If you’re taking Sildenafil for ED then there are some Viagra contraindications and interactions you should be aware of. 

Viagra 100 pill on grey and white tiled square

For many men, even those with diabetes or high blood pressure, Viagra can help to safely restore erections. But some health conditions could make Viagra unsuitable for you or increase the risk of side effects. 

Viagra interactions refer to a whole manner of medicines and non-medicines that could cause trouble for the user if taken alongside the ED drug. This can be standard prescribed medications, or even mixing Viagra and alcohol or weed. 

A full list of sildenafil warnings can be found in the patient leaflet included with your order. Always read the PIL before you commence a course of treatment. If anything gives you cause for concern you should contact the prescriber or your doctor. 

Is Viagra dangerous? 

For most men, Viagra is not dangerous. But for men with certain conditions, it can be. 

For the most part, if you use Viagra you probably won’t notice any side effects or, if you do, they will likely be mild in nature. 

Viagra can be particularly dangerous if taken by someone who is also taking nitrates or nitric oxide. This combination of drugs is not safe. You should make the prescriber aware if you’re currently taking, or have recently taken, this category of drugs. 

Viagra is a safe treatment that has undergone rigorous clinical trials. It has been used successfully by millions of men around the world. It’s important to remember that Viagra is a medication and is not for recreational use. You should not take Viagra if you don’t have ED. 

Page reviewed by:
Mr Craig Marsh
Mr Craig Marsh
Pharmacist Prescriber
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Last updated 23/08/2021

Sildenafil warnings 

How well you get on with Viagra can have a lot to do with other health conditions. You’ll want to know which health conditions usually raise a flag, what it means for your treatment and how you can stay healthy whilst still achieving good erections. 

One of the appealing aspects of sildenafil is that it comes in three dosages. This means that your prescriber can adjust the strength of your treatment to suit your needs. 

Most men start with the 50mg dosage. But each individual’s medical history can influence their starting dosage. 

On the one hand, if you notice mild side effects on 50mg but otherwise Viagra works well for you, then your prescriber could lower your dose to 25mg. 

On the other hand, if you feel your erections aren’t quite up to scratch on 50mg, and you haven’t experienced side effects, then your prescriber could increase your dose to the maximum 100mg. 

Diabetes and Viagra 

You’re more at risk of developing ED if you have diabetes[1]. ED can be caused by various physical factors linked to diabetes.  There is some good news though. Diabetics with ED can be successfully treated with Viagra or other PDE5 inhibitors. A clinical trial showed that close to 60% of diabetic participants with ED reported erection improvements when taking Sildenafil [2].  If you have diabetes and Viagra doesn’t help your erections then there are other options available, including non-oral alternatives such as injectables, creams and vacuum pumps. 

High blood pressure and Viagra

ED is commonly associated with men who have high blood pressure[2]. The hardening of blood vessels can prevent a good supply of blood from reaching the penis, in turn making erections difficult to achieve. Another aspect of hypertension and ED is that sildenafil can interact with some of the active ingredients found in some BP drugs.  Viagra can be used with caution by those with hypertension but the prescriber may wish to keep a check on blood pressure levels.  All side effects experienced when using sildenafil should be reported to your doctor. If you notice any side effects such as a change in blood pressure, or a rapid heart beat then you should seek medical attention.

Does Viagra raise blood pressure? 

A change in blood pressure is an uncommon side effect linked to Viagra[3]. If you notice symptoms of a change in blood pressure, speak to your prescriber. 

Viagra’s active ingredient has been found to modestly lower blood pressure [4]. If you already have low blood pressure then your prescriber might suggest an alternative ED treatment. 

Taking Viagra after age 70

Prostate surgery can cause impotence[5]. However, Viagra and other PDE5 inhibitors can be successfully used as part of a penile rehab course.  It’s important to have a conversation with your doctor or specialist about regaining sexual function after surgery.  If oral medication does not work, there are other ED treatment options available to try. 

Taking Viagra after prostate removal

Viagra and Sildenafil are not the only PDE5 inhibitor pills used to treat ED. There are several other options available if you’re looking for the best Viagra alternative. 

So, whilst Sildenafil is a direct Viagra substitute there are other medications to try if, for example, you’ve noticed side effects when taking the popular ED pills. 

One of the strongest Viagra competitors is Cialis. When you pitch Cialis vs Viagra, you can see why some men prefer the pill that can last all weekend. Cialis can last up to 36 hours or there is an option to take a daily pill for those who prefer more spontaneous sex. 

Another strong contender when pitted against Viagra, is Levitra. The generic version of Levitra is vardenafil. Both can be classed as Viagra like pills as they fall into the PDE5i category. 

Sildenafil, tadalafil and vardenafil are the generic medications of their branded counterparts, and are often found to be cheaper. Different drugs work in different ways for each of the people that use it. It can depend on how your body metabolises the drug and your susceptibility to side effects. 

The only way to establish whether one drug works better than Viagra for you, is to try each of them. It goes without saying that this should be carried out under the guidance of your healthcare professional.

