Drug Information

Isoniazid is an antibiotic used to prevent and treat tuberculosis. To prevent development of resistant tuberculosis bacteria, people with tuberculosis are treated with long courses of combination drug therapy, most commonly isoniazid, rifampin, and pyrazinamide.

Common brand names:

Nydrazid

Summary of Interactions with Vitamins, Herbs, & Foods

Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

  • Potassium

    Tetracycline can interfere with the activity of folic acid, potassium, and vitamin B2, vitamin B6, vitamin B12, vitamin C, and vitamin K. This is generally not a problem when taking tetracycline for two weeks or less. People taking tetracycline for longer than two weeks should ask their doctor about vitamin and mineral supplementation. Taking 500 mg vitamin C simultaneously with tetracycline was shown to increase blood levels of tetracycline in one study. The importance of this interaction is unknown.

    Taking large amounts of niacinamide, a form of vitamin B3, can suppress inflammation in the body. According to numerous preliminary reports, niacinamide, given in combination with tetracycline or minocycline, may be effective against bullous pemphigoid, a benign, autoimmune blistering disease of the skin. Preliminary evidence also suggests a similar beneficial interaction may exist between tetracycline and niacinamide in the treatment of dermatitis herpetiformis.

  • Vitamin B12

    Isoniazid may interfere with the activity of other nutrients, including vitamin B3 (niacin), vitamin B12, vitamin D, and vitamin E, folic acid, calcium, and magnesium. Supplementation with vitamin B6 is thought to help prevent isoniazid-induced niacin deficiency; however, small amounts of vitamin B6 (e.g. 10 mg per day) appear to be inadequate in some cases. People should consider using a daily multivitamin-mineral supplement during isoniazid therapy.

  • Vitamin B2

    Tetracycline can interfere with the activity of folic acid, potassium, and vitamin B2, vitamin B6, vitamin B12, vitamin C, and vitamin K. This is generally not a problem when taking tetracycline for two weeks or less. People taking tetracycline for longer than two weeks should ask their doctor about vitamin and mineral supplementation. Taking 500 mg vitamin C simultaneously with tetracycline was shown to increase blood levels of tetracycline in one study. The importance of this interaction is unknown.

  • Vitamin B3 (Niacin)

    Isoniazid is capable of causing vitamin B3 (niacin) deficiency, most likely due to its ability to interfere with cell-repair enzymes made from niacin. Significant niacin deficiency, also known as pellagra, features dermatitis, diarrhea, and dementia (impaired intellectual function). Supplementation with vitamin B6 is thought to reduce this risk, although small amounts (e.g. 10 mg daily) has been noted to be inadequate in some cases.

  • Vitamin B6
    Supplementation with vitamin B6 is thought to help prevent isoniazid-induced niacin deficiency; however, small amounts of vitamin B6 (e.g. 10 mg per day) appear to be inadequate in some cases.

    Isoniazid can interfere with the activity of vitamin B6. Vitamin B6 supplementation is recommended, especially in people with poor nutritional status, to prevent development of isoniazid-induced peripheral neuritis (inflamed nerves). One case is reported in which injectable vitamin B6 reversed isoniazid-induced coma. In another case, however, 10 mg per day of vitamin B6 failed to reverse isoniazid-induced psychosis. The author suggested that higher amounts (e.g., 50 mg per day) may be needed. Although the optimal amount remains unknown, some doctors suggest that adults taking isoniazid supplement with 100 mg of vitamin B6 per day to prevent side effects. However, as animal studies suggest that very large amounts of vitamin B6 can interfere with the effect of isoniazid,people taking isoniazid should consult their doctor to determine the appropriate amount of vitamin B6 to take.

  • Vitamin K

    Many antibiotics taken by mouth, including isoniazid, may kill friendly bacteria in the large intestine that produce vitamin K. Vitamin K1 (phylloquinone) is now found in some multivitamins.

