Phenobarbital is in a group of drugs called barbiturates (bar-BIT-chur-ates). Phenobarbital slows the activity of your brain and nervous system.

Belladonna alkaloids produce many effects in the body, including reduced muscle spasms in the digestive or urinary tract, and reduced fluid secretions from certain glands or organs.

The belladonna alkaloids included in this medication include atropine, hyoscyamine, and scopolamine.

The combination of belladonna alkaloids and phenobarbital is used to treat irritable bowel syndrome and ulcers in the intestine.

Belladonna alkaloids and phenobarbital may also be used for other purposes not listed in this medication guide.

Phenobarbital may be habit-forming and should be used only by the person it was prescribed for. This medication should never be shared with another person, especially someone who has a history of drug abuse or addiction. Keep the medication in a secure place where others cannot get to it.

Do not take this medication together with a potassium supplement unless your doctor has told you to.

Tell your doctor if you regularly use other medicines that make you sleepy (such as cold or allergy medicine, narcotic pain medicine, sleeping pills, muscle relaxers, and medicine for seizures, depression, or anxiety). They can add to sleepiness caused by belladonna alkaloids and phenobarbital.

This medication can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert.

Avoid drinking alcohol while taking this medication or you could have increased dizziness and drowsiness.

Avoid becoming overheated or dehydrated during exercise and in hot weather. Belladonna alkaloids and phenobarbital can decrease perspiration and you may be more prone to heat stroke.

Call your doctor if your symptoms do not improve, or if they get worse.

You should not use this medication if you are allergic to atropine, hyoscyamine, scopolamine, or phenobarbital. You may not be able use this medication if you have:

• enlarged prostate, urination problems;

• a blockage in your intestines or digestive tract;

• a stomach condition called paralytic ileus;

• active bleeding;

• severe ulcerative colitis or toxic megacolon;

• a muscle disorder called myasthenia gravis;

• a hiatal hernia or reflux disease; or

• porphyria.

Before taking this medication, tell your doctor if you are allergic to any drugs or if you have:

• a colostomy or ileostomy;

• liver disease;

• kidney disease;

• glaucoma;

• a thyroid disorder;

• heart disease, high blood pressure, congestive heart failure;

• a heart rhythm disorder; or

• ulcerative colitis or stomach ulcer.

If you have any of these conditions, you may not be able to take belladonna alkaloids and phenobarbital, or you may need a dose adjustment or special tests during treatment.

FDA pregnancy category C. This medication may be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

It is not known whether this medication passes into breast milk or if it could harm a nursing baby. However, belladonna alkaloids and phenobarbital can slow breast milk production. Do not take this medication without telling your doctor if you are breast-feeding a baby.

Do not give this medication to a child without the advice of a doctor.

Older adults may be more likely to have side effects such as constipation, dry mouth, problems with urination, agitation, confusion, or severe memory problems.