Grapefruit, orange and apple juice can wreak havoc with medications, a researcher said.

David Bailey of the University of Western Ontario reported nearly 20 years ago that grapefruit juice can cause drugs to absorb too quickly, potentially making them toxic. New work says that fruit juices can also slow how drugs are consumed by the body, possibly making them ineffective.

A news release on the work said that drugs for conditions such as heart disease and cancer -- as well as anti-rejection drugs after organ transplants -- can be affected.

Bailey's team had volunteers take an antihistamine used to fight allergies, either while drinking grapefruit juice, water flavored with the bitter component of grapefruit juice or plain water.

When taken with grapefruit juice, only half as much of the drug was absorbed as with water.

"This is just the tip of the iceberg," Bailey said. "I'm sure we'll find more and more drugs that are affected this way." Bailey advised patients to consult with a doctor or pharmacist before taking any medications with grapefruit juice or other fruits and juices.