600 mg twice a week for pulmonary TB. She completed 2 months of therapy with isoniazid, rifampin,
TB and its treatment to the mother and the fetus? Are these drugs teratogenic?
Although concerns about the use of any medication during pregnancy always exist,
it is now recognized that untreated TB represents a far greater risk to a pregnant
woman and her fetus than the treatment.
66 TB is one of the leading nonobstetric
179 The World Health Organization recommends that
treatment of TB in pregnant women should be the same as that for nonpregnant
Isoniazid, rifampin, pyrazinamide, and ethambutol
are not teratogenic in humans.
In the United States, pyrazinamide is not
recommended for use during pregnancy because of insufficient safety data.
pyrazinamide is not included in the initial treatment regimen, the minimal duration of
33 All pregnant women receiving isoniazid should also receive
pyridoxine 25 mg/day because of the possibility of peripheral neuropathy.
Streptomycin should not be used during pregnancy except as a last alternative
because it has been associated with mild-to-severe ototoxicity in the fetus.
Ototoxicity can occur throughout the gestational period and is not confined to the first
trimester. With the exception of streptomycin ototoxicity, the occurrence of birth
defects in women being treated for TB with the above agents is no greater than that of
183 Therefore, administration of antituberculosis drugs is
not an indication for termination of pregnancy.
33 Because E.F. likely became pregnant
after completing the first 2 months of therapy, she should continue her current regimen
for a total of 6 months because she received pyrazinamide as part of the initial
MULTIDRUG-RESISTANT TUBERCULOSIS IN PREGNANCY
Little is known about the efficacy and safety of second-line drugs for the treatment of
MDR-TB during pregnancy. Two reports with small numbers of patients have
suggested that treatment is effective with no adverse effects to mother or child.
In a study of seven women treated for MDR-TB during pregnancy, no obstetric
complications or perinatal transmission of MDR-TB was observed.
were cured, one experienced treatment failure, and one stopped therapy
184 No evidence of drug toxicity was seen among their children exposed
to second-line drugs in utero, although one child was diagnosed with MDR-TB.
There are no well-controlled studies with bedaquiline in pregnancy; therefore, the
drug should only be used in pregnancy if clearly needed. More data are needed, but
pregnancy should not be a limitation to the treatment of MDR-TB.
When the baby is born, E.F. may breast-feed while continuing her medication. Drug
concentrations in breast milk are minimal and do not provide sufficient quantities for
the treatment or prevention of TB in the nursing infant.
QUESTION 1: A.M., a 3-year-old African American boy, is suspected of having TB. His father has been
The incidence of TB in children younger than 15 years of age has declined from
1,660 cases (2.9/100,000 population) in 1993 to 460 cases (0.8/100,000 population)
10 Children commonly have active TB disease as a complication of the initial
infection with M. tuberculosis, and the disease is characterized by intrathoracic
adenopathy, middle and lower lung lobe infiltrates, and the absence of cavitation on
186 Because of the high risk of disseminated TB in infants and
children, treatment should be started as soon as the diagnosis of TB is suspected. In
general, regimens recommended for adults are also recommended for infants,
children, and adolescents, with the exception that ethambutol is not used routinely in
33 Ethambutol is often avoided because it is difficult to assess visual acuity
in children. A.M. should be started on isoniazid 10 to 15 mg/kg/day, rifampin 10 to
20 mg/kg/day, and pyrazinamide 15 to 30 mg/kg/day.
treat children with three drugs (rather than four) in the initial phase because the
bacillary population is usually lower than in an adult and it may be difficult for an
infant or child to ingest four drugs. If resistance is suspected, ethambutol 15 to 20
mg/kg/day or streptomycin 20 to 40 mg/kg/day should be added to the regimen until
susceptibility of the organism to isoniazid, rifampin, and pyrazinamide is known.
