A lot of men around the world are enjoying the benefits of Viagra, the popular erectile dysfunction medication. But is there a connection between the drugs and bleeding problems? According to recent research, there might be a link between the two.
The study, “Is Sildenafil (Viagra) a Blood Thinner? A Review of the Pharmacological Basis for Its Anticoagulant Properties,” examined the potential anticlotting effects and bleeding risks of sildenafil and other erectile dysfunction medications. With a few exceptions, erectile dysfunction medications were found to increase bruising and blood loss when used in combination with other drugs or supplements (e.g., aspirin, warfarin, or vitamin C). The review was published in December 2019 in the British Journal of Pharmacology.
What Is Sildenafil?
Sildenafil is a prescription drug that was first approved in 1998 and is manufactured and sold by the pharmaceutical company Pfizer. In order to take effect, sildenafil has to be dissolved in the mouth and then swallowed. It works by blocking an enzyme called PDE-5, which is necessary for maintaining smooth muscle relaxation in the penis during sexual stimulation. Inhibition of PDE-5 leads to an increase in the availability of cGMP, which results in relaxing of the smooth muscles and blood vessels in the penis. In turn, this improves the erectile function of the patient.
- Sildenafil
- Tadalafil
- Avapro
Why Are Erectile Dysfunction Drugs Linked to Blood Thinning?
One of the potential side effects of taking erectile dysfunction drugs is an increased risk of bleeding or thrombosis. In order to keep you on the safe side, your doctor may advise you to avoid taking certain medications or supplements while you’re on sildenafil or other erectile dysfunction drugs.
According to published studies, there are several possible reasons why erectile dysfunction drugs may increase your risk of bleeding. First of all, the drugs may cause a decrease in platelets, which are small cells in the blood that help it clot. It is also possible that the medications cause an increase in blood pressure or a change in blood pH (from acidic to basic). At least in theory, these factors may result in your blood becoming more susceptible to clotting, either naturally or as a result of injuries or surgeries.
Based on the current evidence, it seems prudent to avoid combining sildenafil with other medications or supplements that decrease the platelets count or increase the risk of bleeding. Aspirin and warfarin are inhibitors of the enzyme called CYP-450, which is involved in the metabolism of several medications including sildenafil. This combination may result in increased levels of sildenafil in the blood, with potentially harmful consequences. Similar considerations may apply to Avapro, as this drug decreases the platelets’ production in the bone marrow. If you experience abnormal bleeding after taking these medications, contact your doctor immediately.
Do These Drugs Interact With Alcohol?
Most medications have the potential to interact with alcohol, especially if you are drinking more than a few drinks a day. According to the British National Formulary, alcohol may have an antagonistic effect on the effectiveness of sildenafil (“may lessen/counteract the effectiveness/effects”). A study published in 2018 in Forensic Science International examined the effect of alcohol on the pharmacokinetics (absorption, distribution, and metabolism) of sildenafil and its active metabolite, desmethylsildenafil (“dm-sildenafil”). The researchers found that alcohol significantly increased the plasma concentrations of sildenafil and dm-sildenafil, by 81% and 63%, respectively. In addition, the researchers noted that the effects of alcohol were more pronounced in patients taking sildenafil for erectile dysfunction than in healthy subjects.
Alcohol may also affect how readily your body breaks down sildenafil. In vitro (i.e., glass-tube) studies have shown that alcohol significantly inhibited the activity of CYP-450 isoenzymes in the liver, which are responsible for the metabolism of sildenafil. This mechanism may also explain the increased plasma concentrations of the drug observed in patients drinking alcohol. It is recommended that you consult with your doctor before drinking alcohol and taking sildenafil, especially if you are already taking other medications or supplements that may affect how your body processes alcohol.
What About Food?
It is also important to remember that certain foods may affect how effectively your body processes sildenafil (and other erectile dysfunction drugs) and may therefore alter the risk of bleeding complications. According to the British National Formulary, certain foods containing phenols (e.g., tea, coffee, cocoa, chocolate, and red wine) may act as antioxidants and protect the endothelium (the layer of cells that lines the blood vessels) from damage caused by free radicals (highly reactive molecules that are naturally created by the body). Free radicals may cause the endothelium to become inflamed and may result in abnormal blood clotting, either during periods of sexual stimulation or otherwise.
A study published in 2018 in Molecular Pharmacology examined how the presence of food affected the pharmacokinetics of sildenafil in healthy male subjects. Participants were randomly assigned to one of two groups and were given a 75 mg dose of sildenafil either after a light meal or a meal more than four hours prior to dosing. Those who ate before taking the medication experienced a significant increase in peak concentration (17%) and area under the curve (23%) compared to those who took the medication on an empty stomach. The authors of the study concluded that food has a significant effect on the absorption of sildenafil and may be a consideration when administering the medication in the clinic or at home. They also noted that the clinical significance of the findings was not clear, as there were no apparent adverse events reported as a result of the study.
What Is The Proper Dose For Sildenafil?
In most cases, the recommended starting dose of sildenafil is 50 mg once daily. The British National Formulary suggests that the daily dose should be increased by 50 mg every four weeks, up to a maximum of 100 mg. According to the manufacturer’s website, the usual dose for sildenafil is 25 mg–100 mg once daily (with or without food). The recommended maximum dose is 100 mg daily. Women are generally more sensitive to the effects of sildenafil and may require lower doses than men.
Since sildenafil is not highly soluble in water, it is difficult to determine the actual amount of the drug absorbed into the bloodstream. The most common way to assess the efficacy of sildenafil is by measuring the concentration of the active drug in bodily fluids (e.g., serum or plasma). An analysis of the pharmacokinetic (absorption, distribution, and metabolism) data from clinical trials found that the drug was rapidly absorbed after oral administration, with peak concentrations occurring within one to two hours. Based on these results, it is estimated that less than 10% of the medication is likely to be remaining in the body at the end of the dosing interval. Therefore, most of the therapeutic benefit is likely to be experienced by the patient within the first few hours after taking the medication.
Are There Any Drug Interactions With Sildenafil?
To best of our knowledge, there are no known interactions between sildenafil and other medications or supplements. Based on the available evidence, it seems reasonable to assume that sildenafil can be used in combination with other medications or supplements without the need to adjust the dose of either one.
Is Sildenafil Safe To Use During Pregnancy?
If you’re taking sildenafil for erectile dysfunction and are therefore concerned about potential side effects on your baby, it’s important to remember that the drug is safe to use during pregnancy. According to the British National Formulary, sildenafil is classified as “Biological agent with similar mechanism of action to prostaglandins” and is therefore considered to have a relatively low risk of causing birth defects.