How long does methotrexate stay in your system?

The estimated length of time it takes for methotrexate to be removed from your body is:

• For low dose methotrexate ranges from 16.5 hours to 55 hours.
• For high dose methotrexate ranges from 44 hours to 82.5 hours.

The length of time it takes for a medicine to be removed from your body depends on the drug's elimination half-life. It takes 5.5 x elimination half-life for most of a medicine to be removed from your system.

For low dose methotrexate the half life range is 3 to 10 hours so

• 3 hours X 5.5 = 16.5 hours.
• 10 hours X 5.5 hours = 55 hours.
• Therefore for the estimated elimination time range for low dose methotrexate is 16.5 hours to 55 hours.

For high dose methotrexate the half life range is 8 to 15 hours so

• 8 hours X 5.5 hours = 44 hours.
• 15 hours X 5.5 hours = 82.5 hours.
• Therefore the estimated elimination time range for high dose methotrexate is 44 hours to 82.5 hours.

Elimination times are an estimate and can vary due to patient-specific variables and drug-specific variables including:

• How much and how often you have taken the drug.
• Your metabolic rate – a slower metabolism will increase the time a drug remains in your system and a faster metabolism will decrease the time a drug remains in your system.
• Your age and health issues – older age and poor health may change the time the drug says in your system.
• Body mass.
• Drug formulation, way of administration, pharmacokinetics, volume of distribution etc.