Pyridoxine is recommended for infants, children, and adolescents who are receiving
If resistance is not suspected and drug susceptibility is confirmed, A.M. should
receive the isoniazid, rifampin, and pyrazinamide daily for 8 weeks. He can then
continue to take the isoniazid and rifampin daily or 2 to 3 times a week (DOT) for an
additional 4 months. The dosage for isoniazid and rifampin in a 2 to 3 times a week
regimen would be 20 to 30 mg/kg/dose and 10 to 20 mg/kg/dose, respectively (Table
A.M. should be examined routinely for signs and symptoms of hepatitis. Although
antituberculosis medications are generally well tolerated in children, LFTs are
commonly 2 to 3 times the upper limit of normal during therapy. These are often
benign and transient; however, the incidence of hepatitis in children from isoniazid
with rifampin may be 4 to 6 times more common than in children receiving isoniazid
alone. Most hepatitis occurs within the first 3 months of therapy and generally is
associated with higher than recommended doses of isoniazid or rifampin.
Children and adolescents should be screened for risk factors for TB using a
questionnaire, and they should be skin tested with 5 TU of PPD if one or more risk
Insufficient data are available to recommend use of IGRAs in
children. Isoniazid for 9 months is recommended for treatment of latent TB in this
188 Daily rifampin for 6 months is an acceptable alternative, especially in
children who cannot tolerate isoniazid or those exposed to a source case whose
isolate was isoniazid resistant.
Extrapulmonary Tuberculosis and Tuberculous
Discuss the presentation and prognosis of tuberculous meningitis. How should R.U. be treated?
Tuberculous meningitis is only one of the extrapulmonary complications of
infection with M. tuberculosis.
Successful treatment of extrapulmonary TB can usually be accomplished in 6 to 9
months with an acceptable relapse rate.
189 Some forms, such as bone or joint TB,
miliary TB, or tuberculous meningitis, may require 9 to 12 months of therapy.
Because specimens for culture and susceptibility testing may be difficult or
impossible to obtain from a site, response to treatment must be based on clinical and
Tuberculous meningitis in older persons is usually caused by hematogenous
dissemination of the tubercle bacilli from a primary site, most commonly the lungs. In
its early stages, tuberculous meningitis often is confused with aseptic meningitis
because the Gram stain is negative. The most common symptoms of tuberculous
meningitis are headache, fever, restlessness, irritability, nausea, and vomiting. A
positive Brudzinski sign and neck stiffness may be present. As illustrated in R.U., the
CSF is usually turbid with increased protein and decreased glucose concentrations.
There is an increase in the CSF white blood cell count with a predominance of
lymphocytes. Culture of the CSF for M. tuberculosis may not be helpful because rates
of positivity for clinically diagnosed cases range from 25% to 70%.
recognition and treatment are essential for a favorable outcome. Thus, empirical
treatment before receipt of confirmatory culture and susceptibility results is common
in suspected tuberculous meningitis. Multiple-drug therapy should be used because
irreversible brain damage or death can occur as soon as 2 weeks after the onset of
infection (not clinical symptoms).
Treatment should be initiated in R.U. with daily administration of isoniazid 300 mg,
rifampin 600 mg, pyrazinamide 2,000 mg, and ethambutol 1,600 mg for the first 8
33 After this initial phase of treatment, R.U. should receive daily isoniazid and
rifampin for an additional 7 to 10 months, although the optimal duration of therapy is
In addition, because R.U. is older, pyridoxine 10 to 50 mg/day should be
given to prevent the occurrence of peripheral neuropathy from isoniazid. It should be
reiterated that rifampin can impart a red to orange color to the CSF.
Isoniazid readily penetrates into the CSF, with CSF concentrations reaching up to
100% of those in the serum. Rifampin is often included in tuberculous meningitis
regimens and may be associated with reduced morbidity and mortality; however,
even with inflammation, CSF concentrations of rifampin are only 6% to 30% of those
found in the serum. Ethambutol should be used in the highest dosage to achieve
bactericidal concentrations in the CSF because its CSF concentrations are only 10%
to 54% of those in the serum. Streptomycin penetrates into the CSF poorly even with
Corticosteroids in moderate-to-severe tuberculous meningitis appear to reduce
sequelae and prolong survival.
