The jury is still out on the effectiveness of nitroglycerin patches for Achilles tendonitis. However, nitroglycerin patch side effects are sufficiently low-risk that you could consider adding it to the tried-and-tested tendon loading approach if that alone isn’t working for you. This article looks at how these patches are thought to benefit tendon healing and summarises the results of the latest research on human subjects. Remember, if you need help with an Achilles injury, you're welcome to consult one of our team via video call.
The terms tendinitis, tendonitis, tendinosis, and tendinopathy mean the same thing for all practical purposes, and we use these interchangeably in most of our articles.
In this article:
We've also made a video about this:
The following terms refer to the same thing: Nitroglycerin, trinitroglycerin (TNG), nitro, glyceryl trinitrate (GTN), and 1,2,3-trinitroxypropane.
How nitroglycerin might help for Achilles tendonitis
When nitroglycerin reacts with oxygen, it forms nitric oxide. Nitric oxide is one of many substances found in injured tendons, including tendons with overuse injuries (like Achilles tendonitis) and traumatic injuries (like Achilles tears).
To understand whether nitric oxide is involved in tendon healing, researchers tested what happens when they suppress the production of nitric oxide in rats with injured tendons. Their results suggest that nitric oxide does play a part in tendon healing. When nitric oxide was suppressed, it led to weaker tissue.
In an attempt to understand how nitric oxide brings about these positive effects, they exposed human tendon cells (in a petri dish) to nitric oxide. This caused the cells to produce more collagen.
It is therefore thought that nitric oxide plays a role in the production of high-quality collagen, which is the main building block of tendons. So, the assumption is that if we can provide the injured tendon with more nitroglycerin, it may lead to increased nitrate oxide production, which may in turn enhance tendon healing in humans.
The problem with this assumption
We’ve seen with other research that just because something appears to work on rats or on human cells in a petri dish, it doesn’t necessarily mean that it will actually work in humans.
Also, it’s not really been shown that there is a lack of nitrate oxide in people with ongoing tendonitis. Therefore, adding more of the stuff might not make a difference, because we might already have optimal amounts.
So, what does the research on humans show?
Are nitroglycerin patches an effective treatment for tendonitis?
The short answer is: We don’t really know yet.
The research into the use of nitroglycerin patches for tendonitis is, well, pretty patchy. It has not produced strong results in favour of or against their use.
In 2019, Dimitris Challoumas, from the University of Glasgow, and his colleagues published a literature review of all the randomised controlled trials (RCTs – the gold standard in clinical research) that investigated the effectiveness of nitroglycerin patches as part of the treatment for tendonitis. They concluded that:
There was evidence for the effectiveness of nitroglycerin patches in the short and intermediate term treatment of tendinopathies (up to 6 months).
The use of topical nitroglycerin should be considered as an adjunct to loading programmes that don’t produce satisfactory resolution of symptoms.
But they also pointed out that: “…physicians should alert patients that large, well-designed RCTs and prospective cohort studies are warranted to provide convincing evidence on the effects of topical GTN in both acute and chronic tendinopathy, especially its long-term outcomes.” In other words, the quality of the available research is such that we cannot draw definite conclusions from the results.
A more recent (2022) meta-analysis of studies by Mikhail Saltychev and his colleagues at the University of Turku, in Finland, further highlights the lack of high-quality research.
When they pooled the results from the available research, they found: “There is no evidence that NTG is more effective to reduce pain in tendinopathy than placebo. The effects of NTG were insignificant or borderline significant (probably insignificant clinically) concerning rotator cuff tendinopathy, Achilles tendinopathy, patellar tendinopathy, and lateral epicondylitis.”
One of the problems with the current studies is that they all used different methods (different strength patches, duration of treatment, what other treatments it is combined with), which makes it difficult to compare results. Many of the studies also have serious flaws in their design, which means that you can’t really trust the results.
So, if the research can’t provide a clear answer, what should you do? Should you try nitroglycerin patches or rather avoid them? One of the things we at Treat My Achilles look at when advising patients is what risks a treatment poses.
Nitroglycerin patch side effects
The only side effects reported in the research associated with nitroglycerin patches are headaches and rashes. So, it appears to be relatively safe to use.
However, you may have specific health conditions or use other medication that may mean that these patches carry extra risk for you. So please discuss it with your doctor and don’t just go ahead and self-medicate.
What’s the verdict? Should you use nitro patches for tendonitis?
Nitroglycerin patches appear to carry little risk, and there is some evidence that it may help to reduce symptoms associated with tendonitis. We have also had some patients report positive outcomes from using it. So for now, we’re filing this under “treatments to try if you’re not making progress with your tendon-strengthening rehab programme”.
How we can help
Need help with your Achilles injury? You’re welcome to consult one of the team at TMA online via video call for an assessment of your injury and a tailored treatment plan.
We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine or at least 10 years' experience in the field. All of us have a wealth of experience working with athletes across a broad variety of sports and ranging from recreationally active people to professional athletes. You can meet the team here.
About the Author
Maryke Louw is a chartered physiotherapist with more than 20 years' experience and a Master’s Degree in Sports Injury Management. Follow her on LinkedIn and ResearchGate.