage.
Safety Profile and Critical Warnings
The combination of hydrocodone and acetaminophen carries two distinct sets of serious risks, stemming from the potential for abuse and organ toxicity. Hydrocodone, as an opioid, poses the risk of developing tolerance, physical dependence, and addiction, even when taken exactly as prescribed. Tolerance occurs when the body adapts to the drug, requiring higher doses for the same pain relief.
The most serious risk associated with the opioid component is respiratory depression, which is a potentially life-threatening slowing or shallowing of breathing. The risk of severe sedation, coma, and respiratory failure increases dramatically when this medication is combined with other central nervous system (CNS) depressants.
CNS depressants include alcohol, benzodiazepines, and certain sedatives or muscle relaxants. The additive depressant effect from these combinations can lead to profound sedation and an increased risk of a fatal overdose. Common side effects of the medication include constipation, nausea, dizziness, and drowsiness.
The acetaminophen component introduces a separate danger: hepatotoxicity, or severe liver damage. Exceeding the maximum recommended daily dose can deplete the liver’s ability to process the drug safely. This can lead to acute liver failure, which may require a liver transplant or result in death. Patients with pre-existing liver disease or those who consume three or more alcoholic drinks per day face a greater risk of acetaminophen-related injury.
Regulatory Status and Prescription Requirements
Due to the presence of hydrocodone, the M366 pill is classified in the United States as a Schedule II controlled substance under the federal Controlled Substances Act (CSA). This classification is reserved for drugs with a currently accepted medical use but with a high potential for abuse and dependence. This designation imposes strict regulations on how the medication is prescribed and dispensed.
Federal law prohibits refills for Schedule II medications; a new prescription must be issued by a healthcare provider each time the patient needs more medication. This requirement often means a patient must see their provider more frequently to maintain therapy. Prescribers may issue multiple prescriptions for a total supply of up to 90 days, provided each prescription indicates the earliest date it can be filled.
In most states, the prescription is subject to a time limit, such as becoming invalid 30 days after the date it was written.