From the FAA's guidance notes Q&A:
Question 2: Is it permissible to be issued our U.S. pilot certificate on the basis of the person’s foreign pilot license by permitting the applicant to use a current FAA medical certificate if the applicant’s foreign medical license has expired?
Answer 2: Ref. § 61.75(b)(4); If the verification from the foreign civil aviation authority states that the foreign pilot license is valid, but the foreign medical license has expired then in accordance with § 61.75(b)(4), it is permissible to accept the FAA medical certificate as meeting the requirement for a current medical certificate. If the foreign civil aviation authority specifically states [emphasis added: it must state it on the foreign pilot license] that the foreign pilot license is not valid because the medical endorsement/license has expired, then a U.S. pilot certificate may not be issued to the applicant.