Outside of the scientific, literary and loving context, talking about the fluids resulting from the mating of species is unpleasant for most. However, the findings of a new paper on frog foam come just in time to break the taboos by revealing an important utility in the administration of drugs in humans.

Frog foam, the perfect refuge for the young after mating

During the rainy summer nights in the north of Trinidad, the forests are the scene of competitions, serenades and passionate mating sessions among the Túngara frogs (Engystomops pustulosus).

Túngara frog foam released after mating.

The result of their love affair is a thick foam that male and female beat with their hind legs. Inside it, the eggs resulting from fertilization reside, which are hidden from predators and bacteria, and protected from extreme temperatures and ultraviolet radiation.

Túngara frog foam is the ideal refuge for its eggs, not only for its ability to hide and protect them against harmful environmental agents; also due to the fact that it is particularly durable. It can withstand harsh tropical environments for more than a week.

Foam is a practical way to administer drugs

Leaving aside the wild world and locating ourselves in the civilized one, humans have managed to develop artificial foams with wide uses, including the clinical one. The production methods are very different, of course, but they have served the function of efficiently distributing certain doses of drugs indicated for different ailments or cosmetic purposes.

Until now, they have been deployed to deliver medications such as dermal, rectal, and vaginal antibiotics, as well as skin care products. The main reason is that it offers benefits more suited to the particular needs of the body’s largest organ compared to pills and injections.

The limitations of today’s medicinal foams

However, there are still latent difficulties. One of them is that, once the foam is distributed over large areas of skin, the drug foams collapse in hours and even minutes.

This not only limits its effectiveness, but also means more work and material expense by having to apply the drug frequently. The early collapse of medicinal foam also disrupts the healing process and exposes the skin to dangerous pathogens, and even promotes resistance.

The search for solutions has led scientists to the Túngara frog foam, which, as we have already said, is resistant and durable, two very important attributes in the medicinal drug production industry.

Valuable properties for the pharmaceutical industry

A team took the foam to its laboratory in Scotland to test its properties and evaluate its usefulness in the pharmaceutical industry to fill current gaps.

Túngara frog foam used for the administration of drugs in humans.
Frog foam used in the laboratory to evaluate its properties in the administration of drugs. Credit: Paul Hoskisson.

In the process, they studied its structure, composition, viscosity, and stability. Thus they discovered that natural foam is made up of densely packed bubbles called vesicles. By mixing a drug in it, they capture and retain its molecules while spreading them over large surface areas without immediately collapsing.

With the passage of time, the warm temperature and the decrease in the pH of human skin cause the vesicles to dissolve. This is how they begin to release the drug.

Frog foam capable of administering drugs for a long time

In this sense, it is convenient to discuss the results of tests with a common antibiotic, rifamycin. The researchers applied half the prescribed dose in the first 24 hours, but the release time was one week. This period, which almost coincides with the five to 14 days that the administration of this type of medication usually lasts, which exceeds the existing pharmaceutical foams.

Túngara Frog capable of producing a foam useful for administering drugs on human skin.
Rana Túngara. Credit: Paul Hoskisson.

“This is the first time that an amphibious foam has been used for drug delivery,” said microbial biochemist Paul Hoskisson, co-lead author of the study. In his view, frog foam has the potential to function as a comfortable and safe drug delivery vehicle for patients.

However, there are still limitations to overcome. Among them, the fact that the frogs will not be able to supply the numerous tests that would have to be done to verify the safety and effectiveness of their foam, much less commercial needs.

Therefore, part of the future research should focus on the key proteins that provide the valuable properties for medicine and produce them in large quantities. This should also be inexpensive.


Frog nest foams exhibit pharmaceutical foam-like properties. https://royalsocietypublishing.org/doi/10.1098/rsos.210048