In the U.S.—

• Vasodilator

Papaverine ( pa-PAV-er-een) belongs to the group of medicines called vasodilators. Vasodilators cause blood vessels to expand, thereby increasing blood flow. This medicine is used to treat problems resulting from poor blood circulation.

Papaverine is available only with your doctor's prescription, in the following dosage forms:

Oral
• Extended-release capsules (U.S.)
• Tablets (U.S. and Canada)

Parenteral
• Injection (U.S. and Canada)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For papaverine, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to papaverine. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Studies on effects in pregnancy have not been done in either humans or animals.

Breast-feeding—It is not known whether papaverine passes into the breast milk. However, this medicine has not been reported to cause problems in nursing babies.

Children—Although there is no specific information comparing use of papaverine in children with use in other age groups, this medicine is not expected to cause different side effects or problems in children than it does in adults.

Older adults—Papaverine may reduce tolerance to cold temperatures in elderly patients.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine, or if you smoke.

• Angina (chest pain) or
• Glaucoma or
• Heart disease or
• Myocardial infarction (``heart attack''), recent, or
• Stroke, recent—The chance of unwanted effects may be increased

If this medicine upsets your stomach, it may be taken with meals, milk, or antacids.

For patients taking the extended-release capsule form of this medicine:

• Swallow the capsules whole. Do not crush, break, or chew before swallowing. However, if the capsule is too large to swallow, you may mix the contents with jam or jelly and swallow without chewing.

Dosing—

The dose of papaverine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of papaverine. If your dose is different, do not change it unless your doctor tells you to do so:

• For oral dosage form (extended-release capsules):
  • Adults: 150 milligrams (mg) every twelve hours. The dose may be increased to 150 mg every eight hours or 300 mg every twelve hours.
• For oral dosage form (tablets):
  • Adults: 100 to 300 mg three to five times a day.
• For injection dosage form:
  • Adults: 30 to 120 mg every three hours injected slowly into the muscle or vein.
  • Children: 1.5 mg per kilogram (0.68 mg per pound) of body weight four times a day injected into the muscle or vein.

Missed dose—

If you miss a dose of this medicine, take it as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

It may take some time for this medicine to work. If you feel that the medicine is not working, do not stop taking it on your own. Instead, check with your doctor.

The helpful effects of this medicine may be decreased if you smoke. If you have any questions about this, check with your doctor.

Dizziness may occur, especially when you get up from a lying or sitting position or climb stairs. Getting up slowly may help. If this problem continues or gets worse, check with your doctor.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• Symptoms of overdose
  • Blurred or double vision;  drowsiness ;  weakness 
  
  

• Rare
  • Yellow eyes or skin 
  
  

Other side effects may occur after papaverine is given by injection. Check with your doctor if you notice any redness, swelling, or pain at the place of injection.

Other side effects that usually do not need medical attention may occur soon after an injection of this medicine. They usually go away after a little while. However, check with your doctor if any of the following side effects continue or are bothersome:

• Deep breathing;  dizziness;  fast heartbeat;  flushing of face 

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.