A recent decision of the Federal Court expounded on the harm that can occur if two patents issue for the same invention. The Honourable Mr. Justice O'Reilly effectively quashed any suggestion in prior case law that patentees could use public dedications to overcome the effects of double patenting, which would otherwise allow them to extend their monopoly.

In Merck & Co. Inc. v. Canada (Health), Merck brought an application under the Patented Medicines (Notice of Compliance) Regulations (SOR/93-133) (the NOC Regulations) seeking an order prohibiting the Minister of Health (the Minister) from issuing a notice of compliance (NOC) to Apotex Inc. (Apotex) for the medicine dorzolamide, used in the treatment of glaucoma, until after the expiry of Canadian Patent No. 1,329,211 (the ‘211 Patent).

Apotex argued that the ‘211 Patent was invalid for double-patenting. In particular, before it obtained the ‘211 Patent, Merck had already received a patent (known as the ‘262 Patent) for a family of compounds that included dorzolamide. Apotex therefore contended that Merck was not entitled to a second patent for the same invention. Merck, on the other hand, maintained that Apotex’s allegation of invalidity was unjustified because Merck had voluntarily relinquished its rights under the earlier ‘262 Patent by dedicating it to the public in 2007. In particular, Merck alleged that once it dedicated the ‘262 Patent, it no longer had two patents for the same invention, so the later patent could not be invalid on grounds of double-patenting . The Court determined that Merck had not met its burden of proof to demonstrate that Apotex’s allegation of invalidity was unjustified, and accordingly dismissed Merck’s application.


Merck applied for the ‘262 Patent before the 1989 amendments to the Patent Act came into force, and the application was thus governed by the “old Act” (R.S.C. 1985, c. P-4). The ‘211 Patent was a “divisional” of the ‘262 Patent, so it was deemed to have the same application date. Both patents were therefore subject to the old Act and set to expire 17 years after issuance, with the ‘211 Patent expiring 28 days after the ‘262 Patent.

Apotex served a first NOA in respect of the ‘211 Patent on May 19, 2007. Merck responded by applying to the Court to prohibit the Minister from issuing a NOC to Apotex. Then Merck, on October 3, 2007, served its notice of dedication in respect of the ‘262 Patent. In turn, Apotex withdrew its original NOA and served a new one specifically alleging that both the ‘211 Patent and the ‘262 Patent claimed a monopoly for dorzolamide. As both parties agreed that the ‘262 and ‘211 Patents included claims to dorzolamide, the case turned solely on the effect of Merck’s dedication of the ‘262 Patent to the public.

Effect of the Dedication

The Patent Act contains two mechanisms for correcting faulty patents: reissue (s. 47) and disclaimer (s. 48). These procedures allow patentees to correct inadvertent errors:

47. Whenever any patent is deemed defective or inoperative by reason of insufficient description and specification, or by reason of the patentee’s claiming more or less than he had a right to claim as new, but at the same time it appears that the error arose from inadvertence, accident or mistake, without any fraudulent or deceptive intention, the Commissioner may … cause a new patent, in accordance with an amended description and specification … to be issued to [the patentee] for the same invention for the then unexpired term for which the original patent was granted.

48. Whenever, by any mistake, accident or inadvertence, and without any wilful intent to defraud or mislead the public, a patent has (a) made a specification too broad … or (b) in the specification, claimed that the patentee … was the inventor of any material or substantial part of the invention patented of which the patentee was not the inventor, and to which the patentee had no lawful right, the patentee may … make a disclaimer of such parts as the patentee does not claim to hold by virtue of the patent …

Dedications, on the other hand, are a creature of common law, and allow a patentee to publicly declare that it will not enforce its monopoly.

Earlier decisions had determined that public dedications had the effect of a removing the evidentiary basis for allegations of double patenting. The Court of Appeal distinguished these cases on the basis that in those cases the dedication would not have conferred an advantage on the patentee. In the case at hand, however, the Court found that if it were to accept this argument, Merck would have achieved an extended monopoly over its invention for a period of 17 years and 28 days, more than the 17-year statutory period.

The Court found that if Merck had made a good faith mistake when it acquired the ‘211 Patent as a divisional, it had available to it the remedies of reissuance or disclaimer under the Patent Act to rectify any error. The legal effect of these remedies would have been to sever off the overlapping claims of the ‘211 Patent. In a case such as the present, where a patentee obtained a divisional patent that did not conform to the Patent Act, the remedy was provided by the prohibition against double-patenting. The Court noted:

"From a global perspective, when considering the harm that may result from an improper divisional, it becomes clear that the principle of double patenting provides a sufficient remedy. The harm is that two patents might issue for the same invention, giving the patentee differing monopolies.

In the result, Apotex’s allegation of invalidity for double-patenting was justified, and Merck’s application for prohibition was dismissed.