If deductible, they would be a deduction in the year paid.

IRC 1.213-1(a)(3)(i)

For medical expenses paid (including expenses paid for medicine and drugs) to be deductible, they must be for medical care of the taxpayer, his spouse, or a dependent of the taxpayer and not be compensated for by insurance or otherwise. Expenses paid for the medical care of a dependent, as defined in section 152 and the regulations thereunder, are deductible under this section even though the dependent has gross income equal to or in excess of the amount determined pursuant to § 1.151-2 applicable to the calendar year in which the taxable year of the taxpayer begins. Where such expenses are paid by two or more persons and the conditions of section 152(c) and the regulations thereunder are met, the medical expenses are deductible only by the person designated in the multiple support agreement filed by such persons and such deduction is limited to the amount of medical expenses paid by such person.