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TB Drug Calculator

References and Disclaimer: MMWR 29 Jun 2018 67(25), pp723-6; 2018-2021 Report of the Committee of Infectious Diseases "Red Book," American Academy of Pediatrics; Clin Infect Dis, 2016 Aug 10 (epub ahead of print); MMWR 9 Dec 2011 60(48), pp1650-3 (+erratum); Am J Resp Crit Care Med, Vol 167 (2003), pp606-7 (+erratum). Program ©2007, 2010, 2012, 2014, 2016, 2018, 2020 Cameron Kaiser, MD, MPH.

This program, although based on published American Thoracic Society, Infectious Diseases Society of America and Centers for Disease Control guidelines for antituberculosis drug dosing, is not affiliated with or endorsed by the CDC, the IDSA, the AAP, the ATS or its membership, and should not be used to replace appropriate clinical judgment or expert consultation with a physician experienced in the management of TB cases. This application is distributed in the hope that it will be useful, but without any express or implied warranty, including regarding merchantability or fitness for a particular purpose. You alone are solely responsible for any error committed, or any misapplication of data presented.

Instructions (READ FIRST!): This dosing calculator generates typical doses for most anti-tuberculosis drugs, based on and rounded to closest known available standard strengths (such as capsules, elixirs, tablets, etc.) and capped at suggested maximums. mg/kg is provided. IV/IM doses are rounded to the nearest quarter-volume for ease in administration and pill splitting is not assumed by this calculator except if "scored" is listed for pediatric dosing; thus, very small doses may be difficult to achieve with standard available strengths and doses that should require cross-checking to avoid potential overdoses are flagged in bold red. In these cases, more precise dosing or pharmacy consultation is recommended, especially for neonates or very young children. Similarly, medications, or dosing administrations, under conditions requiring expert consultation before proceeding are not computed and simply shown with a CONSULT recommendation instead.

Ethionamide, PAS and cycloserine doses below are target doses. These medications should be ramped and divided doses are strongly advised. This calculator does not compute streptomycin or clofazamine doses.

In individuals with low blood levels, it is sometimes possible to dose (in particular) INH, RIF and fluoroquinolones much higher than the doses suggested here. For example, INH doses of 600mg daily and RIF 900-1800mg daily may be well tolerated by some adults, and even low-weight individuals may tolerate standard INH and RIF doses without weight adjustment. This calculator does not consider this situation and low drug levels should prompt expert pharmacist or clinician consultation.

For individuals weighing less than 40kg (88lb), the calculator will use pediatric values; pediatric patients over 40kg should be dosed as adults according to the ATS, which is observed by this calculator. You may force pediatric or adult dosing; see the dosage report generated to change settings.

This revised version of the Drug Calculator strongly advises daily dosing, with triweekly dosing an option for HIV-negative individuals who are expected to adhere well to treatment, are smear-negative and have non-cavitary disease. Biweekly dosing (same dose) is still permissible but discouraged as missing a single dose makes it effectively once-weekly dosing, which is inferior.

The Calculator also computes rifapentine (RPT) doses in compliance with guidelines for latent (LTBI) treatment with isoniazid/rifapentine as released by the US CDC. INH/RPT treatment for LTBI is best administered only to eligible HIV-negative patients over 2 years of age, preferably via directly observed therapy (DOT), or supervised self-administration if DOT is infeasible.

Drug selection and length of treatment are not addressed by this calculator and should be based on local protocol, resistance profile, coincident medical comorbidity and clinical presentation. Only daily and triweekly dosing is computed for the most common drugs I use locally; if you have other suggestions, please send me your comments.

Weight (IBW if possible):

Drug dosages computed for:
first line: isoniazid (INH), rifampin (RIF), ethambutol (EMB), pyrazinamide (PZA), rifabutin (RFB), rifapentine (RPT) (LTBI only);
second/third line: levofloxacin and moxifloxacin; amikacin/kanamycin, capreomycin, ethionamide (ETH), p-aminosalicylic acid (PAS), cycloserine (CS), linezolid (LZ)

Cameron Kaiser, MD, MPH