Studies comparing it to the benzodiazepine lorazepam and the antihistamine diphenhydramine, along with placebo, find that methocarbamol produces increased "liking" responses and some sedative-like effects; however, at higher doses dysphoria is reported. It is considered to have an abuse profile similar to, but weaker than, lorazepam. Interactions
Methocarbamol may inhibit the effects of pyridostigmine bromide. Therefore, methocarbamol should be used with caution in those with myasthenia gravis taking anticholinesterase medications.Methocarbamol may disrupt certain screening tests as it can cause color interference in laboratory tests for 5-hydroxy-indoleacetic acid (5-HIAA) and in urinary testing for vanillylmandelic acid (VMA) using the Gitlow method. Pharmacology
Mechanism of action
The mechanism of action of methocarbamol has not currently been established. Its effect is thought to be localized to the central nervous system rather than a direct effect on skeletal muscles. It has no effect on the motor end plate or the peripheral nerve fiber. The efficacy of the medication is likely related to its sedative effect. Alternatively, methocarbamol may act via inhibition of acetylcholinesterase, similarly to carbamate. Pharmacokinetics
In healthy individuals, 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%. The elimination half-life was longer in the elderly, those with kidney problems, and those with liver problems.
Lipoid pneumonia is a specific form of lung inflammation (pneumonia) that develops when lipids enter the bronchial tree. The disorder is sometimes called cholesterol pneumonia in cases where that lipid is a factor. Signs and symptoms
The pneumonia presents as a foreign body reaction causing cough, dyspnea, and often fever. Hemoptysis has also been reported. Causes
Sources of such lipids could be either exogenous or endogenous.Exogenous: from outside the body. For example, inhaled nose drops with an oil base, or accidental inhalation of cosmetic oil. Amiodarone is an anti-arrythmic known to cause this condition. Oil pulling has also been shown to be a cause. Fire breathers pneumonia from the inhalation of hydrocarbon fuel is a specific variant. At risk populations include the elderly, developmentally delayed or persons with gastroesophageal reflux. Switching to water-soluble alternatives may be helpful in some situations.Endogenous: from the body itself, for example, when an airway is obstructed, it is often the case that distal to the obstruction, lipid-laden macrophages and giant cells fill the lumen of the disconnected airspace. Appearance
The gross appearance of a lipid pneumonia is that in which there is an ill-defined, pale yellow area on the lung. This yellow appearance explains the colloquial term "golden" pneumonia. At the microscopic scale foamy macrophages and giant cells are seen in the airways, and the inflammatory response is visible in the parenchyma. Treatment
Treatment is with corticosteroids and possibly intravenous immunoglobulins. Prognosis
Endogenous lipoid pneumonia and non-specific interstitial pneumonitis has been seen prior to the development of pulmonary alveolar proteinosis in a child.