Sildenafil, best known under the brand name Viagra, is an FDA-approved medication used to treat both erectile dysfunction (ED) and pulmonary arterial hypertension (PAH)—but the route of administration matters.
- For ED: Sildenafil is approved only in oral tablet form.
- For PAH: A separate formulation, intravenous (IV) sildenafil, is approved under the brand name Revatio and used strictly under medical supervision in hospital or clinical settings.
Because both forms exist, some may wonder whether injecting sildenafil or crushing the tablets could make it work faster. The answer is no. Injecting sildenafil or altering the tablets is unsafe, not clinically tested, and not supported by medical evidence.
Table of Contents
How Does Sildenafil Work?
The sexual response in men has three phases: interest/libido, the ability to obtain and sustain an erection, Sildenafil is a phosphodiesterase-5 (PDE5) inhibitor that enhances nitric oxide–mediated vasodilation in the penile tissue, improving blood flow during sexual arousal.
- Sexual stimulation releases nitric oxide in penile blood vessels.
- Nitric oxide increases cyclic guanosine monophosphate (cGMP), causing smooth-muscle relaxation and increased blood flow.
- PDE5 breaks down cGMP, ending the erection.
- Sildenafil blocks PDE5, allowing cGMP to remain elevated and the erection to last longer.
Sildenafil works only in the presence of sexual stimulation. Men with vascular or metabolic damage (e.g., from hypertension, diabetes, or smoking) may find reduced effectiveness.
How Do You Take Sildenafil?
Sildenafil tablets come in 25 mg, 50 mg, and 100 mg strengths.
- Take about 30–60 minutes before sexual activity (up to 4 hours before).
- Effects last 4–5 hours.
- Avoid high-fat meals or grapefruit products, which can delay absorption.
- Do not combine sildenafil with other PDE5 inhibitors or nitrates.
- Do not exceed one dose per 24 hours.
What Are Sildenafil’s Side Effects?
Do not take sildenafil with nitrates, guanylate cyclase stimulators such as riociguat, or other PDE-5 inhibitors.
Potential side effects and the percentage of people experiencing these side effects in clinical trials include:
- headache (15.8%)
- facial flushing (10.5%)
- upset stomach (6.5%)
- nasal congestion (4.2%)
- flu syndrome (3.3%)
- urinary tract infection (3.1%)
- abnormal vision (2.7%)
- diarrhea (2.6%)
- dizziness(2.2%)
- rash (2.2%)
- back pain (2.2%)
- joint aches (2.0)
- other side effects reported less than 2%
Since sildenafil sustains an erection by blocking PDE-5, there is the potential for priapism, a prolonged, painful erection. Priapism is when blood fills the spaces in the penis and causes an erection but prevents the blood vessels from draining over time. When blood sits in the penis and fresh blood cannot enter it, oxygen levels may fall, causing tissue damage. Before taking sildenafil, talk to your doctor about the steps you should take if you experience priapism.
Sildenafil can also cause decreased blood flow to the optic nerve in the eye, causing vision changes and, in rare cases, sudden loss of vision. It is not clear whether sildenafil caused vision loss. People who experienced vision loss after taking sildenafil commonly also had heart disease, diabetes, high blood pressure, or high cholesterol or were smokers over the age of fifty.
Sildenafil may cause dizziness and altered vision. See how the medication affects you before driving or operating heavy equipment. Alcohol can lower blood pressure, worsening symptoms.
Will Sildenafil Work Faster Or Better If You Crush The Tablets?
To answer this question, researchers compared the bioequivalence of sildenafil tablets in pill form (not sustained release) with crushed sildenafil tablets in applesauce and an oral suspension. All three formulations worked the same, suggesting that there is no benefit to crushing a sildenafil tablet.1 The participants in this study were all fasting. A high-fat diet can slow sildenafil absorption. More research is needed to see if crushing sildenafil will mitigate the absorption delay.
Can You Dissolve Sildenafil (Viagra) In Water?
Researchers compared sildenafil as a suspension and an oral pill and measured plasma drug concentration. Both forms gave a similar drug concentration, suggesting that dissolving sildenafil in water might be an option for men who cannot swallow pills.1 This research was done under controlled circumstances with fasting volunteers. Some medication may be lost in the container after dissolving, causing a decreased dose. If you can swallow tablets, that is the preferred and tested way to take sildenafil.
Can You Use Viagra Intravenously?
Sildenafil injection (Revatio) is indicated to treat pulmonary hypertension (high blood pressure in the lungs) to improve exercise capacity. Revatio is administered as an intravenous bolus three times daily. According to drugs.com, a 10 mg injection dose is predicted to have the same effect as a 20 mg oral dose. The intravenous form is commonly given until pulmonary hypertension is stabilized. Viagra should never be given intravenously at home unless under the close supervision of a medical professional.
Can You Inject Sildenafil?
Intercavernous injections (penile injections) are a highly effective treatment for ED. However, sildenafil does not come in an injectable form, and it has not been tested for safety and efficacy in this form.
Sildenafil is a very effective oral treatment for ED.2 If you would prefer an injectable ED medication, consider Trimix. Trimix injectables are a combination of three different medications—phentolamine, papaverine, and alprostadil—that synergistically increase blood flow into the penis.Â
Bimix is a combination of papaverine and phentolamine.
Quadmix combines papaverine, phentolamine, prostaglandin E1, and atropine.Â
Sildenafil is an effective ED treatment for many men. The preferred dosage method is swallowing the pill. There does not seem to be advantages to crushing the pill, and it’s dangerous for your health to inject the oral form of sildenafil. In order to buy sildenafil, talk to a Treatment Specialist at Invigor Medical.
Frequently Asked Questions
Is there an injectable form of Viagra?
Yes, sildenafil, the active ingredient in Viagra, is available in injectable form. It’s called Revatio and is typically used for treating pulmonary arterial hypertension (PAH) rather than erectile dysfunction.
What is the price of sildenafil injection?
The cost of sildenafil injection can vary depending on factors such as the manufacturer, dosage strength, and where it’s purchased. Prices can range from relatively affordable to more expensive, especially for brand-name versions.
How do you inject sildenafil?
Sildenafil injection is administered intravenously (IV) or as a bolus injection into a vein. It’s important for healthcare professionals to handle and administer it according to prescribed guidelines to ensure safety and efficacy.
Can you put sildenafil in water?
Sildenafil is typically not mixed with water for administration. Instead, it’s administered as a solution directly into the bloodstream through an IV. Mixing it with water may affect its stability and effectiveness. Always follow the instructions provided by a healthcare professional.
