What is isoniazid?
Isoniazid is an antibiotic. It prevents tuberculous bacteria from multiplying in the body.
Isoniazid is used to treat and to prevent tuberculosis (TB).
Isoniazid may also be used for purposes other than those listed in this medication guide.
What should I discuss with my healthcare provider before taking isoniazid?
Before taking this medication, tell your doctor if you have
You may not be able to take isoniazid, or you may require a dosage
adjustment or special monitoring during treatment if you have any of the conditions listed above.
It is not known whether isoniazid 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.
It is not known whether isoniazid will be harmful to a nursing baby. Do not take this
medication without first talking to your doctor if you are breast-feeding a baby.
How should I take isoniazid?
Take isoniazid exactly as directed by your doctor. If you do not understand these instructions,
ask your pharmacist, nurse, or doctor to explain them to you.
Take each dose with a full glass (8 ounces) of water.
Take isoniazid on an empty stomach 1 hour before or 2 hours after meals.
If nausea occurs, ask your doctor if you can take isoniazid with food.
Take all of the isoniazid that has been prescribed for you even if you begin to feel better.
Your symptoms may begin to improve before the infection is completely treated.
It is important to take isoniazid regularly to get the most benefit.
Your doctor may also want you to take a supplemental vitamin B6 (pyridoxine) tablet daily
during treatment to prevent numbness and tingling caused by low levels of this vitamin.
Your doctor may want you to have blood tests or other medical evaluations during treatment
with isoniazid to monitor progress and side effects.
Store this medication at room temperature away from moisture and heat.
What happens if I miss a dose of isoniazid?
Take the missed dose as soon as you remember. If it is almost time for the next regularly
scheduled dose, skip the missed dose and take the next one as directed.
Do not
take
a double dose of this medication.
Where can I get more information about isoniazid?
Your pharmacist has information about isoniazid written for health professionals that you may read.
What are the possible side effects of isoniazid?
If you experience any of the following serious side effects, stop taking isoniazid 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);
-
unusual weakness or fatigue;
-
nausea, vomiting, or loss of appetite;
-
abdominal pain;
-
yellow skin or eyes;
-
dark urine;
-
numbness or tingling in your hands or feet;
-
seizures;
-
blurred vision; or
-
confusion or abnormal behavior.
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.
What is the most important information I should know about isoniazid?
Take all of the isoniazid that has been prescribed for you even if you begin to feel better.
Your symptoms may begin to improve before the infection is completely treated.
Avoid alcohol while taking isoniazid. Alcohol may increase the risk of damage to the liver
during isoniazid treatment.
Contact your doctor immediately if you experience numbness or tingling in the hands or feet,
weakness, fatigue, loss of appetite, nausea and vomiting, yellowing of the skin or eyes, or darkening of
the urine.
What should I avoid while taking isoniazid?
Avoid alcohol while taking isoniazid. Alcohol will increase the risk of damage to the liver
during treatment with this medication.
Use caution with the foods listed below. They can interact with isoniazid and cause a reaction
that includes a severe headache, large pupils, neck stiffness, nausea, vomiting, diarrhea, flushing,
sweating, itching, irregular heartbeats, and chest pain. A reaction will not necessarily occur, but eat
these foods with caution until you know if you will react to them. Call your doctor immediately if you
experience any of these symptoms.
Eat the following foods with caution:
-
cheeses, including American, Blue, Boursault, Brick, Brie,
Camembert, Cheddar, Emmenthaler, Gruyere, Mozzarella, Parmesan, Romano, Roquefort,
Stilton, and Swiss;
-
sour cream and yogurt;
-
beef or chicken liver, fish, meats prepared with tenderizer,
bologna, pepperoni, salami, summer sausage, game meat, meat extracts, caviar, dried fish,
herring, shrimp paste, and tuna;
-
avocados, bananas, figs, raisins, and sauerkraut;
-
soy sauce, miso soup, bean curd, and fava beans;
-
yeast extracts;
-
ginseng;
-
chocolate;
-
caffeine (coffee, tea, cola, etc.); and
-
beer (alcoholic and nonalcoholic), red wine (especially
Chianti), sherry, vermouth, and other distilled spirits.
What other drugs will affect isoniazid?
Before taking isoniazid, tell your doctor if you are taking any of the following drugs:
-
antacids. Aluminum salts will decrease the action of isoniazid. Do
not take antacids that contain aluminum for 1 to 2 full hours before or after taking a dose of
isoniazid.
-
ketoconazole (Nizoral) and itraconazole (Sporanox).
Isoniazid may decrease the actions of these antifungal medicines. Therefore, a fungal infection
may not be adequately treated.
-
rifampin (Rimactane, Rifadin) or rifabutin (Mycobutin).
-
disulfiram (Antabuse). Unusual behavior and coordination
difficulties may occur if these medicines are taken together.
Isoniazid may increase the effects of the following medicines:
-
warfarin (Coumadin);
-
carbamazepine (Tegretol);
-
cycloserine (Seromycin);
-
phenytoin (Dilantin), ethotoin (Peganone), and
mephenytoin (Mesantoin);
-
meperidine (Demerol);
-
benzodiazepines such as alprazolam (Xanax), diazepam
(Valium), lorazepam (Ativan), and temazepam (Restoril);
-
theophylline (Theo-Dur, Theochron, Theolair, Elixophyllin,
Slo-Phyllin, others);
-
ethionamide (Trecator-SC).
You may require a dosage adjustment or special monitoring if you are taking
any of the medicines listed above.
Drugs other than those listed here may also interact with isoniazid. Talk to your doctor and
pharmacist before taking any prescription or over-the-counter medicines, including vitamins, minerals,
and herbal products.
What happens if I have an overdose of isoniazid?
