You know what they do for you. Here’s what they do to you.

Onset of Action
Viagra: about 60 minutes
Levitra: 30-45 minutes
Cialis: 45-75 minutes

Eating Beforehand
Viagra: 3 hours
Levitra: 3 hours
Cialis: anytime

Duration
Viagra: 4 hours
Vardenafil: 5 hours
Cialis: up to 36 hours

Nasal Congestion
Viagra: yes
Vardenafil: yes
Cialis: yes

Facial Flushing
Viagra: yes
Vardenafil: yes
Cialis: yes

Stomach Upset
Viagra: yes
Vardenafil: yes
Cialis: yes

Headache
Viagra: yes
Vardenafil: yes
Cialis: yes

Hazy Vision
Viagra: yes
Vardenafil: no
Cialis: no

Back Pain
Viagra: no
Vardenafil: no
Cialis: yes

General Achy Feeling
Viagra: no
Vardenafil: no
Cialis: yes

Heart Risk for Men Taking Nitrates
Viagra: yes
Vardenafil: yes
Cialis: yes

Medicines that can help produce an erection may be used to treat erection problems (erectile dysfunction) that are caused by blood vessel (vascular), hormonal, nervous system, or psychological problems. They also may be used along with counseling to treat erection problems that have psychological causes.

If erection problems could be caused by a prescribed medicine, it may be possible to change the dose or try another medicine. Do not change or stop taking any medicine without first talking with your health professional.
Medication Choices

Commonly used oral medicines include:
Phosphodiesterase-5 inhibitors (PDE-5 inhibitors) such as sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra).

Other medicines that may be used include:
Injected medications.
Intraurethral alprostadil (MUSE).

Hormones and other medicines may be prescribed for men who have low testosterone or high prolactin levels.

Caplan, a transient global amnesia expert, has seen many TGA patients, but only one man who had TGA after taking an ED drug.

The patient, a 51-year-old man with a history of hypertension and migraines, had played golf in the morning. After returning home with his girlfriend, he took Viagra.

“After 30 minutes, as he was about to engage in sexual intercourse, the patient reported that he ‘felt weird’… [and] could not remember that he had played golf that morning,” Caplan and colleagues wrote in Neurology’s Sept. 10, 2002, issue.

The man was hospitalized for a day. His memory gradually improved during that time, though he hadn’t regained his lost memories when he was discharged from the hospital.

Few other cases of transient global amnesia in men taking ED drugs have been published in medical journals. Those cases include a German man who experienced TGA after he apparently took Cialis, his doctors wrote in the International Journal of Impotence Research’s July/August 2005 issue.

None of the case reports confirm that ED drugs prompted transient global amnesia.

Cialis, Viagra: No Label Changes

The three erectile dysfunction drugs — Cialis, Levitra, and Viagra — belong to a class of drugs called phosphodiesterase type 5 (PDE-5) inhibitors. None has been shown to cause transient global amnesia.

Only Levitra is changing its label to note reports of transient global amnesia. The FDA tells WebMD it can’t comment on whether the makers of Cialis and Viagra have been asked to make similar label changes.

Pfizer makes Viagra. “We can’t really speculate whether the Viagra label will be updated, but we certainly do believe that the current label accurately reflects the safety and efficacy of Viagra,” Pfizer spokeswoman Jennifer Jacob tells WebMD in an email.

Eli Lilly & Co. makes Cialis. “Lilly typically doesn’t discuss potential label changes or regulatory action,” Stephanie Kenney-Andrzejewski, senior vice president for communications firm MS&L Global Health, tells WebMD on behalf of Lilly in an email. Kenney adds that “Cialis continues to be a generally well-tolerated and effective treatment for ED,” with a safety profile backed by clinical research in more than 16,000 patients and more than 11.5 million men worldwide who have been prescribed Cialis.