Take mexiletine exactly as directed by your doctor, even though you may feel well. Do not take more medicine than ordered.

To lessen the possibility of stomach upset, mexiletine should be taken with food or immediately after meals or with milk or an antacid.

This medicine works best when there is a constant amount in the blood. To help keep this amount constant, do not miss any doses. Also it is best to take the doses at evenly spaced times day and night. For example, if you are to take 3 doses a day, the doses should be spaced about 8 hours apart. If this interferes with your sleep or other daily activities, or if you need help in planning the best times to take your medicine, check with your health care professional.

Dosing

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

The number of capsules that you take depends on the strength of the medicine.

• For oral dosage form (capsules):
  • For irregular heartbeat (arrhythmias):
    • Adults At first, 200 milligrams (mg) every eight hours. Then, your doctor may raise or lower your dose as needed.
    • Children Use and dose must be determined by your doctor.

Missed dose

If you miss a dose of this medicine and remember within 4 hours, take it as soon as possible. Then go back to your regular dosing schedule. 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• Do not keep outdated medicine or medicine no longer needed.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 mexiletine, the following should be considered:

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

Pregnancy Mexiletine has not been studied in pregnant women. However, studies in animals have shown that mexiletine causes a decrease in successful pregnancies but no birth defects. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.

Breast-feeding Mexiletine passes into breast milk. Because this medicine may cause serious side effects, breast-feeding is generally not recommended while you are receiving it. Be sure you have discussed this with your doctor before taking mexiletine.

Children Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of mexiletine in children with use in other age groups.

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 or if they cause different side effects or problems in older people. There is no specific information comparing use of mexiletine in the elderly with use in other age groups.

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.

Smoking

Smoking may decrease the effects of mexiletine.

• Congestive heart failure or
• Low blood pressure Mexiletine may make these conditions worse

• Heart attack (severe) or
• Liver disease Effects may last longer because of slower removal of mexiletine from the body

• Seizures (history of) Mexiletine can cause seizures