Side effects of CDK4/6 inhibitors

Each different CDK4/6 inhibitor has different side effects but most of them are not severe. 

It is very unlikely you will experience all or even many of them. Usually, they are easy to manage them and they settle over time.

Talk to your doctor or breast care nurse about ways to manage side effects.

Side effects from CDK4/6 inhibitors can often be managed by:

• reducing the dose
• changing to another CDK4/6 inhibitor.

The most common side effects are:

• neutropenia (not enough 'neutrophils' - a type of white blood cells)
• low platelets
• reduced appetite
• tiredness
• nausea
• diarrhoea
• mouth ulcers
• hair thinning
• sore throat, runny nose and sneezes
• sore back
• headache
• swollen hands, ankles or feet
• dizziness or light headedness
• inflammation of the lungs.

Abemaciclib is more likely to cause diarrhoea and gastrointestinal upset, but less likely to cause neutropenia.

Ribociclib can, rarely, cause a change in the rhythm of the heart (QT prolongation). Your doctor will send you for ECG monitoring before treatment. You should avoid ribociclib if you already have a prolonged QT interval, or are on drugs that can cause it.

Low white blood counts are common with palbociclib and ribociclib but rarely lead to hospitalisation.