  • Calcium

    Isoniazid may interfere with the activity of other nutrients, including vitamin B3 (niacin), vitamin B12, vitamin D, and vitamin E, folic acid, calcium, and magnesium. Supplementation with vitamin B6 is thought to help prevent isoniazid-induced niacin deficiency; however, small amounts of vitamin B6 (e.g. 10 mg per day) appear to be inadequate in some cases. People should consider using a daily multivitamin-mineral supplement during isoniazid therapy.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Folic Acid

    Isoniazid may interfere with the activity of other nutrients, including vitamin B3 (niacin), vitamin B12, vitamin D, and vitamin E, folic acid, calcium, and magnesium. Supplementation with vitamin B6 is thought to help prevent isoniazid-induced niacin deficiency; however, small amounts of vitamin B6 (e.g. 10 mg per day) appear to be inadequate in some cases. People should consider using a daily multivitamin-mineral supplement during isoniazid therapy.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Magnesium

    Isoniazid may interfere with the activity of other nutrients, including vitamin B3 (niacin), vitamin B12, vitamin D, and vitamin E, folic acid, calcium, and magnesium.People should consider using a daily multivitamin-mineral supplement during isoniazid therapy.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Vitamin D

    Isoniazid may interfere with the activity of other nutrients, including vitamin B3 (niacin), vitamin B12, vitamin D, and vitamin E, folic acid, calcium, and magnesium. People should consider using a daily multivitamin-mineral supplement during isoniazid therapy.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Vitamin E

    Isoniazid may interfere with the activity of other nutrients, including vitamin B3 (niacin), vitamin B12, vitamin D, and vitamin E, folic acid, calcium, and magnesium. People should consider using a daily multivitamin-mineral supplement during isoniazid therapy.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Reduce Side Effects

  • L-Carnitine
    Some drugs used to treat tuberculosis (including isoniazid, rifampin, and pyrazinamide) may cause liver damage. In a double-blind study of patients starting treatment for tuberculosis with the combination of isoniazid, rifampin, ethambutol, and pyrazinamide, supplementation with L-carnitine (1,000 mg twice a day for 4 weeks) significantly decreased the number of patients who developed drug-induced liver damage (17% with L-carnitine, 32% with placebo).
  • Milk Thistle
    In a double-blind trial, supplementation with silymarin (a substance present in milk thistle) in the amount of 140 mg 3 times per day prevented drug-induced liver damage in patients with tuberculosis who were being treated with a combination of 4 anti-tuberculosis medications (isoniazid, rifampin, pyrazinamide, and ethambutol.)
  • N-Acetyl Cysteine
    In patients being treated with a combination of drugs for tuberculosis (including isoniazid), supplementation with N-acetylcysteine (600 mg twice a day) reduced the amount of liver damage caused by the drugs.
  • Probiotics

    A common side effect of antibiotics is diarrhea, which may be caused by the elimination of beneficial bacteria normally found in the colon. Controlled studies have shown that taking probiotic microorganisms-such as Lactobacillus casei, Lactobacillus acidophilus, Bifidobacterium longum, or Saccharomyces boulardii-helps prevent antibiotic-induced diarrhea.

    The diarrhea experienced by some people who take antibiotics also might be due to an overgrowth of the bacterium Clostridium difficile, which causes a disease known as pseudomembranous colitis. Controlled studies have shown that supplementation with harmless yeast-such as Saccharomyces boulardii or Saccharomyces cerevisiae (baker's or brewer's yeast)-helps prevent recurrence of this infection.

    Treatment with antibiotics also commonly leads to an overgrowth of yeast (Candida albicans) in the vagina (candida vaginitis) and the intestines (sometimes referred to as "dysbiosis"). Controlled studies have shown that Lactobacillus acidophilus might prevent candida vaginitis.

  • Vitamin C

    Tooth discoloration is a side effect of minocycline observed primarily in young children, but it may occur in adults as well. Vitamin C supplementation may prevent staining in adults taking minocycline.

  • Picrorhiza

    Picrorhiza (Picrorhiza kurroa) is an herb from India with well-established anti-inflammatory and liver protective actions. Use of a combination formula known as Liv.100 that contains picrorhiza protected animal livers against damage caused by isoniazid and other antituberculosis antibiotics.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Support Medicine

  • Bromelain

    When taken with amoxicillin, bromelain was shown to increase absorption of amoxicillin in humans. When 80 mg of bromelain was taken together with amoxicillin and tetracycline, blood levels of both drugs increased, though how bromelain acts on drug metabolism remains unknown. An older report found bromelain also increased the actions of other antibiotics, including penicillin, chloramphenicol, and erythromycin, in treating a variety of infections. In that trial, 22 out of 23 people who had previously not responded to these antibiotics did so after adding bromelain taken four times per day.

