Guidelines for Treatment of Drug-Susceptible Tuberculosis and Patient Care
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TREATMENT OF TUBERCULOSIS Guidelines for treatment of drug-susceptible tuberculosis and patient care 2017 UPDATE Annex 6 ESSENTIAL FIRST-LINE ANTITUBERCULOSIS DRUGS TREATMENT OF TUBERCULOSIS Guidelines for treatment of drug-susceptible tuberculosis and patient care 2017 UPDATE Annex 6 ESSENTIAL FIRST-LINE ANTITUBERCULOSIS DRUGS Guidelines for treatment of drug-susceptible tuberculosis and patient care, 2017 update Contents: Web Annex 3: GRADE evidence profiles – Web Annex 4: Evidence-to-decision tables – Annex 5: Reports of the systematic reviews – Annex 6: Essential first-line antituberculosis drugs ISBN 978-92-4-155000-0 © World Health Organization 2017 Some rights reserved. This work is available under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 IGO licence (CC BY-NC-SA 3.0 IGO; https://creativecommons.org/licenses/by-nc-sa/3.0/igo). 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WHO/HTM/TB/2017.05 Contents Isoniazid 1 Rifampicin 3 Pyrazinamide 5 Ethambutol 7 iii GUIDELINES FOR TREATMENT OF DRUG-SUSCEPTIBLE TUBERCULOSIS AND PATIENT CARE - 2017 UPDATE Note For drug preparations (include fixed-dose combinations) and costs, see the Global Drug Facility web site: www.stoptb.org/gdf/drugsupply/drugs_available.asp. See also WHO Model Formulary 2017: http://www.who.int/selection_medicines/list/en iv ANNEX 6. ESSENTIAL FIRST-LINE ANTITUBERCULOSIS DRUGS Isoniazid General information Isoniazid, the hydrazide of isonicotinic acid, is highly bactericidal against replicating tubercle bacilli. It is rapidly absorbed and diffuses readily into all fluids and tissues. The plasma half-life, which is genetically determined, varies from less than one hour for fast acetylators to more than three hours for slow acetylators. Isoniazid is largely excreted in the urine within 24 hours, mostly as inactive metabolites. Clinical information Administration and dosage Isoniazid is normally taken orally but may be administered intramuscularly or intravenously to critically ill people. Adults: 5 mg/kg (4–6 mg/kg) daily Contraindications • Known hypersensitivity • Active, unstable hepatic disease (with jaundice) Precautions Clinical monitoring (and liver function tests, if possible) should be performed during the treatment of people with pre-existing liver disease. People at risk of peripheral neuropathy, as a result of malnutrition, chronic alcohol dependence, HIV infection, pregnancy, breastfeeding, renal failure or diabetes, should additionally receive pyridoxine, 10 mg daily. If the standard of health in the community is low, pyridoxine should be offered routinely. For established peripheral neuropathy, pyridoxine should be given at a dose of 50–75 mg daily. Since isoniazid interacts with the anticonvulsants used for epilepsy, the dosage of these drugs may have to be reduced during treatment with isoniazid. If possible, the serum concentrations of phenytoin and carbamazepine should be measured among people receiving isoniazid with or without rifampicin (see drug interactions below). Use in pregnancy Isoniazid is not known to be harmful in pregnancy. Pyridoxine supplementation is recommended for all pregnant (or breastfeeding) women taking isoniazid. 1 GUIDELINES FOR TREATMENT OF DRUG-SUSCEPTIBLE TUBERCULOSIS AND PATIENT CARE - 2017 UPDATE Adverse effects Isoniazid is generally well tolerated at recommended doses. Systemic or cutaneous hypersensitivity reactions occur occasionally during the first weeks of treatment. Sleepiness or lethargy can be managed by reassurance or adjusting the timing of administration. The risk of peripheral neuropathy is excluded if vulnerable people receive daily supplements of pyridoxine. Other less common forms of nervous system disturbance, including optic neuritis, toxic psychosis and generalized convulsions, can develop among susceptible individuals, especially in the later stages of treatment, and occasionally necessitate withdrawing isoniazid. Symptomatic hepatitis is an uncommon but potentially serious reaction that can usually be averted by promptly withdrawing treatment. More often, however, an asymptomatic rise in serum concentrations of hepatic transaminases at the outset of treatment is of no clinical significance and usually resolves spontaneously as treatment continues. A lupus-like syndrome, pellagra, anaemia and arthralgia are other rare adverse effects. Monoamine poisoning has been reported to occur after ingesting foods and beverages with high monoamine content, but this is also rare. Drug interactions Isoniazid inhibits the metabolism of certain drugs, which can increase their plasma concentration to the point of toxicity. Rifampicin, however, has the opposite effect for many of these drugs. For example, the available data indicate that administering both rifampicin and isoniazid reduces the plasma levels of phenytoin and diazepam. Isoniazid may increase the toxicity of carbamazepine, benzodiazepines metabolized by oxidation (such as triazolam), acetaminophen, valproate, serotonergic antidepressants, disulfiram, warfarin and theophylline. Overdosage Nausea, vomiting, dizziness, blurred vision and slurring of speech occur within 30 minutes to three hours of overdosage. Massive poisoning results in coma, preceded by respiratory depression and stupor. Severe intractable seizures may occur. Emesis and gastric lavage, activated charcoal, antiepileptics and intravenous sodium bicarbonate can be of value if instituted within a few hours of ingestion. Subsequently, haemodialysis may be of value. High doses of pyridoxine must be administered to prevent seizures. Storage Tablets should be kept in well-closed containers, protected from light. Solution for injection should be stored in ampoules, protected from light. 2 ANNEX 6. ESSENTIAL FIRST-LINE ANTITUBERCULOSIS DRUGS Rifampicin General information A semisynthetic derivative of rifamycin, rifampicin is a complex macrocyclic antibiotic that inhibits ribonucleic acid synthesis in a broad range of microbial pathogens. It has bactericidal action and a potent sterilizing effect against tubercle bacilli in both cellular and extracellular locations. Rifampicin is lipid-soluble. Following oral administration, it is rapidly absorbed and distributed throughout the cellular tissues and body fluids; if the meninges are inflamed, significant amounts enter the cerebrospinal fluid. A single dose of 600 mg produces a peak serum concentration of about 10 µg/ml in 2–4 hours, which subsequently decays with a half- life of 2–3 hours. It is extensively recycled in the enterohepatic circulation, and metabolites formed by deacetylation in the liver are eventually excreted in the faeces. Since resistance develops readily, rifampicin must always be administered in combination with other effective antimycobacterial agents. Clinical information