Contact your doctor immediately if you experience ringing in the ears, changes in vision, dizziness, fainting, a rapid heartbeat, headache, nausea, a rash, or difficulty breathing.
Do not skip doses or change your dosing schedule without talking to your doctor. Changing your schedule could make your condition worse.
Quinidine may be taken with food to lessen stomach upset.
Do not crush, chew, or break any extended- or sustained-release formulations of quinidine. Swallow them whole. If you are not sure whether you have a long-acting form of quinidine, ask your pharmacist, nurse, or doctor.
Before taking quinidine, tell your doctor if you have
had an allergic reaction or the development of blood problems (e.g., thrombocytopenic purpura) due to previous treatment with quinidine or quinine;
any other type of heart disease or heart problems;
liver disease;
kidney disease; or
myasthenia gravis (a nerve-muscle disorder).
You may not be able to take quinidine, or you may require a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.
Quinidine is in the FDA pregnancy category C. This means that it is not known whether quinidine will be harmful to an unborn baby. Do not take this medication without first talking to your doctor if you are pregnant or could become pregnant during treatment.
Quinidine passes into breast milk. It is not known whether quinidine will affect a nursing infant. Do not take this medication without first talking to your doctor if you are breast-feeding a baby.
Take quinidine exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.
Take each dose with a full glass of water.
Quinidine may be taken with food to lessen stomach upset.
Do not crush, chew, or break any extended- or sustained-release formulations of quinidine. Swallow them whole. If you are not sure whether you have a long-acting form of quinidine, ask your pharmacist, nurse, or doctor.
Do not skip doses or change your dosing schedule without talking to your doctor. Changing your schedule could make your condition worse.
It is important to take quinidine regularly to get the most benefit.
Your doctor may want you to have blood tests or other medical evaluations during treatment with quinidine to monitor progress and side effects.
Grapefruit and grapefruit juice may interact with quinidine. The interaction could lead to potentially adverse effects. You should discuss the use of grapefruit and grapefruit juice with your doctor. Do not increase or decrease the amount of grapefruit products in your diet without first talking to your doctor.
Store quinidine at room temperature away from moisture and heat.
Take the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and take only the next regularly scheduled dose. Do not take a double dose of this medication. A double dose could be dangerous.
Grapefruit and grapefruit juice may interact with quinidine. The interaction could lead to potentially adverse effects. You should discuss the use of grapefruit and grapefruit juice with your doctor. Do not increase or decrease the amount of grapefruit products in your diet without first talking to your doctor.
If you experience any of the following serious side effects, stop taking quinidine and seek emergency medical attention or contact your doctor immediately:
an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
a new or a worsening irregular heartbeat pattern;
chest pain or chest discomfort;
ringing in the ears;
changes in vision;
dizziness, fainting, or headache;
rash;
difficulty breathing;
abdominal pain, nausea, or vomiting; or
yellowing of the skin or eyes.
Other, less serious side effects may be more likely to occur. Continue to take quinidine and talk to your doctor if you experience
mild upset stomach;
headache;
decreased appetite;
diarrhea; or
muscle weakness.
Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome. You may report side effects to FDA at 1-800-FDA-1088.
another medicine to treat irregular heartbeats such as bepridil (Vascor), dofetilide (Tikosyn), procainamide (Procan SR, Procanbid, Pronestyl), disopyramide (Norpace), and others;
a beta-blocker such as atenolol (Tenormin), metoprolol (Lopressor), propranolol (Inderal), and others;
a tricyclic antidepressant such as amitriptyline (Elavil), doxepin (Sinequan), clomipramine (Anafranil), imipramine (Tofranil), others; or
a phenothiazine such as chlorpromazine (Thorazine), promethazine (Phenergan, Promethegan), prochlorperazine (Compazine), and others.
You may not be able to take quinidine, or you may require a dosage adjustment or special monitoring if you are taking any of the medicines listed above.
Many drugs other than those listed here can interact with quinidine, resulting in dangerous side effects and/or decreased effectiveness. Do not take any other prescription or over-the-counter medications, including herbal products, during treatment with quinidine without first talking to your doctor or pharmacist.
Your pharmacist has more information about quinidine written for health professionals that you may read.
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