- Women of childbearing potential must use a medically acceptable contraceptive regimen from study treatment initiation until at least 30 days after the last dose of pralatrexate and must have a negative serum pregnancy test within 14 days prior to the first day of study treatment. Serum pregnancy test not required for patients who are postmenopausal (greater than 12 months since last menses) or are surgically sterilized.