Safety Information
If you are taking any of the following medicines please communicate it to your physician:
Bosentan (Tracleer);
A blood thinner, for example, warfarin (Coumadin);
cimetidine (Tagamet, Tagamet HB);
An antibiotic like erythromycin (E-Mycin, Eryc, Ery-Tab) or clarithromycin (Biaxin);
Doxazosin (Cardura), prazosin (Minipress), Terazosin (Hytrin);
HIV medicines including amprenavir (Agenerase), tipranavir (Aptivus), darunavir (Prezista), efavirenz (Sustiva), nevirapine (Viramune), indinavir (Crixivan), saquinavir (Invirase, Fortovase), lopinavir/ritonavir (Kaletra), fosamprenavir (Lexiva), ritonavir (Norvir), atazanavir (Reyataz), or nelfinavir (Viracept);
An antifungal medication like itraconazole (Sporanox) or ketoconazole (Nizoral);
Carbamazepine (Tegretol), phenobarbital (Luminal), or phenytoin (Dilantin); or
Rifampin (Rifadin, Rimactane) or rifabutin (Mycobutin)

Explain all your recent and previous medical history in detail with your doctor before commencing therapy with any new medication. If you are using any herbal supplements or OTC, including vitamin pills, then communicate it to your doctor. Also, inform your doctor if you are using the following:
(Nitrolingual, Nitrostat, Nitro-Bid, Nitro-Dur, Deponit, Minitran, Transderm-Nitro), isosorbide dinitrate (Isordil, Dilatrate-SR, Sorbitrate), and isosorbide mononitrate (ISMO, Imdur, Monoket), or recreational drugs, for instance, amyl nitrate or nitrite ("poppers").

Avoid using Viagra if you have ever had an allergic reaction to it or if you have heart problems critical enough to make sexual activity unsafe. If you had a heart attack, stroke, or life-threatening heart variations within the past 6 months use it carefully. Also be cautious in case you have unstable blood pressure, heart failure, or weak angina.

In case you have cardiac symptoms like nausea, dizziness, and chest pain while sex stop taking Viagra.
In diseases like sickle cell anemia, multiple myeloma (a condition of the bone marrow), or leukemia where you might have long-lasting erection use Viagra carefully. In the case of genital problems or deformities such as Peyronies disease use Viagra cautiously. If an erection lasts for more than 4 hours, seek help quickly as it might lead to lasting sexual disorders.
If you are having conditions like bleeding disorder, a stomach ulcer, or the inherited eye condition known as retinitis pigmentosa use Viagra with care.

If you are awaiting a child or are planning to have a child in the near future, then discuss your doctor before using the drug to discuss any possible threats to the unborn baby.

If you are a nursing mother ask your doctor before using the drug as some drugs are passed in the breast milk and may enter the baby harmfully.