Q. When trying to sleep, my legs make me want to move them or get up to walk. What can I do?

A. You may have restless legs syndrome, which is a distressing desire to move your legs while just resting or sitting, especially at night. Bothersome RLS also occurs in 1 percent of 12- to 17-year-olds.

According to Johns Hopkins' Dr. Christopher Earley, there's often an uncomfortable feeling deep in the legs that may be described as a muscle ache or tension, or a feeling "like ants marching in my legs."

The more comfortable you are, the worse it is — you may even sleep better on a hard floor than in a soft bed. Common causes of RLS are iron deficiency, kidney dysfunction, diabetes, pregnancy and neuropathy, so get a fasting blood sugar and iron test. If you start iron pills due to ferritin levels below 50, check levels every three months to prevent iron overload and stop pills at a level of 50 or iron saturations above 50 percent.

Eighty percent of those with RLS also have periodic leg movements of sleep, or PLMS. However, PLMS also may be caused by other things besides RLS, such as sleep apnea and various antidepressant and anti-psychotic drugs.

If you need to sit a long time, keep your mind occupied reading exciting books, doing intricate needlework or playing video games. Avoid alcohol, caffeine and smoking. If symptoms remain bothersome and occur nightly, dopamine agonist drugs like Mirapex and Requip, used to treat Parkinson's disease, work best with the least side effects.

Start at a low dose two hours before symptoms usually start and increase dose gradually to avoid nausea and dizziness (which folks usually get used to in seven to 10 days). If one drug fails, try the other. If both fail, add or substitute the anticonvulsant gabapentin; opiates like codeine, hydrocodone, oxycodone or tramadol; or sedatives like clonazepam or Zolpidem. If there's pain, then gabapentin or opiates may be best. Go to www.rls.org for more information.

If you have problems only once or twice a week, consider the Parkinson's drug levodopa (Sinemet) when symptoms arise because it works within 20 minutes and causes less sedation than opiates. However, using it more than two nights a week can actually worsen restless legs. You may have to take an extra dose in the middle of the night, or combine rapid- and long-acting pills.

RLS can cause insomnia, causing daytime sleepiness, inattention, hyperactivity, decreased motivation and drive, as well as depression, so we need to take this under-diagnosed disease seriously and treat it aggressively.

Dr. Landis Lum is a family-practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i John A. Burns School of Medicine. Send questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.