from the website MedlinePlus, with information from the National Institutes of Health:
"Some patients experienced a sudden loss of some or all of their vision after they took vardenafil or other medications that are similar to vardenafil. The vision loss was permanent in some cases. It is not known if the vision loss was caused by the medication. If you experience a sudden loss of vision while you are taking vardenafil, call your doctor immediately. Do not take any more doses of vardenafil or similar medications such as sildenafil (Viagra) or tadalafil (Cialis) until you talk to your doctor.
Some patients experienced a sudden decrease or loss of hearing after they took vardenafil or other medications that are similar to vardenafil. The hearing loss usually involved only one ear and may not get better. It is not known if the hearing loss was caused by the medication. If you experience a sudden loss of hearing, sometimes with ringing in the ears or dizziness, while you are taking vardenafil, call your doctor immediately. Do not take any more doses of vardenafil or similar medications such as sildenafil (Viagra) or tadalafil (Cialis) until you talk to your doctor."
do not take vardenafil if you are taking or have recently taken nitrates such as isosorbide dinitrate (Isordil), isosorbide mononitrate (Imdur, ISMO), and nitroglycerin (Nitro-BID, Nitro-Dur, Nitroquick, Nitrostat, others). Nitrates come as tablets, sublingual (under the tongue) tablets, sprays, patches, pastes, and ointments. Ask your doctor if you are not sure if any of your medications contain nitrates.
do not take street drugs containing nitrates such as amyl nitrate and butyl nitrate ('poppers') while taking vardenafil.
tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Be sure to mention any of the following: alpha blockers such as alfuzosin (Uroxatral), doxazosin (Cardura), prazosin (Minipress), tamsulosin (Flomax), and terazosin (Hytrin); amiodarone (Cordarone); antifungals such as fluconazole (Diflucan), griseofulvin (Fulvicin, Grifulvin, Gris-PEG), itraconazole (Sporanox), and ketoconazole (Nizoral); aprepitant (Emend);carbamazepine (Carbatrol, Epitol, Tegretol); cimetidine (Tagamet); clarithromycin (Biaxin); cyclosporine (Neoral, Sandimmune); danazol (Danocrine); delavirdine (Rescriptor); dexamethasone (Decadron, Dexpak); diltiazem (Cardizem, Dilacor, Tiazac); disopyramide (Norpace); efavirenz (Sustiva); erythromycin (E.E.S., E-Mycin, Erythrocin); fluoxetine (Prozac, Sarafem); fluvoxamine (Luvox); HIV protease inhibitors including atazanavir (Reyataz), indinavir (Crixivan), lopinavir (in Kaletra),nelfinavir (Viracept), ritonavir (Norvir, in Kaletra), and saquinavir (Fortovase, Invirase); isoniazid (INH, Nydrazid); lovastatin (Altocor, Mevacor); medications for high blood pressure or irregular heartbeat; metronidazole (Flagyl); nevirapine (Viramune); other medications or treatments for erectile dysfunction; nefazodone (Serzone); paroxetine (Paxil); phenobarbital; phenytoin (Dilantin, Phenytek);procainamide (Procanbid, Pronestyl); quinidine (Quinidex); rifabutin (Mycobutin); rifampin (Rifadin, Rimactane, in Rifamate); sertraline (Zoloft); sotalol (Betapace); troleandomycin (TAO); verapamil (Calan, Covera, Isoptin, Verelan); and zafirlukast (Accolate).Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
tell your doctor what herbal products you are taking, especially St. John's wort.
Herbal supplements are not always safe for everyone, especially if you are also taking pharmaceutical medications. Some have very serious drug interactions.
All the phosphodiesterase inhibitors, such as Viagra, Cialis, and Levitra, are heavy-duty vasodilators, and improperly used, they really can do serious permanent damage - most especially if someone doesn't know what kinds of other substances they interact with. Street drugs can make a deadly combination with ED drugs; of special note would be any stimulants (E, cocaine, amphetamines, or large doses of caffeine) which can cause heart attack/arrhythmias; or nitrates (poppers) which can cause the blood pressure to drop to nearly zero.