Cialis (tadalafil) is a highly-efficient PDE5 inhibitor intended for the treatment of erectile dysfunction in patients unable to get an erection and keep it for long enough to have sex. Cialis was approved by the FDA in the year 2003 and since then has been successfully used for the treatment of erectile dysfunction. Your dose depends on the way you respond to the treatment and is usually between 5 mg and 20 mg. Consult your doctor if you are taking any medications that increase the levels of Cialis in the blood. The following medications are known to do that: itraconazole, erythromycin, ketoconazole, indinavir and ritonavir, so make sure you do not take more than 10 mg of Cialis if you are taking the drugs mentioned above. Avoid eating grapefruit and drinking grapefruit juice as interference with Cialis and its effects is possible. If you experience any strange side effects and they appear to be bothersome report them to your health care provider. Sudden vision loss is one of the rare side effects thought to be associated with taking Cialis, although it is not established whether Cialis is the only reason for it. In many cases vision loss was experienced by patients with certain pre-exciting problems. Loss of hearing is another rare side effect that may be associated with taking Cialis. You need to be aware of other possible, but again - very rare - side effects that are theoretically possible. The following ones should be mentioned: chest pain, seizure, vision changes, fainting, irregular heartbeat, shortness of breath, swelling in your hands, ankles, or feet. However, in most cases only mild side effects occur, such as headache, memory problems, facial flushing, sore throat, muscle pain, stuffy nose, diarrhea, and an upset stomach. Take Cialis with a full glass of water about an hour before having sex. Do not take a double dose to make your treatment more efficient as it is not going to happen and can even lead to a number of dangerous symptoms of an overdose, including stuffy or runny nose, heartburn, flushing, priapism, back pain, headache, and indigestion. You may be started on the lowest dose first and it can later be increased to see which one is best for you. The lowest dosage that you benefit from and that does not cause serious or unpleasant side effects is considered to be the best one. Make sure your dose is adjusted by a qualified health care professional.