Commentary: Is Polyethylene Glycol Toxicity From Intravenous Methocarbamol Fact or Fiction?

Methocarbamol is an antispasmodic muscle relaxant and was the fourth most-prescribed muscle relaxant by volume in the United States in 2021. Intravenous (IV) methocarbamol contains the excipient, polyethylene glycol (PEG), which has been implicated in metabolic acidosis and nephrotoxicity. Intravenous methocarbamol was first approved by the US Food and Drug Administration in 1959 and at that time the IV methocarbamol prescribing information warned of PEG-associated adverse drug events in patients living with renal impairment; however, the manufacturer acknowledged data were lacking to objectively support this claim. Clinicians prescribing and dispensing IV methocarbamol may encounter the warning for PEG-associated metabolic acidosis and nephrotoxicity without knowing the potential risks, or lack thereof, supporting or disavowing this phenomenon. This commentary debates the merits supporting and arguments refuting PEG-associated metabolic acidosis and nephrotoxicity in patients treated with IV methocarbamol.

COMET - effectiveness and tolerability of methocarbamol versus oral opioid-analgesics as add-on measure in patients with non-specific low back pain refractory to recommended 1st line treatments. A retrospective analysis of depersonalized propensity score matched open-label real-world 4-week data from the German Pain e-Registry.

BACKGROUND: To compare the 4-week effectiveness and tolerability of an add-on treatment with oral high dose methocarbamol (MET) vs long-acting oral opioid analgesics (LAO) in patients with non-specific low back pain (nsLBP) poorly responsive to recommended 1st line treatments. METHODS: Analysis of anonymized, propensity score-matched real-world data from the German Pain e-Registry, using a sequential non-inferiority superiority approach, for adult outpatients with nsLBP who had initiated treatment with MET or LAO between 1st January 2018 and 31st December 2019 (EUPAS identifier: 38484). The primary effectiveness variable was the absolute change of the average 24-h. pain intensity index (PIX). Safety was assessed by incidence of physician-confirmed drug-related adverse events (DRAEs), and DRAEs leading to discontinuation. RESULTS: Propensity score-matched data were analyzed for 374 patients treated with MET and 374 patients treated with LAO. Mean ± SD (median) MET dose over the 4-week evaluation period was 2390.4 ± 1980 (3000) mg and 69.6 ± 25.9 (60) mg morphine equivalent for LAO. With 25.8 ± 11.4 (median 26, 95%CI: 24.5-27.1) vs. 11.4 ± 6.8 (median 11; 95%CI: 10.6-12.2) mm VAS, absolute 4-week improvement vs. baseline was superior for MET vs. LAO [p < .001; effect size 1.6; least square mean difference 14.4 (95%CI: 13.4-15.3)]. Percentages of patients with a PIX improvement ≥ MCID was 81.8 vs. 24.6% [p < .001; OR: 13.8 (9.7-19.6), RR: 4.0 (3.2-5.0), NNT: 1.7]. A significantly lower number of patients treated with MET vs. LAO reported DRAEs in response to study medication: 36 (9.6%) vs. 139 (37.2%; p < .001; NNT 4), and 9 patients treated with MET (2.4%) vs. 86 (23.0%) treated with LAO discontinued treatment in response to these DRAEs (p < .001; NNT: 5). CONCLUSION: 4-week add-on treatment with MET in patients with nsLBP who showed an inadequate response to recommended 1st line treatments is superior effective to LAO and significantly better tolerated.KEY MESSAGESLow back pain is the most common musculoskeletal problem worldwide.In the majority of patients, LBP does not have a specific cause and the most prevalently coded form is mechanical, non-specific (ns) LBP associated with muscular tension, restrictions in mobility, and static malposition.Current treatment recommendations for nsLBP are largely "non-specific" as well, limited to symptomatic pain-relieving measures.In our propensity score-matched two cohort analyses of depersonalized real-world data from the German Pain e-Registry, a 4-week treatment with the muscle relaxant methocarbamol proved superior effective and significantly better tolerated than treatment with oral long-acting opioid analgesics in patients who poorly responded to recommended 1st line treatments.

Randomized-controlled trial of methocarbamol as a novel treatment for muscle cramps in cirrhotic patients.

BACKGROUND: Muscle cramps occur in 29-88% of patients with liver cirrhosis. They adversely affect quality of life. This study aimed to evaluate the efficacy and safety of methocarbamol as a novel therapy in controlling muscle cramps in cirrhotic patients. PATIENTS AND METHODS: This study was carried on 100 patients with liver cirrhosis in addition to chronic hepatitis C who presented with frequent muscle cramps (≥three cramps per week). Half of these patients received methocarbamol and the other half received placebo. This was done through equal randomization. Questionnaires on muscle cramp were answered. Patients were evaluated before, after 1 month of treatment, and 2 weeks after washout of treatment in terms of severity, duration, and frequency of cramps. Liver, renal functions, and electrolytes were analyzed. Also, any side effect was detected. RESULTS: Patients who were treated with methocarbamol showed a significant decrease in the frequency and duration of cramps. Also, the pain score improved significantly. However, no significant changes were observed in the placebo group. Few side effects of methocarbamol were recorded, including dry mouth and drowsiness. CONCLUSION: Methocarbamol seems to be a promising safe and well-tolerated medication, and plays a role in the treatment of muscle cramps in patients with liver cirrhosis.

A case report of unusual vasculitic reaction after Methocarbamol injection.

Descriptive case report of a 42-year old woman with coetaneous vasculitis, and severe abdominal pain, which was led to diagnostic laparotomy. These presentations are probably as a side effect of Methocarbamol injection. This is the first report according to our literature search (PubMed, google scholar, ISI web of knowledge, ProQuest, MD consult, Science Direct, SCOPUS) about Methocarbamol related vasculitis from 1966 since now. Vasculitis is not a known side effect of Methocarbamol. This case indicates, likely the potential for development of vasculitis with this medication.

How to try this: detecting delirium.

For patients and their loved ones, delirium can be a frightening experience. A fluctuating mental status is important to identify because it often signals a need for additional treatment. The Confusion Assessment Method (CAM) diagnostic algorithm enables nurses to assess for delirium by identifying the four features of the disorder that distinguish it from other forms of cognitive impairment. It can be completed in five minutes and is easily incorporated into ongoing assessments of hospitalized patients. (This screening tool is included in the series Try This: Best Practices in Nursing Care to Older Adults, from the Hartford Institute for Geriatric Nursing at New York University's College of Nursing.) For a free online video demonstrating the use of this tool, go to http://links.lww.com/A209.

Pain reduction in breast augmentation using methocarbamol.

Submuscular placement of breast implants produces significant postoperative pain and discomfort. The standard use of narcotics alone does not optimize pain reduction. Methocarbamol was used intraoperatively and postoperatively in 62 patients undergoing manipulation of the pectoralis major associated with breast implant surgery. Significant pain relief was achieved.

Urticaria of the colon.

The clinical manifestations of colonic urticaria vary, depending on the presence of associated abnormalities. A case of an association between colonic urticaria and cecal volvulus is described.

A double-blind trial of methocarbamol versus placebo in painful muscle spasm.

A double-blind trial of methocarbamol versus placebo was carried out in 59 matched pairs of patients suffering from painful muscle spasm. Methocarbamol (1500 mg. q.d.s.) was found to be effective in approximately 60% of patients compared with 30% of patients receiving placebo (p less than 0.01). Side-effects were of almost equal incidence in the two groups.