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isoniazid (Rx)Brand and Other Names:

 
 
 

Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablets

  • 50mg
  • 100mg
  • 300mg

oral syrup

  • 50mg/5mL

injectable solution

  • 100mg/mL
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Latent Tuberculosis Infection

Treatment of latent TB infection greatly reduces the risk that TB infection will progress to acitve disease

>30 kg: 300 mg PO qDay x9 months  

3-month regimen

  • Recommended for patients aged 12 years and older who are at high risk for developing TB disease including anyone who has had recent exposure to contagious TB, conversion from negative to positive on a test for TB infection, or a chest X-ray indicating prior TB disease
  • Persons with HIV who are otherwise healthy and not taking antiretrovirals may also use this regimen
  • 900 mg PO once weekly x3 months (administer with rifapentine 900 mg once weekly)
  • Administered as DOT
  • Not recommended for children <2 years, pregnant women or women planning to become pregnant, HIV-infected persons taking antiretrovirals, and patients whose TB infection is presumed to be the result of exposure to a person with TB disease that is resistant to 1 of the 2 drugs
  • References: CDC MMWR 2011;60:1650-3 and NEJM 2011;365:2155-2166

Active Tuberculosis Disease

5 mg/kg PO/IM qDay, not to exceed 300 mg qDay 

15 mg/kg PO/IM up; not to exceed 900 mg 1-3 times/week

Used in multi-drug regimen containing rifampin (or ribabutin or rifapentin), pyrazinamide, and ethambutol

Duration of treatment dependent on regimen consisting of an initial phase of treatment and a continutation phase of treatment

Note: Daily treatment has best results for HIV positive individuals

See Also Combos

With rifampin (Rifamate)

With rifampin and pyrizinamide (Rifater)

Other Indications & Uses

Newly infected patients

Household members and close associates of people recently diagnosed wtih TB

+ve TB skin test with +ve non-progressive chest x-ray

+ve TB skin test with underlying disease or immunosuppression

+ve TB skin test, <35 years old; >35 years old weigh use against risk of hepatitis

Dosage Forms & Strengths

tablets

  • 50mg
  • 100mg
  • 300mg

oral syrup

  • 50mg/5mL

injectable solution

  • 100mg/mL
more...

Latent Tuberculosis Infection

Treatment of latent TB infection greatly reduces the risk that TB infection will progress to acitve disease

10-15 mg/kg PO qDay; not to exceed 300 mg/day 

3-month regimen

  • Recommended for patients aged 12 years and older who are at high risk for developing TB disease including anyone who has had recent exposure to contagious TB, conversion from negative to positive on a test for TB infection, or a chest X-ray indicating prior TB disease
  • Use for children aged 2-11 years and patients with underlying conditions associated with TB should be considered on a case-by-case basis; preferred regimen for this age group is daily isoniazid for 9 months
  • Not recommended for children <2 years
  • >12 years: isoniazid 900 mg PO plus rifapentine 900 mg PO once weekly for 3 months
  • References: CDC MMWR 2011;60:1650-3 and NEJM 2011;365:2155-2166

Active Tuberculosis Disease

10-15 mg/kg PO qDay; not to exceed 300 mg/day OR  

20-30 mg/kg (up to 900 mg) 2 times/week

Used in multi-drug regimen

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Interactions

Interaction Checker

isoniazid and

No Results

     
     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Mild incr LFTs (10-20%)

            Peripheral neuropathy (dose-related incidence, 10-20% incidence with 10 mg/kg/d)

            Loss of appetite

            Nausea

            Vomiting

            Stomach pain

            Weakness

            1-10%

            Dizziness

            Slurred speech

            Lethargy

            Progressive liver damage (increases with age; 2.3% in pts > 50 yo)

            Hyperreflexia

            <1%

            Agranulocytosis

            Anemia

            Megaloblastic anemia

            Thrombocytopenia

            Systemic lupus erythematosus

            Seizure

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            Warnings

            Black Box Warnings

            Severe and sometimes fatal hepatitis may occur within the first 3 months of treatment and many months after treatment. Risk is related to age and increased with daily alcohol consumption.

            Patients should be instructed about signs and symptoms of hepatitis.

            Contraindications

            Prev INH hepatic injury or reaction; acute liver dz

            Hypersensitivity

            Cautions

            Alcohol or illicit injectable drug use, predisposition to neuropathy, malnourished, severe renal impairment, chronic liver dz

            Use w/ other anti-TB agents

            Give pyridoxine (B6) concurrently for pregnant women, malnourished pts. or those with neuropathic diathesis

            Alcohol use, renal or hepatic dysfunction will affect serum levels

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            Pregnancy & Lactation

            Pregnancy Category: C

            Lactation: distributed into milk but safe for nursing infants

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

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            Pharmacology

            Mechanism of Action

            Unknown: prob. inhibits cell-wall biosynthesis by interfering with lipid and DNA synthesis (bactericidal)

            Absorption

            Rapid and complete; rate can be slowed with food Peak Plasma Time: 1-2 hr

            Distribution

            All body tissues and fluids including CSF; crosses placenta; enters breast milk

            Protein Bound: 10-15%

            Metabolism

            Hepatic with decay rate determined genetically by acetylation phenotype

            Elimination

            Half-life elimination: fast acetylators: 30-100 min; slow acetylators: 2-5 hr; may be prolonged with hepatic or severe renal impairment

            Excretion: Urine (75-95%); feces

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            Administration

            IM Preparation

            At low temperatures, isoniazid in solution tends to crystallize; warm injection to room temperature to redissolve crystals prior to use

            IM Administration

            May be given by IM injection when oral therapy is not possible

            Storage

            Protect from light

            Store at <40°C, preferably between 15-30°C

            Protect from freezing

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            Images

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            Formulary

            FormularyPatient Discounts

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            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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