In terms of the standard elimination of methadone’s effects, most sources are inconsistent revealing different methadone half-lives ranging from 24-36 hours, 13-47 hours, 15-40 hours, and 8-59 hours. With the data, it only means that methadone half-life varies between individuals.
- Methadone is efficiently absorbed by the gastrointestinal (GI) tract after taking it orally. Within half an hour after gastrointestinal tract absorption, the methadone levels are cleared in plasma and medication hits its peak in about 4 hours after ingestion.
- Methadone’s bioavailability is generally around 80 percent, but varies between 36 percent to 100 percent.
What Makes Methadone Stay Longer In The System?
Varying forms of Methadone differ in its systemic clearance time due to many factors such as the individual’s frequency of ingestion, the dosage, modality of drug entry, and co-ingestion with other substances. These factors expedite clearance in less than 2 days in most people, while others can hold it up until in longer periods of time.
Even if two individuals take 10mg of methadone together, one of them can dispel the medication faster from the system than the other individual because of specific factors. Unique elements that influence methadone ingestion, digestion, and clearance include age, body mass, genetics and liver functionality.
Elderly individuals (ages 65 above) metabolize and excrete drugs slower than adolescents and adults. This is due to their poorer organ functionality (liver or kidneys), reduced hepatic blood flow, medical issues, less efficient physiologic functions, a slower rate of metabolism, as well as ingestion of other medications.
Dosage (5 mg to 40 mg)
Methadone may clear longer from the body if the person ingests a bigger dosage. It should follow that when a smaller dose is taken in, it will result in faster excretion from the body. Those taking high doses, on the other hand, may have more of this drug in their lipids and can crush various liver enzymes like CYP3A4. Moreover, high dosage may extend excretion times. The amount ingested with respect to body mass can also affect clearance.
Steady levels and maximum excretion effects are not typically attained for at least 3 to 5 days of treatment. About 90 percent of methadone still mixes to plasma proteins (like a1-acid glycoprotein) and is circulated generally in tissues after absorption.
Most ingested parent metabolites like its EDDP are flushed out through urination. Smaller amounts are excreted through bile, feces, and sweat. Since the half-life ranges from 8 to 59 hours, the average half-life would be 33.5 hours. Hence, the complete time of clearance of methadone from the system will probably take around 7.68 days.
Methadone can be detected with a urine test after an hour since the last intake and may last 2 weeks post-ingestion. Urine tests are often preferred over blood tests because they are non-invasive and offer a long detection period.