Cialis and Grapefruit Enhance: Is There an Interaction?

Cialis is one of the most well-known medications for treating erectile dysfunction, right up there with Viagra and Stendra.

Approved for use by the FDA, Cialis works through its active ingredient — tadalafil to reduce the dissatisfaction, stress, and anxiety that comes with a sex life affected by erectile difficulties. This oral medication has also been used in the treatment of benign prostatic hyperplasia, otherwise known as prostate enlargement.

However, despite the many benefits attributed to Cialis, there is a chance that its effectiveness may be affected by an unlikely source: grapefruit.

In this piece, we’ll be examining the way Cialis works to manage erectile dysfunction, how effective it is at this role, and if grapefruit can truly affect its performance.

How Does Cialis Work?

As mentioned, Cialis helps with the management of erectile dysfunction, a very common condition that affects 30 million men in the United States alone.

In addition to nerve supply, and hormonal issues, erectile dysfunction may be affected by the poor flow of blood to the penis — this is where Cialis, through its active ingredient — tadalafil comes in.

An erection occurs through processes regulated by hormones, blood vessels, nerves, and muscles.

The erection typically begins with stimulation that occurs by touch, sight, hearing, or the imagination. 

This prompts the release of nitric oxide, a gas that stimulates blood flow into the spongy tissue of the penis. 

Blood flows into these tissues when the penile muscles are relaxed, a process made possible when nitric oxide encourages the production of cyclic guanosine monophosphate (cGMP). 

Ideally, cGMP accumulates to allow the smooth muscles in the penis to relax and cause an erection to form, however, PDE-5, an enzyme found in these muscles may degrade this compound and prevent its accumulation. 

This prevents the blood vessels in the penis from relaxing and opening up properly.

As a PDE-5 inhibitor, Cialis prevents this degradation by binding to PDE-5. This causes an increased accumulation of cGMP which causes increased blood flow to the penis, which, by extension promotes stronger, long-lasting erections.

How Effective Is Cialis?

To produce the best results from your sexual encounters, Cialis is available as an on-demand or everyday medication.

Every day doses are found in the 2.5 mg and 5mg ranges. Because Cialis lasts longer in the body (up to 36 hours in some cases) these dosages can be administered at a specific time during the day, and allow for spontaneous sex for the rest of it. 

This releases you from having to plan your medication ahead of time. 

A heavier dose like 10mg is usually the starting dosage for this medication. This dose can be increased to 20mg if the response is low to the 10mg dosage. 

These Cialis doses are on-demand, meaning rather than taking them every day, they are reserved only for days you are certain of sex.  But how do these doses hold up in treating erectile dysfunction?

In an eight-week study carried out on 127 men, the effectiveness of a daily dose of tadalafil 5mg was tested. Its safety for the cardiovascular system was also examined.

By the end of the study, although seven participants reported adverse effects, it was resolved that 5mg of tadalafil could be effective in improving erectile function with minimal adverse effects on the cardiovascular system.

Another study confirmed the effectiveness of a daily dose of tadalafil 5mg and demonstrated the effects of the daily 2.5mg dose in treating erectile dysfunction.

This study ran for 24 weeks and divided participants into groups that were assigned the two dosages of tadalafil and placebo treatments respectively.

At the end of 24 weeks, tadalafil was found to be well-tolerated and effective in treating erectile difficulties. However, 5mg was found to have stronger effects in managing erectile dysfunction.

Cialis has also been proven safe for long-term use, as confirmed by this study which found that tadalafil at 5mg, 10mg or 20mg taken as needed up to once daily posed a low risk to the health and was well tolerated.

What Are the Effects of Grapefruit on Cialis?

Let's put it like this, if you were thinking of washing your dose of Cialis down with a swig of grapefruit, maybe swap it for a glass of water.

Grapefruit juice can cause a drug interaction when taken with certain drugs, and Cialis is one of them. To explain, a drug interaction occurs when the effects of a medication are altered when another substance is taken. 

These effects may enhance the benefits or reduce the effectiveness of the drug. In some cases, it may cause toxicity.

In the case of grapefruit and Cialis, this liquid or the fruit itself produces an unwanted effect. In its role as a PDE-5 inhibitor, Cialis acts as a vasodilator to promote the flow of blood to the penis. When combined with grapefruit, this effect can cause a serious increase in blood flow around the body, especially when combined with a nitrate.

This is because grapefruit can increase the amount of Cialis in your body. It can achieve this by preventing presystemic metabolism — a process where the concentration of Cialis is reduced before it reaches the body circulation. This causes higher amounts of Cialis in the body, which can persist for 24 hours after the juice has been taken.

But this effect isn't limited to just Cialis. Grapefruit has been known to cause similar effects when taken with antihypertensives, as well as other PDE-5 inhibitors like sildenafil (generic Viagra) and vardenafil. It has even been known to cause strokes when taken with certain migraine medication.

For the best results, avoid consuming grapefruit around the time you intend to use Cialis.

Other Cialis Interactions

In addition to grapefruit, the following substances may cause an increase in serum concentration of Cialis:

  • Antifungal medication Ketoconazole
  • The antibiotic erythromycin
  • Protease inhibitors which are used to treat HIV/AIDS, as well as hepatitis C

In contrast, when using drugs like rifampin (antibiotic), carbamazepine (anti-epileptic drug), phenytoin(anti-seizure medication) and phenobarbital (anti-seizure, anti-anziety treatment) larger doses of tadalafil are required to achieve an erection.

The Long and Short...

Cialis is high up on the recommendation list when it comes to managing erectile dysfunction.

However, its mechanism of action which causes an increase in blood flow to the penis may affect other body parts, especially when combined with substances like grapefruit.

In addition to grapefruit, when taking Cialis, either as a daily or on-demand medication, care has to be taken to avoid administering it with certain antibiotics and anti-seizure drugs.

Learn more about the effects Cialis can have on your body by speaking with a qualified healthcare provider.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.