Interactions of Sildenafil: Drugs, Food, and Disease

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Written By Julie Ingram
interactions of sildenafil

Since FDA approval in 1998, Sildenafil has become a game-changer for men with Erectile Dysfunction (ED). It improves blood flow to the penis, which helps to maintain a firm erection.

Sildenafil, popularly known as Viagra, is FDA-approved and heavily tested. It is generally safe to use for most men and Assigned Males at Birth (AMAB) above 18. However, It can interact with certain medications and cause contraindications.

This article will discuss the interactions of Sildenafil with certain drugs, foods, and diseases. It will also discuss how to avoid interactions by taking some precautions.

Does Sildenafil Interact

Sildenafil (Viagra) can interact with various medications. However, it does not make it dangerous. 

Almost every drug interacts with certain other drugs. While taking any medication, you should always be cautious.

Sildenafil can interact with certain foods, drugs, diseases, and medical conditions and cause contraindications

Some interactions can cause side effects, while some will reduce effectiveness. 

Drug Interactions of Sildenafil

Consult a doctorSource: Syda_Productions
Consult a doctor before taking Sildenafil

Certain drugs that interact with Sildenafil are Nitrates, Alpha-blockers, other PDE5 inhibitors, Protease inhibitors, CYP3A4 inhibitors, etc.

If you experience any side effects while using Sildenafil stop using it immediately and talk to your doctor. 

Before taking Sildenafil, notify your doctor about all the medications you are taking.


Nitrates are medications for chest pain (Angina) and heart conditions. If you take Sildenafil with Nitrates, such as Nitroglycerin or Isosorbide Dinitrate, it can lead to a risky drop in blood pressure.

This drop in blood pressure can be dangerous and life-threatening. If you’re taking Nitrates, talk to your doctor before taking Sildenafil.


Alpha-blockers treat high blood pressure and Benign Prostatic Hyperplasia (BPH).

If you take Sildenafil with Alpha-blockers, it can cause a blood pressure drop which can cause fainting or dizziness.

Examples of Alpha-blockers include

  • Tamsulosin
  • Prazosin
  • Doxazosin

Protease Inhibitors

Protease inhibitors are a broad class of medications for treating viral infections such as HIV and Hepatitis C.

When protease inhibitors are taken with Sildenafil, they slow down the metabolism of the latter.

Since Sildenafil is not metabolized, it will accumulate in the body. This will increase levels of Sildenafil in the body. So, a max of 25 mg dosage of Sildenafil per 48 hours is advisable.

Your doctor will increase the dose depending on your health.

Other PDE5 inhibitors

Sildenafil is a member of a group of drugs called Phosphodiesterase type 5 (PDE5) inhibitors.

PDE5 inhibitors block PDE5, which helps relax blood vessels and lower blood pressure.

Since all PDE5 inhibitors work the same way, using other ED pills along with Sildenafil will drop the blood pressure to a dangerous level.

CYP3A4 inhibitors

Cytochrome P450 3A4 (CYP3A4) is an enzyme that breaks down drugs and toxins in the body. Taking Sildenafil when CYP3A4 is blocked will increase the level of Sildenafil in the body. This increased level can cause some side effects.

Depending on your health condition, your doctor might allow you to take Sildenafil at a lower dose.

Some examples of CYP3A4 inhibitors are

  • Clarithromycin
  • Erythromycin
  • Diltiazem
  • Itraconazole
  • Ketoconazole
  • Ritonavir
  • Verapamil
  • Goldenseal
  • Grapefruit
This is not a complete list of drugs that interact with Sildenafil. This article is for your information only. Never take Sildenafil without a doctor’s prescription.

Disease interactions of Sildenafil

Disease interactions of Sildenafil mean adverse effects of using Sildenafil with certain medical conditions.

Taking Sildenafil with some medical conditions can cause mild or severe side effects.

These medical conditions include cardiovascular diseases, liver disease, kidney disease, etc.

Cardiovascular diseases

Sildenafil dilates the blood vessels in the heart, brain, and penis. For people with heart conditions, this can put an excessive strain on the heart.