192 The mechanism for this benefit is likely owing to
reduction of intracranial pressure. Dexamethasone 8 to 12 mg/day (or prednisone
equivalent) for 6 to 8 weeks should be used and then tapered slowly after symptoms
192 Corticosteroids are likely indicated for R.U.
The pharmacokinetics of the drugs used to treat tuberculosis are highly variable and
depend on weight, sex, genetic traits, and underlying comorbidities. Subtherapeutic
concentrations may be associated with a delayed response to therapy, increased risk
of relapse, or acquired drug resistance. Several studies measured drug concentrations
in patients with slow clinical response to TB treatment and found subtherapeutic
concentrations for isoniazid, rifampin, ethambutol, and rifabutin in a substantial
percentage of patients evaluated.
In one study, time to sputum culture
conversion was longer in patients with low serum concentrations.
observational study, 2-hour plasma concentrations were measured in 35 patients, and
plasma concentrations were below the normal ranges in 71%, 58%, 46%, and 10%
of patients for isoniazid, rifampin, ethambutol, and pyrazinamide, respectively.
addition, 45% of patients had subtherapeutic concentrations for both isoniazid and
rifampin. Treatment failure occurred significantly more frequently when
concentrations of isoniazid and rifampin were below the normal ranges (p = 0.013)
and below the median 2-hour drug concentration achieved in the study (p = 0.005).
In 142 patients with active TB, poor long-term outcomes were predicted by a 24-
hour area under the concentration–time curve (AUC) ≤363 mg × hour/L for
pyrazinamide, ≤13 mg × hour/L for rifampin, and ≤52 mg × hour/L for isoniazid.
Poor outcomes occurred in 32/78 patients with at least one drug with an AUC below
these threshold values compared to 3/64 patients without any low AUCs (odds ratio
= 14.14; 95% CI 4.08–49.1). Low rifampin and isoniazid peak concentrations and
AUCs predicted acquired drug resistance in all cases.
Based on these studies, therapeutic drug monitoring may be useful in patients with
poor or slow clinical response to therapy and allow for dosage adjustment to achieve
therapeutic drug concentrations. Additional patients who may benefit from
therapeutic drug monitoring include those with severe disease, diabetes, HIV
infection, renal dysfunction, and hepatic dysfunction.
sample can be obtained to estimate the peak concentration for most drugs, whereas a
3-hour postdose blood sample would be needed for rifabutin.
sample at 6 hours postdose (7 hours for rifabutin) may also be obtained. Trough
concentrations for most agents are below the detection limit of the assays at the end
of a dosing interval and are not useful clinically.
collected in red-top test tubes and processed promptly because some drugs are not
stable at room temperature in blood or serum. Once the drug concentrations are
known, comparisons can be made to the normal ranges for each drug and doses
adjusted accordingly. However, normal ranges for drug concentrations have not been
studied in regard to clinical outcome, and optimal drug concentrations for clinical
and microbiologic efficacy are not known.
196 Although therapeutic drug monitoring
may provide useful information, clinicians must remember that serum concentrations
are only one factor among multiple factors affecting treatment outcomes.
A full list of references for this chapter can be found at
http://thepoint.lww.com/AT11e. Below are the key references and websites for this
chapter, with the corresponding reference number in this chapter found in parentheses
Society of America. Treatment of tuberculosis. Am J Respir Crit Care Med. 2003;167:603. (33)
Centers for Disease Control and Prevention. Reported tuberculosis in the United States 2014.
http://www.cdc.gov/tb/statistics/reports/2014/pdfs/tb-surveillance-2014-report.pdf. Accessed October
Getahun H et al. Latent Mycobacterium tuberculosis infection. N EnglJ Med. 2015;372:2127. (22)
observationalstudy. J Antimicrob Chemother. 2014;69:2841. (196)
tuberculosis with genomics. Clin Microbiol Rev. 2015;28:523. (55)
tuberculosis. Pharmacotherapy. 2014;34:1187. (157)
Centers for Disease Control and Prevention. Tuberculosis (TB). http://www.cdc.gov/tb
World Health Organization. Global tuberculosis report 2014.
http://www.who.int/tb/publications/global_report/gtbr14_main_text.pdf. Accessed September 22, 2015.
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