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 Guide Editors
 Editor In Chief
    Joel E. Gallant, MD, MPH

Pharmacology Editor
    Paul Pham, PharmD, BCPS

Zambia Guideline Team
   Peter Mwaba MMed PhD FRCP
   Alywn Mwinga MMed
   Isaac Zulu MMed MPH
   Velepie Mtonga MMed
   Albert Mwango MBChB
   Jabbin Mulwanda MMed FCS
 

 

 

Drugs>Antimicrobial Agents>
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Isoniazid

Paul A. Pham Pharm.D. and John G. Bartlett M.D.
05-27-2009

Zambia Specific Information

  • Available formulation in Zambia: Isoniazid tablet: 100-300 mg. Tablet (scored): 50 mg. Isoniazid + ethambutol tablet: 150 mg + 400 mg. Rifampicin + isoniazid tablet: 60 mg + 30 mg; 150 mg + 75 mg; 300 mg + 150 mg. 60 mg + 60 mg (For intermittent use 3 times weekly). 150 mg + 150 mg (For intermittent use 3 times weekly). Rifampicin + isoniazid+ ethambutol tablet: 150 mg + 75 mg + 275 mg. Rifampicin + isoniazid+ pyrazinamide tablet: 60 mg + 30 mg + 150 mg; 150 mg + 75 mg + 400 mg. 150 mg + 150 mg + 500 mg (For intermittent use 3 times weekly). Rifampicin + isoniazid+ pyrazinamide+ ethambutol tablet: 150 mg + 75 mg + 400 mg + 275 mg.
  • All new TB cases (smear positive, smear negative, extra-pulmonary TB, and smear negative relapse): INH, RIF, PZA, and EMB x 2 months, then INH plus EMB x 6 months.
  • TB smear positive re-treatment cases (e.g treatment failure, treatment after default, smear positive relapse): INH, RIF, PZA, EMB, and SM x 2 months, then INH, RIF, PZA, and EMB x 6 months.
  • May increase risk of peripheral neuropathy  with d4T co-administration.

REFERENCES

Zambia Information Author: Paul A. Pham, Pharm. D.

INDICATIONS

FDA

  • Treatment and prevention of TB

FORMS

brand 
name
 
generic 
Mfg 
brand 
forms
 
cost* 
IsoniazidIsoniazid (INH)Generic manufacturers (Barr, Eon and others)oral
tablet
100 mg; 300 mg
$0.09; $0.34
      oral
syrup
50 mg/5 mL (16 oz)
$58.00
Nydrazid INHGenevaIM
vial
100 mg/ml (10ml)
$24.90
Rifamate INH 150 mg/rifampin (RIF) 300 mgAventisoral
capsule
INH 150 mg/RIF 300 mg
$3.71
Rifater INH 50 mg/RIF120 mg/(PZA) 300 mgAventisoral
capsule
INH 50 mg/RIF 120 mg/pyrazinamide(PZA) 30 mg
$2.32

*Prices represent cost per unit specified and are representative of "Average Wholesale Price" (AWP). AWP Prices were obtained and gathered by Lakshmi Vasist Pharm D using the Red Book, manufacturer's information, and the McKesson database.

^Dosage is indicated in mg unless otherwise noted.

USUAL ADULT DOSING

  • Treatment of latent TB (prophylaxis): INH 5 mg/kg (max 300 mg) PO once-daily x 9 mos or DOT: 15 mg/kg (max 900 mg) 2x/wk x 9 mos
  • Active TB treatment (with other anti-TB agents): 5 mg/kg (max 300 mg) PO once-daily x 6-9 mos or directly observed therapy (DOT): 15 mg/kg (max 900 mg) 2-3x/wk x6-9 mos
  • Active TB treatment continuation phase (with other anti-TB agents):3x/wk for CD4 <100
  • Active TB treatment duration: 6 mos for most forms except severe cavitary pulmonary (9 mos), bone/joint (9 mos), miliary (9 mos), CNS (9-12 mos)
  • Coadminister with pyridoxine 50 mg/d or 100 mg 2x/wk to prevent neuropathy.
  • DOT preferred for active TB in all pts
  • Obtain CBC and LFTs at baseline and periodically throughout course of therapy. Monitor monthly for hepatitis Sx; consider monthly LFTs in pts with other risks for hepatotoxicity.
  • Administer 1 hr before or 2 hrs after meals.