Anyone with heart disease or at high risk of heart attack should not take Sildenafil. It will increase your risk of experiencing shortness of breath, chest pain, or even a heart attack.

Liver or kidney disease

People with liver or kidney disease may need a lower dose of Sildenafil or avoid it altogether.

The liver helps to metabolize the drug, and the kidney helps to excrete it. If any of these are not working properly, Sildenafil will accumulate in the body and cause adverse effects.

Talk to your doctor about altering your doses.

Other health conditions

Some other health conditions can interact with Sildenafil. These health conditions include

  • Unstable Angina
  • Allergic reaction to Sildenafil
  • A penis deformity or Peyronie’s disease
  • Uncontrolled high blood pressure
  • Blood disorders like sickle cell Anemia or Leukemia
  • Stomach ulcers or a bleeding disorder like Hemophilia
  • Blood vessel conditions, such as Arrhythmia or Aortic Stenosis.
  • Retinitis Pigmentosa (a rare genetic eye disease)

Food interactions of Sildenafil

Alcohol addicted manSource: pixelshot
Avoiding alcohol

Food interactions with Sildenafil mean the impact of certain foods on the drug’s effectiveness or side effects. While using Sildenafil, be aware of these interactions to minimize potential risks.

Some notable food interactions include

  • Grapefruits – It is a potent inhibitor of intestinal CYP3A4. It will increase the level of Sildenafil in the body, which can cause side effects.
  • High-fat meal – Eating high-fat before taking Sildenafil will delay the drug’s absorption. It will reduce its effectiveness. You should take Sildenafil empty stomach or with a low-fat meal.
  • Alcohol – Drinking alcohol while using Sildenafil can intensify the side effects like headache, dizziness, and low blood pressure.
Remember to discuss your dietary habits and preferences with your healthcare provider. Professional advice is important before starting any new medication, including Sildenafil.

Why is it important to understand the medicine’s interactions

Understanding a medicine’s interaction is essential as it helps ensure the drug’s effectiveness and safety.

Awareness of possible interactions will help you make informed decisions.

Some reasons for understanding medicine’s interactions include the following:

  • Avoiding adverse side effects
  • Ensure effectiveness
  • Prevent toxicity


Sildenafil is a medication for treating ED. It was approved by the FDA in 1998. Sildenafil can interact with certain medications, foods, and medical conditions, causing side effects.

Being cautious and discussing your medications with a doctor is crucial. Sildenafil interacts with Nitrates, alpha-blockers, protease inhibitors, other PDE5 inhibitors, CYP3A4 inhibitors, etc. 

Disease interactions include cardiovascular diseases, liver or kidney disease, and other health conditions.

Food interactions involve grapefruit, high-fat meals, and alcohol.

Understanding these interactions ensures drug effectiveness, safety, and optimal use. It will also help you in making informed decisions about your treatment.

Beyond treating ED, Sildenafil is also used to address various medical issues. Delve into this article toExplore the Versatile Uses of Sildenafil in Medical Treatments

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  • Frequently Asked Questions

    Can Sildenafil be taken with over-the-counter painkillers?

    OTC painkillers, like Ibuprofen or Acetaminophen, can be taken safely with Sildenafil. But always consult your doctor before combining medications to avoid potential interactions.

    Is it safe to take Sildenafil with antidepressants?

    Yes, As per FDA, it is generally safe to take Sildenafil with antidepressants. But you should still consult your doctor before taking Sildenafil.

    Can I use Sildenafil with medications for Diabetes?

    Sildenafil is generally safe to use with Diabetes medications. However, it is essential to inform the doctor about diabetes medications. Your doctor will advise you on the proper dosage.

    Can I take Sildenafil if I am on blood thinners?

    Sildenafil is not known to cause significant interactions with blood thinners. It is essential to inform your doctor if you are taking anticoagulant medications.

    Is it safe to use Sildenafil with prostate medications?

    Some prostate medications, such as alpha-blockers, may interact with Sildenafil. It can cause a risky drop in blood pressure. Thus, it is advisable not to take prostate medications and Sildenafil together.