    Doctors will sometimes prescribe enough bromelain to equal 2,400 gelatin dissolving units (listed as GDU on labels) per day. This amount would equal approximately 3,600 MCU (milk clotting units), another common measure of bromelain activity.

  • Probiotics
    In one study, taking 500 mg of Saccharomyces boulardii twice daily enhanced the effectiveness of the antibiotic vancomycin in preventing recurrent clostridium infection. Therefore, people taking antibiotics who later develop diarrhea might benefit from supplementing with saccharomyces organisms.
  • Licorice

    The potent anti-inflammatory substance known as glycyrrhizin from licorice has been combined with isoniazid for treatment of tuberculosis. An older study found a benefit from combining the two compared to using isoniazid alone. Glycyrrhizin was given by injection, so it is not certain if licorice extracts containing glycyrrhizin would be as effective given by mouth. The treatment required at least three months of administration.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Reduces Effectiveness

  • Khat

    Khat (Catha edulis) is an herb found in East Africa and Yemen that has recently been imported into the United States. Studies have shown that chewing khat significantly reduces the absorption of ampicillin, which might reduce the effectiveness of the antibiotic. Therefore, people taking ampicillin should avoid herbal products that contain khat.

  • Magnesium

    Taking calcium, iron, magnesium, or zinc at the same time as minocycline can decrease the absorption of both the drug and the mineral. Therefore, calcium, iron, magnesium, or zinc supplements, if used, should be taken an hour before or after the drug.

  • Zinc

    Taking calcium, iron, magnesium, or zinc at the same time as minocycline can decrease the absorption of both the drug and the mineral. Therefore, calcium, iron, magnesium, or zinc supplements, if used, should be taken an hour before or after the drug.

Potential Negative Interaction

  • Foods with Histamines

    Isoniazid has some monoamine oxidase inhibitor (MAOI) activity. Isoniazid can alter metabolism of tyramine-containing foods, leading to reactions associated with MAOI drugs (diarrhea, flushing, sweating, pounding chest, dangerous changes in blood pressure, and other symptoms). People taking isoniazid should avoid tyramine-containing foods. Isoniazid can also alter metabolism of histamine-containing foods, leading to headaches, sweating, pounding chest, flushing, diarrhea, low blood pressure, and itching. People taking isoniazid should avoid histamine-containing foods (such as tuna, sauerkraut juice, or yeast extract).

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Foods with Tyramine

    Isoniazid has some monoamine oxidase inhibitor (MAOI) activity. Isoniazid can alter metabolism of tyramine-containing foods, leading to reactions associated with MAOI drugs (diarrhea, flushing, sweating, pounding chest, dangerous changes in blood pressure, and other symptoms). People taking isoniazid should avoid tyramine-containing foods. Isoniazid can also alter metabolism of histamine-containing foods, leading to headaches, sweating, pounding chest, flushing, diarrhea, low blood pressure, and itching. People taking isoniazid should avoid histamine-containing foods (such as tuna, sauerkraut juice, or yeast extract).

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Explanation Required 

  • Barberry

    Berberine is a chemical extracted from goldenseal (Hydrastis canadensis), barberry (Berberis vulgaris), and Oregon grape (Berberis aquifolium), which has antibacterial activity. However, one double-blind study found that 100 mg berberine given with tetracycline (a drug closely related to doxycycline) reduced the efficacy of tetracycline in people with cholera. In that trial, berberine may have decreased tetracycline absorption. Another double-blind trial found that berberine neither improved nor interfered with tetracycline effectiveness in cholera patients. Therefore, it remains unclear whether a significant interaction between berberine-containing herbs and doxycycline and related drugs exists.

  • Vitamin K

    Several cases of excessive bleeding have been reported in people who take antibiotics. This side effect may be the result of reduced vitamin K activity and/or reduced vitamin K production by bacteria in the colon. One study showed that people who had taken broad-spectrum antibiotics had lower liver concentrations of vitamin K2 (menaquinone), though vitamin K1 (phylloquinone) levels remained normal. Several antibiotics appear to exert a strong effect on vitamin K activity, while others may not have any effect. Therefore, one should refer to a specific antibiotic for information on whether it interacts with vitamin K. Doctors of natural medicine sometimes recommend vitamin K supplementation to people taking antibiotics. Additional research is needed to determine whether the amount of vitamin K1 found in some multivitamins is sufficient to prevent antibiotic-induced bleeding. Moreover, most multivitamins do not contain vitamin K.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers' package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.