Cialis, also known by its generic name, tadalafil, is an oral drug for the treatment of erectile dysfunction. It belongs to the class of drugs known as phosphodiesterase, or PDE, 5 inhibitors and works by relaxing the muscles, which allows blood to flow to the penis causing an erection. It may be taken once daily or on an as-needed basis. Cialis is not suitable for all men including those with uncontrolled hypertension, stroke or heart failure. There are a number of alternatives to Cialis.

Viagra, also known as sidenafil, belongs to the same class of drugs as Cialis and works in a similar way. According to Drugs.com, Viagra is an oral drug and is usually taken 30 minutes to 1 hour before sex. The effects of Viagra last about four hours. It should not be taken more than once a day. Like Cialis, Viagra is not suitable for certain men including those with heart problems and men taking nitrates for chest pain. Common side effects may include an upset stomach, headache and memory problems. Men who experience sudden vision loss, an irregular heartbeat or chest pain should immediately discontinue use and contact a doctor.

Levitra, known also by its generic name, vardenafil, is another PDE5 inhibitor for the treatment of impotence. It is an oral drug usually taken one hour before sexual activity, and its effects last about five hours. Like Viagra, it should only be taken once per day. It is contraindicated for men using nitrates for chest pain and men with heart problems. Side effects may include flu-like symptoms, headache, a stuffy nose and heartburn. Like Viagra, men who experience vision problems, chest pain or breathing problems should discontinue use and contact a doctor.

A vasodilator drug known as alprostadil can be injected into the penis or taken as a penis suppository. The alprostadil injection is self-administered and usually triggers an erection in 5 to 20 minutes. The needle is very fine, so does not usually cause pain, but minor bleeding may occur. The erection should last for no longer than one hour. The alprostadil suppository is inserted via a specially designed applicator which delivers the drug two inches into the penis. This method of administration can be painful and may cause bleeding of the urethra, notes Mayoclinic.com.

Alternative medicines may be used for erectile dysfunction, but Mayoclinic.com notes that their safety and efficacy are not fully known. Examples of alternative medicines that may help include Korean red ginseng, yohimbine, ginkgo biloba and dehydroepiandrosterone. Since these may interact with conventional erectile dysfunction treatments, patients considering using them should speak to a doctor first.