Interaction

Tyrosine kinase inhibitors, like many other drugs, are metabolised and broken down by certain enzymes in the liver. Thus, many drugs can influence the effect of tyrosine kinase inhibitors, but tyrosine kinase inhibitors can also influence other drugs. The effect can be enhanced, which is associated with an increased risk of side effects; or reduced, which leads to a weakening of the effectiveness of cancer therapy.

Patients should inform the treating physician about any medication they are taking, even if it is a herbal drug. St. John’s wort, for example, which is used to treat mild to moderate depression, can accelerate the breakdown of tyrosine kinase inhibitors and weaken the effect. Other medications that can interact with tyrosine kinase inhibitors are immune system suppressors, psychotropic drugs, epilepsy medications, high blood pressure medications and cholesterol-lowering drugs.

Other commonly used drugs such as paracetamol or blood thinners also interact when used concurrently. Patients should discuss the use of other drugs with their doctor and pharmacist. During treatment with tyrosine kinase inhibitors, the consumption of alcohol is not necessarily prohibited. Alcohol should be consumed in moderation, and care must be taken to continue taking the medication regularly. If vomiting or diarrhea occurs, the effectiveness of the tyrosine kinase inhibitor may be reduced.

Contraindications – When should a tyrosine kinase inhibitor not be taken?

Tyrosine kinase inhibitors must not be taken if there is an allergy to the active ingredient or other components of the drug. Before taking it, the treating physician should be informed about existing or past liver, kidney or heart diseases. Past hepatitis B infections should also be examined, as the disease can be reactivated and can be fatal. Patients taking the thyroid hormone preparation Levothyroxine should also inform their doctor about it. Tyrosine kinase inhibitors may decrease the effectiveness of these drugs, so thyroid function should be checked regularly and the dose adjusted.

Dosage

There are a large number of tyrosine kinase inhibitors that have to be dosed differently depending on the indication and patient.Patients should pay close attention to their doctor’s or pharmacist’s instructions, as correct intake is a prerequisite for the effectiveness of the drug. The usual dose in the treatment of chronic myeloid leukemia with the drug Gleevec (which contains the active ingredient imatinib, a tyrosine kinase inhibitor) is 400 or 600 mg once daily (for capsules of 100 mg each, this makes 4 or 6 capsules).