Methylcobalamin is a nerve-nourishing drug, generally 14-28 days is a course of treatment, patients need to maintain treatment for about 3 months, after taking 1 month if there is effect can continue to take, no need to stop the drug in between. Methylcobalamin is an important raw material for the synthesis of myelin sheath of peripheral nerves, and it is used to treat peripheral neuropathies with more indications, such as idiopathic facial neuritis, carpal tunnel syndrome, ulnar nerve injury, radial nerve palsy, trigeminal neuralgia, intercostal neuritis, etc. Usually, 14-28 days is a course of treatment. If the patient has no effect for 1 month, it is recommended to change the treatment plan promptly. If there is an effect, it is recommended to maintain the treatment for about 3 months. While patients take methylcobalamin, it is generally recommended to supplement vitamin B1 at the same time, so that the therapeutic effect of the drug can be better exerted. In addition, some patients taking methylcobalamin may also experience adverse reactions, including rash and allergy, which require discontinuation of the drug; it may also cause gastrointestinal symptoms such as loss of appetite, nausea, vomiting and diarrhea, but it is uncommon. Meanwhile, workers who work with mercury and its compounds should not take large amounts of this drug for a long time.