ISONIAZID (H)

Anti-tuberculosis antibacterial

Dosage Forms

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Tablet

50 mg
100 mg

Fixed Drug Combinations (FDC) tablet

Ethambutol 400 mg + isoniazid 150 mg
Rifampicin 60 mg + isoniazid 30 mg
Rifampicin 75 mg + isoniazid 50 mg
Rifampicin 150 mg + isoniazid 75 mg
Rifampicin 300 mg + isoniazid 150 mg
Rifampicin 60 mg + isoniazid 30 mg + pyrazinamide 150 mg
Rifampicin 70 mg + isoniazid 50 mg + pyrazinamide 150 mg
Rifampicin 150 mg + isoniazid 75 mg + ethambutol 400 mg + pyrazinamide 275 mg

Uses

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  • Tuberculosis
  • Prophylaxis against tuberculosis in exposed infants

Dose and Duration

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Intensive phase in TB treatment (in combination with rifampicin, ethambutol, and pyrazinamide)

Give once daily for 2 or 3 months as in table below

Adult and child over 12 years:

Weight (kg) Isoniazid (mg)
30–37 150
38–54 225
55–70 300
>70 375

Child < 12 years:

Weight (kg) Isoniazid (mg)
4–7 50
8–11 100
12–15 150
16–24 200
>25 Use adult formulation
Continuation phase in TB treatment

Give once daily as in table below; for 4 months with rifampicin, or for 6 months with ethambutol

Adult and child over 12 years:

Weight (kg) Isoniazid (mg) with Rifampicin Isoniazid (mg) with Ethambutol
30–37 150 300
38–54 225 300
55–70 300 300
>70 300 450

Child below 12 years:

Weight (kg) Isoniazid (mg) with Rifampicin
4–7 50
8–11 100
12–15 150
16–24 200
>25 Use adult formulation
Prophylaxis against tuberculosis in exposed infants

5 mg/kg once daily for 6 months

Contraindications

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  • Severe liver disease

Side Effects

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  • Stomach upset, dry mouth
  • Nerve pain in hands and legs
  • Liver disorders
  • Blood disorders
  • Allergic reactions

Interactions

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  • Phenytoin (increased effect of phenytoin)
  • Carbamazepine (increased risk of liver toxicity)

Patient Instructions

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  • Preferably take on empty stomach
  • Avoid taking alcohol while on treatment
  • Report immediately to the health worker if any yellowing of the skin or eyes, nausea, vomiting, feeling of sickness, or tingling pain in the hands or legs occur
  • Take the anti-TB medicines at the same time each day

Pregnancy

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  • Can be used

Breast-feeding

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  • Can be used

⚠️ Caution

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  • To prevent nerve pain, give pyridoxine 10 mg daily
  • If the patient shows signs of liver toxicity, discontinue treatment until symptoms resolve