Sildenafil and Viagra contraindications

Not everyone can take Sildenafil or Viagra. Those with severe heart or liver problems, rare inherited eye conditions such as retinitis pigmentosa or those who have experienced loss of vision due to non-arteritic anterior ischaemic optic neuropathy (NAION) should be warned not to take Sildenafil.  There may be a link between sildenafil and permanent damage to the sight of those with inherited eye conditions[6] Other conditions to be considered when looking into Sildenafil as ED treatment include Peyronie’s Disease or deformity of the penis, sickle cell anaemia, leukaemia, multiple myeloma, stomach ulcers, haemophilia and other blood clotting conditions.  Where PDE5 inhibitors are not a suitable ED treatment due to a medical contraindication your doctor will be able to discuss alternative options. 

Can you take Viagra after a heart attack? 

How you recover after having a heart attack can alter when or if you can take Viagra. Once your doctor gives you the go ahead to engage in moderate physical activity then you reignite your sex life. However, should you need some help to achieve an erection, Viagra can help. 

The medication that you’re prescribed following a heart attack can sometimes interact with Viagra. We’ll talk more about Viagra and drug interactions further down the page. 

When you have a conversation with a doctor or prescriber about treatment for ED Make sure to inform the prescriber of your medical history. If you’re concerned about the effects of Viagra on heart strain, you should have a chat with your doctor. 

Can you take Viagra with a heart condition?

Taking Viagra when you have a heart condition can depend on a number of factors. This can include your age, how severe your condition is and what medications you are taking. The person prescribing your medication will take them into account. 

What drugs should not be taken with Viagra?

There are several drugs that should not be taken with Viagra. Nitrates (medicines prescribed for chest pain), nitric oxide donors such as amyl nitrate (also known as ‘poppers’) and Riociguat. 

If you are taking any of these medicines you must inform the prescribing clinician. They can let you know what other ED treatments might be more suitable for you.

Viagra and nitrates for chest pain

Sildenafil and nitrates should not be taken together because they can both lower blood pressure. The potential hypotensive effects of each medicine when combined could result in significant life threatening side effects[7]. If you have been prescribed nitrates for chest pain or another condition then you need to speak to your doctor about taking Viagra.

Viagra and drugs for pulmonary hypertension

Sildenafil, the active ingredient in Viagra, is also used to treat pulmonary hypertension. Therefore if you are already taking drugs to treat pulmonary hypertension then there could be a cumulative effect which could cause dangerous side effects. 

Viagra and Riociguat

Riociguat is used to treat pulmonary arterial hypertension (high blood pressure in the lungs) and chronic thromboembolic pulmonary hypertension (high blood pressure caused by blood clots in the lungs). If taken alongside a PDE5 inhibitor such as Viagra, the hypotensive effects of the medicine can increase. This means that your blood pressure could drop too low. 

In order to avoid dangerous interactions, be sure to let your prescriber know what medications you are taking. 

What drugs can cause possible Sildenafil interactions?

There are some drugs that can potentially lead to interactions when taken with Viagra. The decision to take these drugs at the same time can be evaluated by the prescriber on an individual basis, as doing so may require monitoring. 

Depending on the medication you are taking, your doctor may suggest a lower starting dose of Viagra to see how you get along. 

Blood pressure medicines and Viagra

Your prescriber needs to know if you’re taking medication for blood pressure. This is important across the board, no matter what type of blood pressure treatment you’re using.  The category of medication called Alpha-blockers is used to treat hypertension and enlarged prostate. Alpha-blockers can interact with Viagra and thereby lead to side effects.  If you take alpha-blockers and have ED then it’s normal for Viagra (or other PDE5 inhibitors) to only be prescribed when your blood pressure is well-controlled[8]. Also, don’t be surprised if your doctor suggests starting on the 25mg dosage. 

Lisinopril and Viagra

Lisinopril belongs to the group of medicines known as ACE inhibitors and is another treatment for high blood pressure. It can be taken alongside PDE5 inhibitors such as Viagra but it may require monitoring. 

If you experience side effects indicating low blood pressure, for example feeling faint, dizzy or a rapid pulse or heart rate then speak to your doctor. These side effects are more likely to occur when you first start taking sildenafil. 

Losartan and Viagra 

Losartan can help treat high blood pressure and heart failure. It is an angiotensin-II receptor antagonist. Sildenafil can increase how much Losartan lowers blood pressure. They can be taken together but extra care may be required. 

Amlodipine and Viagra 

Amlodipine is another blood pressure lowering drug. Therefore caution should be taken when using alongside Viagra. 

Terazosin and Viagra 

Terazosin is an alpha-blocker. Therefore if it is taken with Viagra you should be aware of possible low blood pressure side effects.

Can Viagra be taken with beta blockers?

Some blood pressure drugs such as beta blockers may be linked to ED[9]. Therefore if you are taking them and notice ED symptoms you should speak to your doctor. There are different types of treatments for hypertension and it may be worth exploring them, guided by your doctor, to see if the problem resolves.

