Methotrexate (Ectopic)

How it works

It inhibits dihydrofolate reductase, blocking folate-dependent DNA synthesis and thereby halting proliferation of the rapidly dividing trophoblastic tissue.

Prescribing in practice

• It is strictly contraindicated in viable intrauterine pregnancy and is highly teratogenic; appropriate patient selection (haemodynamic stability, low and falling expectations of trophoblast activity, no fetal cardiac activity) and exclusion of contraindications such as significant cytopenia, hepatic or renal impairment, and active infection are essential.
• Patients require clear safeguarding for rupture, with prompt surgical access available, as treatment can fail and tubal rupture may still occur.
• Avoid concurrent folate/folic acid supplements, non-steroidal anti-inflammatory drugs and alcohol around the time of treatment, and counsel against conception for a defined interval afterwards.

Monitoring

Track serum beta-hCG to confirm an adequate fall, with full blood count, renal and liver function checks and review for symptoms of rupture.

Counselling the patient

• Avoid alcohol, folic-acid-containing supplements and anti-inflammatory painkillers until advised otherwise.
• Use reliable contraception and delay pregnancy for the period your clinician specifies because the drug can harm a developing baby.
• Seek emergency care for worsening abdominal pain, dizziness or shoulder-tip pain, which may signal rupture.

Evidence & guidelines

UK guidance from NICE and the RCOG endorses single-dose intramuscular methotrexate for carefully selected ectopic pregnancies meeting strict eligibility criteria.