It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.
Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away.
Do not use niacin/simvastatin if you are also using the following medicines: boceprevir (Victrelis®), cyclosporine (Gengraf®, Neoral®, Sandimmune®), danazol (Danocrine®), gemfibrozil (Lopid®), nefazodone (Serzone®), telaprevir (Incivek®), certain antibiotics (such as clarithromycin, erythromycin, itraconazole, ketoconazole, posaconazole, telithromycin, Nizoral®), certain blood pressure medicines (such as diltiazem, verapamil, Calan®, Cardizem®, Verelan®), or certain medicines to treat HIV/AIDS (such as atazanavir, indinavir, nelfinavir, ritonavir, saquinavir, Crixivan®, Kaletra®, Lexiva®, Norvir®, Prezista®, Reyataz®). Using these medicines together can cause serious side effects.
Call your doctor right away if you have unexplained muscle pain, tenderness, or weakness. These may be symptoms of serious muscle problems, such as myopathy or immune-mediated necrotizing myopathy (IMNM). Myopathy is more common when high doses of simvastatin (e.g., 80 milligrams) are used, but some people get myopathy with lower doses.
Call your doctor right away if you have dark-colored urine, diarrhea, a fever, muscle cramps or spasms, muscle pain or stiffness, or feel very tired or weak. These could be symptoms of a serious muscle problem called rhabdomyolysis, which can cause kidney problems.
Chinese patients who are taking large amounts of niacin (greater than or equal to 1 gram or 1000 milligrams per day) together with simvastatin may have an increased risk for muscle injury. Talk to your doctor if you are Chinese or have Chinese ancestry and take large amounts of niacin (Niacor®, Niaspan®). Your doses of niacin/simvastatin should not be more than 1000 mg/20 mg per day.
Make sure your doctor or dentist knows that you are using this medicine. Stop using this medicine several days before having surgery or medical tests. This medicine may affect the results of certain medical tests. You may also need to stop using this medicine if you have a major surgery, a major injury, or you develop other serious health problems.
Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, unusual tiredness or weakness, or yellow eyes or skin. These could be symptoms of liver damage.
This medicine may affect blood sugar levels. This is important if you are diabetic or prediabetic. If you notice a change in the results of your blood or urine sugar tests, or if you have any questions, check with your doctor.
This medicine may cause some people to become dizzy, lightheaded, drowsy, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are not alert. Change positions slowly when getting up from a sitting or lying position.
This medicine should not be taken with vitamins containing niacin or nicotinamide.
This medicine may cause a side effect called flushing. Flushing is a feeling of warmth or redness on the face, neck, arms, and occasionally, on the upper chest. To avoid flushing, alcohol, hot beverages, and spicy foods should be avoided around the time you take this medicine. Additionally, your doctor may recommend that you take aspirin 30 minutes before taking this medicine to prevent flushing.
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.