Objective: To evaluate evidence on the effectiveness of topical nitroglycerin (NTG) in treating tendinopathies.
Data sources: Systematic searches were conducted on ScienceDirect, Scirus, Highwire Press Stanford University, PubMed Central, Directory of Open Access Journals, Free Medical Journals, Free Full Text, Bioline International, Findarticles, BioMed Central, IndMed, OpenMD, QMed, Geneva Foundation for Medical Education and Research, Scientific Electronic Library Online, eMedicine/Medscape/Medline, Biomedical E-journals, Current Contents Connect, Journal of Medical Internet Research, Cochrane, Turning Research Into Practice, Ovid, and EBSCO databases. There were no restrictions regarding the language of publication.
Study selection: All clinical controlled trials or randomized controlled trials (RCTs) evaluating the effects of NTG for patients with acute, subacute, or chronic tendinopathies, whether the said intervention was placebo-controlled or controlled against a comparator intervention, were considered for inclusion.
Data extraction: A reviewer extracted data from included studies using a data extraction form by the Joanna Briggs Institute.
Data synthesis: Methodologic quality of studies was assessed by 2 independent reviewers through a critical appraisal form by the Alberta Heritage Foundation. Qualitative analyses of data were done using a rating system devised by Van Tulder and colleagues. Where possible, meta-analyses of data were performed. Seven clinically relevant and high-quality RCTs involving 446 subjects were identified and included in this review. Meta-analysis showed that NTG has a positive effect in pain reduction during activities of daily living in chronic tendinopathies, with an odds ratio of 4.44 (95% confidence interval [CI], 2.34-8.40), and in both acute and chronic phases combined, with an odds ratio of 4.86 (95% CI, 2.62-9.02). There is also qualitative, strong (Level 1) evidence that NTG is effective in enhancing tendon forces in the chronic phase. There is limited and/or conflicting evidence (Level 3) for other outcomes in the chronic phase and all outcomes in the acute phase. There is a significant between-group difference between NTG and control in the incidence of headache, with an odds ratio of 1.73 (95% CI, 1.01-2.97). No significant difference was observed in the occurrence of contact dermatitis, with an odds ratio of 2.12 (95% CI, .89-5.02).
Conclusions: In chronic tendinopathies, there is strong evidence for NTG in relieving pain during activities of daily living, and increasing tendon strength. Further studies are needed to explore the role of this promising intervention in all phases of tendinopathies.