RENAL DOSING

DOSING FOR GLOMERULAR FILTRATION OF 50-80

Usual dose

DOSING FOR GLOMERULAR FILTRATION OF 10-50

Usual dose

DOSING FOR GLOMERULAR FILTRATION OF <10 ML/MIN

If slow acetylator use 150 mg PO once-daily; HD:5 mg/kg post-dialysis

DOSING IN HEMODIALYSIS

5 mg/kg post-dialysis

DOSING IN PERITONEAL DIALYSIS

Once-daily dose post dialysis (50% of dose if slow acetylator)

DOSING IN HEMOFILTRATION

No data

ADVERSE DRUG REACTIONS

COMMON

  • Increased transaminases:increased ALT in 10-20% (D/C if LFTs >5x ULN)
OCCASIONAL

  • GI intolerance (diarrhea with liquid INH; crushed tabls typically better tolerated in infants/children)
RARE

  • Clinical hepatitis in 0.6% and fatal hepatitis in 0.02% (risk increased with age, alcohol, prior liver disease, concurrent RIF, and pregnancy). May occur even after mos on treatment. In most cases, enzyme levels return to normal with discontinuation of therapy. Recommend monthly clinical and lab monitoring. Instruct pts to report sxs of hepatitis. D/C if sxs or signs of hepatic damage. Consider non/less hepatotoxic alternatives. Reinstitute only after sxs and lab abnormalities resolved. Restart with gradual dose escalation. Withdraw with any indication of recurrent liver damage.
  • Peripheral neuropathy and optic neuropathy (dose-related and prevented by pyridoxine co-administration)
  • Hypersensitivity reaction (rash, exfoliative dermatitis, urticaria, and edema.)
  • Fever
  • CNS toxicity: psychosis
  • Arthralgia
  • Bone marrow suppression

DRUG INTERACTIONS

  • Phenytoin: may increase phenytoin levels. Monitor closely.
  • Carbamazepine: may increase carbamazepine levels. Monitor closely.
  • Enflurane: in rapid acetylators of INH, high output renal failure may occur. Monitor closely.
  • Rifampin: possible additive hepatotoxicity due to production of secondary pathway metabolite of INH (hydrazine and isonicotinic acid). Consider rifabutin.
  • Warfarin:may increase INR, monitor closely
  • Antacids:may decrease INH absorption (avoid co-administration)
  • Tyramine rich foods (wine, cheese, etc):- may develop monoamine poisoning (avoid tyramine rich foods)
  • Ketoconazole: may decrease ketoconazole levels (based on case reports, clinical significance unknown).
  • Theophylline: serum level may be increased. Dose may need to be decreased.
  • Ethionamide: may increase INH serum level. Monitor for toxicity (peripheral neuritis and hepatotoxicity) with co-administration.
  • Cycloserine: may increase central nervous system adverse effects. Monitor closely and discontinue if severe.
  • Benzodiazepines (i.e diazepam, triazolam, midazolam): may increase benzodiazepine serum levels. Consider using oxazepam or lorazepam with INH co-administration.
  • Prednisone and prednisolone: may decrease INH serum levels. Monitor INH for therapeutic efficacy.
  • Ethanol: avoid.

SPECTRUM

Detailed Spectrum of Activity

PHARMACOLOGY

Pharmacology

COMMENTS

First line agent for treatment and prophylaxis of TB. Because of high prevalence of INH resistance, treatment with RIF-containing regimen should be strongly considered in the treatment of latent TB for immigrants from Vietnam, Haiti, and Philippines [NEJM 2002;347:1850].

REFERENCES

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