"Our research shows that the time of day that the medication is delivered is important in determining its effectiveness," said Peter H. Pan, M.D., an obstetrical anesthesiologist. "In the future, doctors may consider time of day, as well as patient's weight and other factors, when determining the best dose or method of drug delivery."
The study's goal was to determine if the body's natural internal rhythms can affect the effectiveness of pain medication for laboring women. The study, reported in the current issue of Anesthesiology, involved 77 women who were in labor with their first babies and requested spinal-epidural pain medication.
The research is part of the field of chronobiology that studies biologic rhythms. These rhythms include the circadian rhythm, the 24-hour body clock, and the ultradian rhythm, shorter-than-24-hour-cycles, which determine sleeping and eating patterns and can also affect blood pressure, heart rate and body temperature. Some rhythms are controlled by sunlight and others are controlled internally.
The researchers found that women who labored between noon and 6 p.m. got an average of 27 percent longer pain relief from a single dose of the spinal-epidural medication fentanyl than women whose labor was between 8 p.m. and 2 a.m. Fentanyl is one of the commonly used drugs for labor pain relief in the United States. However, this is one of the first studies to examine whether there are chronobiological variations in its effectiveness for labor pain relief.
"The right treatment given at the wrong time can be ineffective or create a crisis of escalating
Contact: Karen Richardson
Wake Forest University Baptist Medical Center