how long can I safely take methimazole?

Answer 1

As long as it is needed to correct the hyperthyroidism. Your doctor should be monitoring your levels each month to determine that it is working. Otherwise, if the medication is not doing its job, you need to be switched to a method which does work. Some folks go to PTU (medication), others opt for the radioactive iodine or surgery to remove part of the thyroid (called a subpartial thyroidectomy).

Your endocrinologist will guide you -- have faith.

Answer 2

Before taking Methimazole
Tell your healthcare provider and pharmacist if you are allergic to methimazole, propylthiouracil, lactose, or any other drugs.
Tell your healthcare provider and pharmacist what prescription and nonprescription medications you are taking, especially anticoagulants ('blood thinners') such as warfarin (Coumadin), beta blockers such as propranolol (Inderal), diabetes medications, digoxin (Lanoxin), theophylline (Theobid, Theo-Dur), and vitamins.
Tell your healthcare provider if you have or have ever had any blood disease, such as decreased white blood cells (leukopenia), decreased platelets (thrombocytopenia), or aplastic anemia, or liver disease (hepatitis, jaundice).
Tell your healthcare provider if you are pregnant, plan to become pregnant, or are breast-feeding. An alterntive anti-thyroid drug, propylthiouracil is often substituted during pregnancy or breast-feeding. If you become pregnant while taking methimazole, discuss with your healthcare provider whether you should switch to propylthiouracil with your healthcare provider. Early studies suggested that methimazole may harm the fetus, although more recent studies suggest this may not be the case.
If you are having surgery, including dental surgery, tell the healthcare provider or dentist that you are taking Methimazole.