The UK Teratology Information Service (UKTIS), August 2010, states the following regarding paternal exposure to methotrexate:
“There is very little published information on the potential teratogenicity following paternal exposure to methotrexate. There have been reports of alterations of the spermatozoa and oligospermia following exposure to methotrexate, however these effects appear to be reversible on cessation of treatment.
In practice, it is advisable to wait about six months (two sperm cycles) after such exposures before conception is planned. It is unusual for an increased risk of congenital malformations to be associated with exposure to drugs and/or chemicals in the father alone, unless they cause chromosomal abnormalities/point mutations.
A pregnancy following paternal exposure to methotrexate would not be regarded as an indication for termination of pregnancy or any invasive diagnostic procedures.”
The UKTIS advice does not differ for low-dose and high-dose paternal exposure to methotrexate.
This study provides some reassurance that this advice remains appropriate.
The manufacturer of Maxtrex™ tablets (methotrexate) states in the Summary of Product Characteristics that patients and their partners should be advised to avoid pregnancy until 3 months after cessation of methotrexate therapy.