Take this medicine exactly as directed. Do not take more of this medicine and do not take it more often than your doctor ordered. Do not miss any doses.

Taking quinidine with food may help lessen stomach upset.

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

• Quinidex Extentabs or Biquin Durules Swallow the tablets whole; do not break, crush, or chew before swallowing. Note that Biquin Durules may sometimes appear as a whole tablet in the stool; this tablet is just the empty shell that is left after the medicine has been absorbed into the body.
• Quinaglute Duratabs or Quin-Release These tablets may be broken in half; however, they should not be crushed or chewed before swallowing.

Dosing

The dose of quinidine 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 quinidine. If your dose is different, do not change it unless your doctor tells you to do so.

The number of tablets that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are taking quinidine.

• For regular (short-acting) oral dosage form (tablets):
  • For abnormal heart rhythm:
    • Adults 200 to 650 milligrams (mg) three or four times a day.
    • Children 30 to 40 mg per kilogram (kg) (13.6 to 18.2 mg per pound) of body weight per day. Your doctor may increase the dose if needed.
• For long-acting oral dosage form (tablets):
  • For abnormal heart rhythm:
    • Adults 300 to 660 mg every eight to twelve hours.
    • Children 30 to 40 mg per kilogram (kg) (13.6 to 18.2 mg per pound) of body weight per day. Your doctor may increase the dose if needed.
• For injection dosage form:
  • For abnormal heart rhythm:
    • Adults 190 to 380 mg injected into the muscle every two to four hours. Or, up to 0.25 mg per kg (0.11 mg per pound) of body weight per minute in a solution injected into a vein.
    • Children Dose must be determined by your doctor.
  • For malaria:
    • Adults 10 mg per kg (4.54 mg per pound) of body weight in a solution injected slowly into a vein over one to two hours. Then, 0.02 mg per kg (0.009 mg per pound) of body weight per minute is given. Or, 24 mg per kg (10.91 mg per pound) of body weight in a solution injected slowly into a vein over a four-hour period. Then, eight hours after the first dose, 12 mg per kg (5.45 mg per pound) of body weight, injected slowly into a vein over a four-hour period, and repeated every eight hours.
    • Children Dose must be determined by your doctor.

Missed dose

If you miss a dose of this medicine and remember within 2 hours of the missed dose, take it as soon as possible. However, if you do not remember until later, 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.

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 quinidine, the following should be considered:

Allergies Tell your doctor if you have ever had any unusual or allergic reaction to quinidine or quinine. 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. However, quinidine has been used during pregnancy and, although serious side effects are uncommon, it has been shown to cause mild uterine contractions, premature labor, and blood problems in the neonate.

Breast-feeding Quinidine passes into breast milk and, because of the potential for problems in the nursing infant, it is generally not recommended in mothers who are breast-feeding.

Children Quinidine has not been widely studied in children; however, it is used in children to treat abnormal heart rhythms and to treat malaria. Children may be able to take higher doses than adults and may have fewer side effects (such as vomiting, loss of appetite, and diarrhea) than adults.

Older adults Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing use of quinidine in the elderly with use in other age groups, this medicine is not expected to cause different side effects or problems in older people than it does in younger adults. However, quinidine may remain in the bodies of older adults longer than it does in younger adults, which may increase the risk of side effects and which may require lower doses.

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. When you are taking quinidine, it is especially important that your health care professional know if you are taking any of the following:

• Amiodarone Effects may be increased because levels of quinidine in the body may be increased

• Digitalis medicines (heart medicine) Effects may be increased because levels of digitalis in the body may be increased

• Antidepressants, tricyclic, such as amitriptyline (e.g., Elavil), clomipramine (e.g., Anafranil), desipramine (e.g., Norpramin), doxepin (e.g., Sinequan), imipramine (e.g., Tofranil), and nortriptyline (e.g., Pamelor) or
• Astemizole (e.g., Hismanal) or
• Chloroquine (e.g., Aralen) or
• Clarithromycin (e.g., Biaxin) or
• Cisapride (e.g., Propulsid) or
• Diphenhydramine (e.g., Benadryl) or
• Erythromycin (e.g., Erythrocin, Erytab) or
• Fludrocortisone (e.g., Florinef) or
• Halofantrine (e.g., Halfan) or
• Haloperidol (e.g., Haldol) or
• Indapamide (e.g., Lozol) or
• Maprotiline (e.g., Ludiomil) or
• Mefloquine (e.g., Lariam) or
• Other heart medicine, including bepridil (e.g., Vascor), beta-adrenergic blocking agents such as propranolol (e.g., Inderal), diltiazem (e.g., Cardizem), disopyramide (e.g. Norpace), encainide (e.g., Encaid), flecainide (e.g., Tambocor), ibutilide (e.g., Corvert), lidocaine (e.g., Xylocaine), procainamide (e.g., Procanbid), propafenone (e.g., Rythmol), sotalol (e.g., Betapace, Sotacor), tocainide (e.g., Tonocard), and verapamil (e.g., Calan, Isoptin) or
• Pentamidine (e.g., NebuPent, Pentam) or
• Phenothiazines (e.g., chlorpromazine [e.g., Thorazine], perphenazine [e.g., Trilafon], prochlorperazine [e.g., Compazine], thioridazine [e.g., Mellaril]) or
• Pimozide (e.g., Orap) or
• Risperidone (e.g., Risperdal) or
• Sparfloxacin (e.g., Zagam) or
• Tamoxifen (e.g., Nolvadex) or
• Thiothixene (e.g., Navane) or
• Trimethoprim and sulfamethoxazole combination (e.g., Bactrim, Septra) Effects on the heart may be increased

• Urinary alkalizers (medicine that makes the urine less acid, such as acetazolamide [e.g., Diamox], dichlorphenamide [e.g., Daranide], methazolamide [e.g., Neptazane], and sodium bicarbonate [baking soda]) Effects may be increased because levels of quinidine in the body may be increased

• Electrolyte disorders Quinidine may worsen heart rhythm problems

• Heart disease or
• Myasthenia gravis Quinidine may make these conditions worse

• Kidney disease or
• Liver disease Effects may be increased because of slower removal of quinidine from the body