
Oral medications that treat erectile dysfunction (ED) are classified as phosphodiesterase type 5 (PDE5) inhibitors. They work by increasing blood flow to the penis so that a man can have a firm enough erection for sex. Sildenafil (Viagra – both name-brand and generic), avanafil (Stendra/Spedra), tadalafil (Cialis – both name-brand and generic), and vardenafil (Levitra) are all PDE5 inhibitors.
For some men, certain types and quantities of foods, as well as alcoholic beverages, can interfere with the way these drugs work.

Some men find that ED drugs, particularly Viagra and Levitra, work better when taken on an empty stomach. If the pills are taken too soon after eating (especially a big meal), it can take longer for them to work, and their effect can be reduced.
Also, men might see less effect if they take the drugs after eating a fatty meal.
Keep in mind that ED drugs do not produce an erection automatically. A man still needs sexual stimulation for them to work.

Excessive alcohol intake may reduce the effectiveness of ED drugs, too. Alcohol can impair erections in general, even in men without ED. If a man already has poor erections and needs ED medication, then adding alcohol to the mix can make it harder for that medication to do its job.
This doesn’t mean that a man can’t have a glass of wine with dinner before sexual activity. But if it seems that his ED drug isn’t working, he might want to reconsider how much alcohol he drinks.

Men who are unsure about the effectiveness of their ED drugs should re-read the instructions that came with their drug package and make sure they are taking the drugs correctly. They should also ask their doctor or pharmacist about their particular medication.
While oral drugs can be an effective treatment for ED, they don’t always work for all men. In addition, men who take nitrates should not take ED drugs. Fortunately, there are other treatment options, including self-injections, suppositories, and vacuum devices. (Click here for more information about ED, its causes, and treatment.)
Resources
Cleveland Clinic
Ulchaker, James, MD
“Can What You Eat or Drink Cause Erectile Dysfunction?”
(November 30, 2017)
https://health.clevelandclinic.org/can-what-you-eat-or-drink-cause-erectile-dysfunction/
Eli Lilly and Company
“Cialis – Patient Package Insert”
(Revision date: May 2017)
http://uspl.lilly.com/cialis/cialis.html#ppi
EverydayHealth.com
Iliades, Chris, MD
“Why Boozing Can Be Bad for Your Sex Life”
(Last updated: January 4, 2012)
https://www.everydayhealth.com/erectile-dysfunction/why-boozing-can-be-bad-for-your-sex-life.aspx
GSKSource.com (GlaxoSmithKline)
“Levitra – Patient Information”
(Revision date: August 2017)
https://gsksource.com/pharma/content/dam/GlaxoSmithKline/US/en/Brands/LEVITRA/pdf/LEVITRA_PI.PDF#page=24
Harvard Medical School
“Which drug for erectile dysfunction?”
(May 2014)
https://www.health.harvard.edu/mens-health/which-drug-for-erectile-dysfunction
Healthline.com
Morris, Susan York and Cathie Ericson
“Viagra, ED, and Alcoholic Drinks”
(August 3, 2016)
https://www.healthline.com/health/erectile-dysfunction/viagra-alcohol
MensHealth.com
Sgobba, Christa
“6 Reasons Your ED Drug Isn’t Working”
(March 13, 2016)
https://www.menshealth.com/health/common-erectile-dysfunction-medication-mistakes
Sexual Medicine Society of North America
“Alcohol and Sex”
(January 27, 2015)
http://www.sexhealthmatters.org/sex-health-blog/alcohol-and-sex
Stendra.com
“Patient Information Stendra”
https://www.stendra.com/patient-information-stendra/
UCSF Health (University of California San Francisco)
“Oral Medications for Erectile Dysfunction”
https://www.ucsfhealth.org/education/oral_medications_for_erectile_dysfunction/
Viagra.com (Pfizer)
“Tips for taking Viagra”
https://www.viagra.com/taking/tips-for-taking-viagra