Robaxin is a brand name of the generic medication methocarbamol. Methocarbamol is a central nervous system depressant that is used to treat involuntary muscle spasms. Robaxin has a relatively short half-life. In healthy individuals, nearly all methocarbamol metabolites are excreted in the urine within four hours of ingesting the drug.
Mothers who are pregnant should avoid taking Robaxin due to an increased likelihood of the infant being born with congenital birth defects. Methocarbamol is present in the milk of lactating mothers receiving treatment with the drug. It is unknown whether this may be damaging to the development of nursing infants. Methocarbamol should be avoided when driving an automobile or operating heavy machinery due to the potential for impaired motor skills.
Methocarbamol is not a safe treatment for many elderly patients due to the increased risk for serious side effects. Common side effects of Robaxin may include upset stomach, flushing of the skin, poor coordination (ataxia), dizziness, blurred vision and drowsiness. Cases of rapid heart rate (tachycardia) and slow heart rate (bradycardia) have been reported on rare occasions. These are serious conditions and should be reported to the prescribing doctor immediately. Other side effects that are indicative of a poor reaction to the drug include itching, jaundice (yellow skin and eyes), fainting, nausea, vomiting, difficulty urinating, mood swings and abdominal pain. Incidences of increased suicidal thoughts are uncommon but are more likely to occur in young patients taking high doses of methocarbamol.
Robaxin is considered low-risk for developing a dependence on the drug. Abruptly stopping treatment can lead to the increased likelihood of side effects. Methocarbamol has a tendency for addiction like the benzodiazepine lorazepam, although the addictive qualities of methocarbamol are considerably weaker. Occurrences of addiction to methocarbamol alone is rare. Typical habits evolve in individuals with a history of addiction to other substances.
Robaxin has a high therapeutic index. This means that it tends to be effective and safe at a wide range of doses. Daily doses of 500 mg to 750 mg are common for the treatment of persistent involuntary muscles spasms. Significantly higher doses may be necessary for the treatment of lockjaw that’s associated with tetanus. Severe side effects are more likely to occur at higher doses. The exact mechanism of action of methocarbamol is unknown. Robaxin does not act directly on striatal muscle fibers but rather inhibits the functioning of the neurons that trigger the muscle twitching and pain. By depressing the activity of these neurons, symptoms can be reduced.
The plasma elimination half-life of methocarbamol ranges between one and two hours before being excreted in the urine. Nearly all of methocarbamol’s metabolites are excreted in the urine. Only a miniscule amount of methocarbamol itself is eliminated in the urine. The plasma protein binding of methocarbamol ranges from 46 percent to 50 percent in healthy individuals.
The patient’s age, the health of their kidneys and the health of their liver all influence the metabolism of Robaxin in the body. Elderly patients of a mean age of 69 take slightly longer to eliminate methocarbamol in the urine. Another way to say this is that methocarbamol has a shorter half-life in elderly patients. The elderly population with a mean age of 69 takes roughly 1.5 hours to eliminate Robaxin, while patients with a mean age of 53 take on average 1.1 hours to excrete the drug.
The older patients also display a decreased fraction of bound methocarbamol in the blood, meaning that younger patients utilize the drug more effectively. Patients on hemodialysis due to poorly functioning kidneys absorb and utilize methocarbamol less efficiently at a clearance rate of only 40 percent compared to 46 percent to 50 percent in healthy patients. Individuals with cirrhosis of the liver due to alcohol misuse have a similarly poor rate of effectiveness, with only 40 percent to 45 percent of methocarbamol bonding to plasma proteins.
Testable levels of methocarbamol metabolites may be present in the urine beginning one to two hours following ingestion. Methocarbamol can remain in the urine for up to four hours following the time of ingestion. These ranges can vary depending on the age and health of the patient. For most individuals, only two percent of absorbed methocarbamol will remain in the blood at 24 hours following the final dose of the drug. As is the case with most substances, Robaxin may be tested for via a hair sample within 90 days of the last treatment.
Mixing Robaxin With Alcohol
The Recovery Village aims to improve the quality of life for people struggling with substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare providers.