If you are currently being treated with any of the following medications, you should not use cysteine supplements without first talking to your health care provider.

Blood pressure medications, angiotensin-converting enzyme (ACE) inhibitors -- NAC may enhance the blood pressure-lowering effects of ACE inhibitors, medications commonly used to treat high blood pressure. Examples of ACE inhibitors include benazepril (Lotensin), captopril (Capoten), enalapril (Vasotec), and lisinopril (Prinivil).

Immunosuppressive medications -- Treatment with NAC may enhance the effectiveness of immunosuppressive medications such as azathioprine (Imuran), cyclophosphamide (Cytoxan), or prednisone (Deltasone). More research in this area is needed.

Cisplatin and doxorubicin -- Laboratory and animal studies have suggested that NAC may reduce the toxic effects associated with both cisplatin (Platinol) and doxorubicin (Ardiamycin), medications used to treat a variety of cancers. However, scientific studies are needed to see if these effects apply to people.

Nitroglycerin and isosorbide -- Although NAC may enhance the effectiveness of nitroglycerin and isosorbide (Isordil), two medications commonly used to treat chest pain. This combination may also increase the risk of side effects such as severe headaches and may lead to abnormally low blood pressure.

Oxiconazole -- Topical applications of NAC may increase the effectiveness of oxiconazole (Oxistat), an antifungal medication used for athlete's foot.