Pyridostigmine bromide is a medication used for the treatment of myasthenia gravis. It's not officially FDA-approved for use in animals, but veterinarians prescribe pyridostigmine as an extra-label drug. That means the drug can be legally prescribed for medical use in a species or for a condition that isn't specifically approved by the FDA.
Myasthenia gravis is caused by insufficient acetylcholine receptors on the postsynaptic membranes, causing impaired transmission of nerve impulses to the muscles. The result is generalized muscle weakness, often concentrated in the esophagus, that's exacerbated by activity and eased by rest. Myasthenia gravis can be an inherited congenital disorder or an acquired disorder that develops after birth.
Pyridostigmine is an anticholinesterase medication belonging to a drug class of cholinesterase inhibitors. It prevents cholinesterase enzymes from destroying acetylcholine, which increases acetylcholine concentrations and enables it to reach acetylcholine receptors, allowing muscles to contract normally and with more strength.
Side effects, usually linked to high dosage and resolved by dose reduction, include vomiting, diarrhea, salivation, respiratory difficulty, increased lung secretions, pupil constriction, compromised vision, tearing, change in heart rate, cholinergic crisis, muscle cramps and weakness. Pyridostigmine should not be given to dogs with urinary or intestinal obstructions, dogs who are pregnant or dogs who have bromide allergies or hypersensitivity.
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