DR-TB HIV Coordinator: Isoniazid (H) Mono/Poly DR-TB Regimen

Regimen, Duration and Dosage for Isoniazid [H] Mono/Poly DR-TB Regimen

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Isoniazid (H) mono/ poly Drug-resistant TB (DR-TB) regimen has the following regimen, duration and dosage of drugs.

Regimen: (6 or 9) Lfx R E Z

Dosage

The dosage of drugs would vary as per the weight of the patients.
Adult patients (≥ 18 years) would be classified in weight bands of <16 kg, 16-29 kg, 30-45 kg, 46-70 kg and 70 kg. The drug dosages by these weight bands are shown in the table below.
All drugs in the regimen are to be given on a daily basis under observation.

Table: Drugs used in H Mono/ Poly DR-TB Regimen by Weight bands for Adults. *Source: Guidelines for PMDT, India, 2021, p79.*
SR. NO	DRUGS	16-29 KG	30-45 KG	46-70 KG	>70 KG
1	Rifampicin (R)	300 mg	450 mg	600 mg	750 mg
2	Ethambutol (E)	400 mg	800 mg	1200 mg	1600 mg
3	Pyrazinamide (Z)	750 mg	1250 mg	1750 mg	2000 mg
4	Levofloxacin (Lfx)	250 mg	750 mg	1000 mg	1000 mg

Duration

H mono/ poly DR-TB regimen is for 6 or 9 months with no separate Intensive Phase (IP)/ Continuation Phase (CP).
In exceptional situations of unavailability of loose drug R or E or Z, the use of 4 FDC (HREZ) with Levofloxacin (Lfx) loose tablets may be considered as an option rather than not starting the H mono/ poly DR-TB patients on treatment.

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Isoniazid [H] Mono/Poly DR-TB Regimen: Pre-treatment Evaluation

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Pre-treatment evaluation for any TB patient must include a thorough clinical evaluation by a doctor with:

History and physical examination
Height/ weight check
Random Blood Sugar (RBS)
Chest X-ray
HIV test

No additional investigations (except the basic evaluations mentioned above) are required for Isoniazid (H) mono/ poly Drug-resistant TB (DR-TB) patients unless clinically indicated.

The pre-treatment evaluation carried out at the time of treatment initiation can be considered valid for 1 month from the date of the test result and the patient can be reinitiated on a subsequent regimen considering the previously conducted pre-treatment tests.

Active Drug Safety Management and Monitoring (aDSM) treatment initiation form needs to be completed for all DR-TB patients at the time of initiation of each new episode of the treatment.

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Adverse Drug Events: H Mono/Poly DR-TB Regimen

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he potential adverse drug events that can occur when using drugs in the H mono/ poly DR-TB regimen are tabulated below:

Table: Possible Adverse Events due to Drugs in H Mono/ Poly DR-TB Regimen; *Source: Guidelines for PMDT, India, 2021, p83.*
ADVERSE DRUG EVENTS	SUSPECTED DRUG(S)
Hepatitis	Rifampicin (R), Pyrazinamide (Z)
QT prolongation	Fluoroquinolone (FQ), Clofazimine (Cfz)
Rash, allergic reaction and anaphylaxis	Any drug
Gastrointestinal symptoms	Z, Ethambutol (E), Cfz, FQs
Giddiness	FQ, Z
Arthralgia	Z, FQ
Peripheral neuropathy	FQ, E
Depression	FQ
Psychotic symptoms	FQ
Seizures	FQ
Tendonitis and tendon rupture	FQ
Vestibular toxicity (tinnitus and dizziness)	FQ
Optic neuritis	E, Linezolid (Lzd), Cfz
Metallic taste	FQ
Superficial fungal infection and thrush	FQ

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Replacement Sequence in the H Mono/Poly DR-TB and Shorter Oral Bdq-containing MDR/RR-TB Regimens

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Different conditions may demand the replacement of Isoniazid (H) mono/ poly Drug-resistant TB (DR-TB) and shorter oral Bedaquiline (Bdq)-containing Multidrug-resistant (MDR)/ Rifampicin-resistant (RR) -TB regimens.

Replacement Sequence of Drugs in H Mono/ Poly DR-TB Regimen

Drugs of the H mono/ poly DR-TB regimen will be replaced in case of:

Additional resistance to one of the drugs in the regimen
Intolerance to any of the drug/s used in the regimen
Unavailability of one of the drug
Contraindication of the component drugs of the regimen

In such situations, modification of H mono/ poly DR-TB regimen may be done using the sequence of using replacement drugs as delineated in the table below.

Table: Replacement Sequence of Drugs to Modify the H mono/ poly DR-TB Regimen
SITUATION	SEQUENCE OF USING REPLACEMENT DRUGS
If Levofloxacin (Lfx) can’t be used	Replace with High dose Moxifloxacin (Mfx^h) if second line-line probe assay pattern suggests. Do liquid culture drug susceptibility testing for detection of resistance to Mfx^h, Pyrazinamide (Z), Linezolid (Lzd) and Clofazimine (Cfz)
If Mfx^h or Z can’t be used	Replace with Lzd. If Lzd also cannot be given, replace it with Cfz* + Cycloserine (Cs).
If both Mfx^h and Z can’t be used	Add 2 drugs of the 3 – Lzd, Cfz*, Cs in order of preference based on resistance, tolerability & availability.
If Rifampicin (R)-resistance exists	Switch to an appropriate shorter or longer regimen.
*whenever Drug Susceptibility Test (DST) is available.

In the first three situations above, treatment will continue for a total duration of 9 months.
Treatment duration of H mono/ poly DR-TB regimen can be longer in extensive pulmonary TB diseases up to 9 months.
The use of new drugs is not yet recommended in the treatment of H mono/ poly DR-TB cases due to lack of evidence.

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Replacement Sequence of Drugs in Shorter Oral Bdq-containing MDR/RR-TB Regimen

If there is a need for stopping/ replacing any drug in the shorter oral Bedaquiline-containing multi-drug resistant (MDR)/rifampicin-resistant tuberculosis (RR-TB) regimen then this regimen needs to be stopped.
Evaluate the patient to switch to a longer oral Multi (M)/ Extensively Drug-resistant TB (XDR-TB) regimen.
Replacement/ stopping any of the drugs in the regimen is not recommended.

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