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Methocarbamol belongs
to class of centrally acting “muscle relaxant”.
Methocarbamol belongs to class of centrally acting “muscle
relaxant”. It is used to treat muscle pain and stiffness. It is generally used
with rest and physical therapy for the treatment of muscle pain and stiffness.
Pharmacological
class: Muscle relaxant
Methocarbamol is a central muscle relaxant for skeletal
muscles, used to treat spasms. It is structurally related to guaifenesin. The
exact mechanism of methocarbamol causing skeletal muscle relaxation is unknown.
It is thought to work centrally, perhaps by general depressant effects. It has
no direct relaxant effects on striated muscle, nerve fibers, or the motor
endplate. It will not directly relax contracted skeletal muscles. The drug has
a secondary sedative effect.
Usual Adult Dose for Muscle Spasm
Oral:
Initial dose: 1500 mg four times a day for the first 48 to
72 hours, up to a maximum dosage of 8 g/day for severe symptoms
Maintenance dose: 4000 to 4500 mg/day in divided doses
IV or IM: 1000 mg up to every 8 hours if necessary, not to exceed 3 g/day for more than 3 consecutive days except in the treatment of tetanus.
The plasma clearance of methocarbamol ranges between 0.20
and 0.80 L/h/kg, the mean plasma elimination half-life ranges between 1 and 2
hours, and the plasma protein binding ranges between 46% and 50%. Methocarbamol
is metabolized via dealkylation and hydroxylation. Conjugation of methocarbamol
also is likely. Essentially all methocarbamol metabolites are eliminated in the
urine. Small amounts of unchanged methocarbamol also are excreted in the urine.
Common (affecting between 1
in 10 to 1 in 100)
Uncommon (affecting 1 in 100 to 1 in 1000):
Very rare (affecting less than 1 in 10,000):
In a randomized, placebo
controlled multi-centre study, inclusion criteria were acute low back pain for
at least 24 h associated with spasms in the pelvic/lumbar region and
restriction of mobility. Patients were randomly assigned to a group treated
with orally administered methocarbamol (n = 98) or placebo (n = 104).
Individual pain perception was quantified by means of a visual analog scale
(VAS). The fingertip-to-floor distance was measured as an indicator of lumbar
flexion. Mobility restrictions were also assessed by a modified Schober's test.
In addition, a questionnaire was used by patients and physicians to rate the
efficacy of treatment. In methocarbamol
group 44% of the patients pre-terminated due to complete pain relief (placebo:
18%) and 19% discontinued because the treatment was considered ineffective
(placebo 52%, p < 0,0001). Measures of mobility and improvement of mobility
as perceived by physician and patient at the individual end of study all were
clearly in favor of the patients treated with methocarbamol. At the final
visit, 67% of the patients who had received methocarbamol (35% placebo
patients) and 70% of their physicians (control group: 36%) considered the
treatment to be effective. No severe adverse effects were observed during the
study. This study showed that methocarbamol, orally administered, is an
efficient and well-tolerated therapeutic option for patients suffering from
acute LBP and the typically associated restrictions of mobility.1
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