The length of time that Herceptin (trastuzumab) stays in your body varies from person to person depending on what dose of Herceptin you are having, how often you are having it and how your own body responds to it.

How long does Herceptin stay in your body?

The mean time it takes for Herceptin to be removed from a patient's body is 32 days.

This has been calculated using the mean half life of 5.8 days from a study where patients' first Herceptin dose was 4 mg/kg then they had a weekly dose of 2mg/kg.

• The half-life is the time it takes for your body to reduce the Herceptin plasma levels by half.
• It usually takes around 5.5 x elimination half-life for a drug to be eliminated from your system.
• Using Herceptin’s mean half-life 5.8 days
• 5.8 days X 5.5 = 31.9 days (32 days) for Herceptin to be cleared from your body

The range half-lives of Herceptin due to person to person variation was from 5.5 days to 176 days.

In the same study as above, the range in half-lives for Herceptin was between 1 to 32 days.

• For a half-life of 1 day, it would take only 5.5 days for most of the Herceptin to be removed from your body.
• For a half-life of 32 days, it would take 176 days for most of the Herceptin to be removed from your body.

The half-life of Herceptin is dependent on dose size, with a low 10mg dose taking 9.35 days, and a large 500mg dose takes 66 days.

When dose of Herceptin increases, the half life increases. This means when you have a larger dose it takes longer for your body to remove it.

• For a small 10mg dose of Herceptin given once weekly, the average half-life was 1.7 days. It would take 9.35 days for most of the Herceptin to be removed from your body.
• For a large 500mg dose of Herceptin given once weekly, the average half-life 12 days, it would take 66 days for most of the Herceptin to be removed from your body.