It is very important that your doctor check your progress closely while you are using this medicine to see if it is working properly and to allow for a change in the dose. Blood tests may be needed to check for any unwanted effects.
Do not stop taking this medicine without first checking with your doctor. Stopping suddenly may cause a serious change in heart function.
Watch for signs and symptoms of overdose while you are taking this medicine. Follow your doctor's directions carefully. The amount of this medicine needed to help most people is very close to the amount that could cause serious problems from overdose. Some early warning signs of overdose are loss of appetite, nausea, vomiting, diarrhea, or problems in seeing. Other signs of overdose are changes in the rate or rhythm of the heartbeat (becoming irregular or slow), palpitations (feeling of pounding in the chest), or fainting. In infants and small children, the earliest signs of overdose are changes in the rate and rhythm of the heartbeat. Children may not show the other symptoms as soon as adults.
Your doctor may want you to carry a medical identification card or bracelet stating that you are receiving this medicine.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.
Before having any tests, tell your doctor that you are using this medicine. This medicine may affect the results of certain medical tests.