Antidepressants and Viagra

Antidepressant medications can cause ED for some men[10]. However, mental health and the ability to obtain an erection can also be linked. As with all medications, and as we’ve mentioned many times before, you should let your doctor know if you’re taking antidepressants. This may influence the approach taken to address your ED. 

Sertraline and Viagra

Sertraline is a selective serotonin reuptake inhibitor (SSRI) used to treat depression. SSRIs can be linked to ED, the frequency of which is estimated between 25-73%[11]. If you are taking SSRIs you should inform your doctor if you notice ED symptoms. Don’t stop taking your medication or make any change until you’ve discussed this with your healthcare provider. Sertraline and Viagra can be used together but may require monitoring.

Can you take Viagra at the same time as other ED treatments?

Viagra is a great choice of treatment for many men experiencing ED. However, for some it might not work as well as they’d hoped. This could lead to looking for added-extras to top up their erection response. Doing so could be dangerous and is not recommended. 

Can you take Cialis and Viagra together?

Mixing Cialis and Viagra is a bad idea. Doing so could be dangerous and increase the likelihood of side effects occurring, including priapism, which can cause serious damage to the cells in your penis. It’s also worth noting that both drugs, although containing different active ingredients, work in the same way. Therefore combining two PDE5 inhibitors won’t increase the strength of your erection. 

So, if you’re even considering taking Cialis and Viagra together, because your current treatment isn’t working out for you, then speaking to your doctor should be the first step. There are lots of ED treatment options out there and most ED cases can be successfully treated without risking those all important penile cells. 

Mixing herbal remedies with Sildenafil

You should include any herbal remedies when you list your medications to your prescriber. This allows them to check whether the combination is safe for you to take. For example the herbal remedy St John’s wort may make sildenafil less effective. 

Can you drink alcohol and take Viagra at the same time?

Drinking alcohol on the same day as taking Viagra is not likely to cause any interactions. However, it’s probably best to keep your drinking within moderation as too much alcohol can impair your ability to obtain an erection, even with Viagra there to bolster your performance. 

Taking recreational drugs and Viagra

Recreational drugs come with their own extensive list of potential problems, as you never truly know what it is that you’re putting in your body. If you then start mixing them with other medication, such as Viagra, you could be creating a recipe for disaster. 

It’s also quite possible for recreational drugs to be linked to the cause of ED. The side effects from taking recreational drugs such as cocaine could mean that getting an erection is more difficult. 

The ingredient amyl nitrate, found in ‘poppers’, when combined with Viagra can cause a dangerous drop in blood pressure. As we’ve already touched on, sildenafil and nitrates should never be taken together. 

Viagra and weed (or cannabis) should be given a wide berth too. Anecdotally cannabis is linked to poor sexual health function. However, due to a lack of scientific research into the area it is difficult to pin down the exact relationship between weed and ED. This can also be said of the potential interactions between cannabis and Viagra. Those who use weed for recreational purposes should not take Viagra as how the two will interact with one another is not fully understood. 

If you’re concerned about your recreational drug use you can speak to your GP. You can also use the Frank website to find a local drug treatment service. 

How to avoid sildenafil drug interactions

The list of potential drug interactions when taking sildenafil may seem a little daunting. But there is a simple way of keeping interactions at bay. And that’s being open and honest when speaking to your prescriber about your medication. Give them the full picture and they’ll be able to make informed decisions about your treatment. 

What you can do to minimise any potential interactions is read the patient information leaflet provided with your treatment and take your medication as directed by the prescriber. If you do notice any side effects when taking Viagra then report them back to your doctor to see if any adjustments can be made. 


[1] Association between erectile dysfunction and cardiovascular risk in individuals with type-2 diabetes without overt cardiovascular disease. Meena et al. (2009) 

[2] Viagra. Summary of Product Characteristics. Electronic Medicines Compendium (eMC) (2020) 

[3] Management of erectile dysfunction in hypertension: Tips and tricks. Viigimaa et al. (2014) 

[4] Use of Sildenafil (Viagra) in Patients With Cardiovascular Disease. Cheitlin et al. (1999),greater%20drops%20in%20blood%20pressure

[5] Erections after prostatectomy surgery: does Viagra still work? Lamb et al. (2019) 

[6] Sildenafil alters retinal function in mouse carriers of Retinitis Pigmentosa. Nivison-Smith et al. (2014) 

[7] Sildenafil (Viagra) and the heart. Hassan Chamsi Pasha. (2001) 

[8] Cardiovascular safety of sildenafil citrate (Viagra): an updated perspective. Jackson et al. (2006) 

[9] Blood pressure drugs and ED: what you need to know. Matthew Solan. 

[10] When an SSRI medication impacts your sex life. Julie Corliss. (2019) 

[11] Antidepressant-associated sexual dysfunction: impact, effects, and treatment. Higgin et al. (2010).