Niacin, also called nicotinic acid, is a B vitamin (vitamin B3). It occurs naturally in plants and animals, and is also added to many foods as a vitamin supplement. Niacin is also present in many multiple vitamins and nutritional supplements.

Simvastatin is in a group of drugs called HMG CoA reductase inhibitors, or "statins." Simvastatin reduces levels of "bad" cholesterol (low-density lipoprotein, or LDL) and triglycerides in the blood, while increasing levels of "good" cholesterol (high-density lipoprotein, or HDL).

The combination of niacin and simvastatin is used to lower cholesterol and triglycerides (types of fat) in the blood.

Niacin and simvastatin may also be used for purposes not listed in this medication guide.

You should not take this medication if you are allergic to niacin (Niaspan, Niacor, and others) or simvastatin (Zocor, Vytorin), if you are pregnant or breast-feeding, or if you have liver disease, severe bleeding, or a stomach ulcer.

In rare cases, simvastatin can cause a condition that results in the breakdown of skeletal muscle tissue, leading to kidney failure. Call your doctor right away if you have unexplained muscle pain, tenderness, or weakness especially if you also have fever, unusual tiredness, and dark colored urine.

Never take niacin and simvastatin in larger amounts, or for longer than recommended by your doctor. Follow your doctor's dosing instructions very carefully. Taking too much of this medication may cause serious or life-threatening side effects.

There are many other drugs that should not be used together with niacin and simvastatin. Tell your doctor about all medications you use. Keep a list of all your medicines and show it to any healthcare provider who treats you.

Simvastatin can harm an unborn baby or cause birth defects. Do not use niacin and simvastatin if you are pregnant.

Before taking niacin and simvastatin, tell your doctor if you have ever had liver or kidney disease, diabetes, gout, or a thyroid disorder, if you are of Chinese descent, or if you drink more than 2 alcoholic beverages daily.

You should not take this medication if you are allergic to niacin (Niaspan, Niacor, and others) or simvastatin (Zocor, Vytorin), if you are pregnant or breast-feeding, or if you have liver disease, severe bleeding, or a stomach ulcer.

In rare cases, niacin and simvastatin can cause a condition that results in the breakdown of skeletal muscle tissue, leading to kidney failure. This condition may be more likely to occur in older adults and in people who have kidney disease or poorly controlled hypothyroidism (underactive thyroid). You may also be more likely to develop this condition if you are of Chinese descent

The following drugs can increase your risk of serious muscle problems if you take them together with simvastatin. These drugs should not be used while you are taking niacin and simvastatin:

• amiodarone (Cordarone, Pacerone);

• cyclosporine (Gengraf, Neoral, Sandimmune);

• danazol (Danocrine);

• diltiazem (Cartia, Cardizem, Tiazac);

• gemfibrozil (Lopid);

• nefazodone (an antidepressant);

• verapamil (Calan, Covera, Isoptin, Verelan);

• the antibiotics clarithromycin (Biaxin), erythromycin (E.E.S., EryPed, Ery-Tab, Erythrocin), and telithromycin (Ketek);

• the antifungal medications itraconazole (Sporanox), ketoconazole (Nizoral), and posaconazole (Noxafil); or

• the HIV/AIDS medications atazanavir (Reyataz), darunavir (Prezista), fosamprenavir (Lexiva), nelfinavir (Viracept), ritonavir (Norvir, Kaletra), saquinavir (Invirase), and tipranavir (Aptivus).

Before you start taking niacin and simvastatin, tell your doctor if you are already using any of these other medicines:

• amlodipine (Norvasc, Caduet, Exforge, Lotrel, Tekamlo, Tribenzor, Twynsta, Amturnide); or

• ranolazine (Ranexa).

To make sure you can safely take niacin and simvastatin at any dose, tell your doctor if you have any of these other conditions:

• history of liver disease;

• history of kidney disease;

• diabetes;

• gout;

• a thyroid disorder;

• if you drink more than 2 alcoholic beverages daily; or

• if you are switched to this medication from regular niacin, nicotinic acid, or nicotinamide (or vitamin supplements that contain niacin).

FDA pregnancy category X. This medication can harm an unborn baby or cause birth defects. Do not take niacin and simvastatin if you are pregnant.Stop taking this medication and tell your doctor right away if you become pregnant. Use effective birth control to avoid pregnancy while you are taking niacin and simvastatin.

Niacin and simvastatin may pass into breast milk and could harm a nursing baby. Do not breast-feed while you are taking niacin and simvastatin.