Fingolimod may cause a slow heartbeat when you first start taking the drug.

It can cause a fast heartbeat and make it hard to focus.

Heart disease: Marijuana might cause rapid heartbeat and short-term high blood pressure.

Because high levels of potassium can cause an irregular heartbeat, it is always given slowly.

Heart conditions: Caffeine in green tea might cause irregular heartbeat.

Heart conditions: Caffeine can cause irregular heartbeat in sensitive people.

There is concern that creatine might cause irregular heartbeat in some people.

This can cause an abnormally fast, slow, or irregular heartbeat.

Stress, he said, may cause palpitations, rapid heartbeat and even heart failure.

So taking the two together may cause insomnia, jitters, and a rapid heartbeat.