This is a very interesting question.
Dimethyl sulfoxide (DMSO) is a well-established chemical penetration enhancer that has been investigated as a carrier for topical (skin) insulin application. DMSO’s ability to disrupt the stratum corneum and increase skin permeability has made it a candidate for facilitating the transdermal delivery of large hydrophilic molecules such as insulin, which otherwise have poor passive skin absorption due to their size and polarity.
Recent preclinical studies have demonstrated that insulin-loaded colloidal carrier systems containing DMSO can achieve measurable transdermal insulin flux in animal models, with repeated administration resulting in significant reductions in blood glucose levels. DMSO’s role in these formulations is to enhance the penetration of insulin through the skin, either as a component of nano-sized drug delivery systems or in combination with other chemical enhancers and physical methods (e.g., iontophoresis, microneedles).
However, there may be important difference between topical application on the skin and the cornea, so let's look at topical ocular applications next.
Dimethyl sulfoxide as a carrier for insulin has been studied for ocular applications (in a controlled study in cats), but the results were considered disappointing. The study concluded that it does not result in effective absorption of insulin across ocular tissues. However, the aim of that study was to replace insulin injections with a non-invasive administration route for the purpose of maintaining the glycemic levels in diabetes patients. That's not our goal, so these "disappointing" study results likely do not apply to us.
In some good news from this study, the topical insulin-containing ophthalmic solutions formulated with DMSO did not cause ocular toxicity at the tested concentrations and dosing regimens.
DMSO is recognized for its ability to enhance ocular drug penetration and has been explored as a vehicle for various ophthalmic agents, with generally favorable safety profiles in experimental and clinical settings. It seems natural to test DMSO + insulin for human glaucoma. At this time I did not find any studies or clinical trials investigating this.
