Pain expert Dr. Scott Fishman answers questions about pain medication:

Q: What are the chances of overdosing with patient-controlled analgesia?

A: Patient-controlled analgesia (PCA) has built-in safety features that protect a patient from giving himself too large a dose or too many doses. Despite many people's fears about abuse of PCA, there is evidence that patients in charge of their own medication are better off than those who need injections from caregivers.

Giving pain-relieving drugs on demand is a relatively new concept. The first device was developed by doctors at Stanford University Medical Center in 1970 and was called the Demand Dropmaster. It delivered a dose of analgesia when a patient pressed a button on a handgrip. With a few modifications, the Demand Dropmaster soon after evolved into the PCA device.

The PCA safely delivers pain medicine through a pump loaded with a drug like morphine. It is equipped with a button that the patient can push whenever he feels pain. However, the PCA does have limits. The doctor sets the upper limit of medicine patients can give themselves with each push, which is called the demand dose. The doctor also adjusts the pump for how many doses can be given in a certain period (called the "lockout").

Usually, doses are limited to one every five or ten minutes, no matter how many times the button is pushed. The device has an added fail-safe, which is the action of the narcotic itself. As long as the patient is the only one who uses the button, it is highly unlikely that a patient will overdose himself.

Because each individual dose is too small to cause an overdose, the drug will make the patient drowsy and eventually put him to sleep if too much is taken. The patient's drowsiness and subsequent sleep obviously stops any further pushes on the button and, of course, any more medication. This fail-safe is only effective if the patient is the one in control of the button.

PCA is not only safe, but smart as well. Its effectiveness depends on the one person who knows best how much medication is needed and when: the patient.