When is a hydrosol not a hydrosol? When it is formed within the body, according to a recent court judgment on Novartis's claimed patent infringement against generic drugs company Eon. Novartis Pharmaceuticals has used its patented hydrosol formulation to administer the poorly soluble immunosuppressant drug cyclosporin in a readily absorbable aqueous form. Novartis's US patent 5,389,382 explains that a hydrosol formulation can be prepared by dissolving the drug in a water-miscible solvent and then adding a comparatively large amount of water to that solution. The result is an aqueous dispersion of very small solid drug particles that are more readily absorbed.

Eon makes capsules that contain cyclosporin suspended in ethanol, without the presence of water. Although Novartis accepts that Eon does not sell cyclosporin in the form of a hydrosol, it argued that when one of Eon's capsules is ingested, an infringing hydrosol is formed with the aqueous environment of the patient's stomach, and that Novartis's patent is infringed literally, as well as under the doctrine of equivalents (DOE) argument.

The two-judge majority looked at several dictionaries, first with regard to the meaning of 'hydrosol', and also 'solution' and 'medicinal'. The court agreed with the judgement of the Delaware district court that claim interpretation of 'hydrosol' did not include formation of the hydrosol in a patient's stomach after ingestion of a cyclosporin capsule. Both the specification, which repeatedly referred to the hydrosol as a 'pharmaceutical composition', and the prosecution history supported the court's interpretation. The DOE argument was also rejected because of the claimed requirement that the dispersion be prepared outside the body.

In dissent, Judge Clevenger argued that the majority had overworked the use of the dictionary to the point of error and that Federal Circuit case law has long recognized that medicines claimed in patents can be made inside or outside the body; infringement will occur in either case if the proper proofs are made.