Sometimes a new and entirely different usecase is discovered for an already existing product. A good example of this is the pesticide Metaldehyde. This compound was originally developed as a solid fuel. It was only later discovered that it could also be used as a pesticide against snails.

Metaldehyde is used in snail pellets that also contain flour and molasses to make the pellet more attractive to snails. This concept was patented by Bayer AG and the patent has recently expired.

My question is whether it would also have been possible to patent metaldehyde itself as a slug pesticide.

2 Answers 2


I'm not a lawyer, but from what I know the answer is possibly yes. In fact this happens all the time in pharmaceuticals. A drug such as Humira, originally developed to address arthritis, is later found to have efficacy against other diseases. New patents are filed for and have been granted. The one question in the specific case you are asking about is whether the use against slugs is considered either novel or non-obvious over snails which are a related species. Without a lot more information, I can't answer that with any confidence.


It is a fine point but you aren’t patenting a known substance. You are patenting a method or process where some step requires the substance.

The statutory categories of patentable subject matter are — machine, article of manufacture, composition of matter, process and any improvement of one of those five things.

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