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                                                                    EXHIBIT 23.1
 
                        CONSENT OF INDEPENDENT AUDITORS
 
     We consent to the reference to our firm under the captions "Experts" and
"Selected Financial Data" and to the use of our reports dated October 11, 1997,
in the Registration Statement (Form S-1 No. 333-          ) and related
Prospectus of Penwest Pharmaceuticals Co. for the registration of 2,875,000
shares of its common stock.
 
                                          ERNST & YOUNG LLP
 
Stamford, Connecticut
October 20, 1997