Pfizer’s Viagra patent is held to be invalid in Canada

Whilst patent applications are submitted to an examination process some patents are granted that are later held to be invalid.  This has been reported to have occurred in the case of the Pfizer patent in Canada for the penile erectile malfunction drug called Viagra.

Third parties should always seek advice from a patent attorney in respect of a patent which is of concern to their business activities in case its validity can be challenged.  For example, in Europe, the opposition procedure before the European Patent Office can be used to challenge the validity of a European patent within nine months of grant.