Pharmacotherapy considerations
Anti-TB medications kill mycobacteria, thereby preventing further complications of
early primary disease and progression of disease. However, disappearance of
caseous or granulomatous lesions does not occur even with therapy. These drugs
are classified as first-line and second-line drugs. First-line drugs have less toxicity
with greater efficacy than second-line drugs. All first-line agents are bactericidal with
the exception of ethambutol.
First-line agents include
rifampin
,
isoniazid
(INH),
pyrazinamide
,
ethambutol
,
and
streptomycin
. Second-line agents
are
capreomycin
,
ciprofloxacin
,
cycloserine
,
ethionamide
,
kanamycin
,ofloxacin,
levofl
oxacin
, and para-aminosalicylic acid.
INH and rifampin are effective against bacilli in necrotic foci and intracellular
populations of mycobacteria. Streptomycin, aminoglycosides, and capreomycin have
poor intracellular penetration. Multidrug-resistant (MDR) TB is defined as resistance
to at least INH and rifampin (see Multidrug-Resistant TB). The emergence of drug-
resistant strains has necessitated the use of second-line agents.
Naturally drug-resistant organisms occur with a frequency of approximately 10
-6
;
however, individual resistances may vary. The resistance to streptomycin is 10
-5
, to
INH is 10
-6
, and to rifampin is 10
-8
. The chance that an organism is naturally resistant
to both INH and rifampin is on the order of 10
-14
. Because populations of this size do
not occur in patients, organisms naturally resistant to 2 drugs are essentially
nonexistent. If only a single medication is administered to a patient with TB, the
subpopulations susceptible to that medication are destroyed, but the other
categories continue to multiply. Thus, the use of multiple agents in the treatment of
TB is essential.
Adverse drug effects
Adverse effects of isoniazid (INH) (eg, hepatitis) are rare in children; therefore,
routine determination of serum aminotransferase levels is not necessary. Consider
monthly monitoring of hepatic function tests in the following patients: (1) those with
severe or disseminated TB; (2) those with concurrent or recent hepatic disease; (3)
those receiving high daily doses of INH (10 mg/kg/d) in combination with rifampin,
pyrazinamide, or both; (4) women who are pregnant or within the first 6 weeks
postpartum; (5) those with clinical evidence of hepatotoxic effects; and (6) those with
hepatobiliary tract disease from other causes.
Bed rest
The advisability of bed rest varies with the type and severity of the disease. No
limitation of activity is required in patients with TB infection or asymptomatic primary
pulmonary TB. Severely ill patients with miliary TB, TB meningitis, or disseminated
TB may require complete bed rest; these individuals may also need transfer to the
intensive care unit until their condition is stabilized.
Consultations
An infectious diseases consultation may be helpful in managing affected patients.
Treatment of Pulmonary TB
Recommendations for the treatment of pulmonary tuberculosis (TB) include a 6-
month course of isoniazid (INH) and rifampin, supplemented during the first 2
months with pyrazinamide. Ethambutol (or streptomycin in children too young to be
monitored for visual acuity) may need to be included in the initial regimen until the
results of drug susceptibility studies are available.
Drug susceptibility studies may not be required if the risk of drug resistance is not
significant. Significant risk factors include residence in a community with greater
than 4% primary resistance to INH, history of previous treatment with anti-TB drugs,
history of exposure to a drug-resistant case, and origin in a country with a high
prevalence of drug resistance. The purpose of this recommendation is to decrease
the development of multidrug-resistant (MDR) TB in areas in which primary INH
resistance is increased.
Another treatment option is a 2-month regimen of INH, rifampin, and pyrazinamide
daily, followed by 4 months of INH and rifampin twice a week. Effective treatment of
hilar adenopathy when the organisms are fully susceptible is a 9-month regimen of
INH and rifampin daily or a 1-month regimen of INH and rifampin once a day,
followed by 8 months of INH and rifampin twice a week.
Because poor adherence to these regimens is a common cause of treatment failure,
directly observed therapy (DOT) is recommended for treatment of TB. DOT means a
healthcare provider or other responsible person must watch the patient ingest the
medications. Intermittent regimens should be monitored by DOT for the duration of
therapy, because poor compliance may result in inadequate drug delivery.
Another initiative recently launched by the World Health Organization (WHO) is the
DOTS-plus strategy, which is based on finding appropriate treatment strategies for
MDR TB and drug susceptibility testing, as well as judicious usage of second-line
drugs.
[15, 16]
This initiative also focuses on community involvement and a good
recording and reporting system.
Treating Extrapulmonary TB
Most cases of extrapulmonary tuberculosis (TB), including cervical
lymphadenopathy, can be treated with the same regimens used to treat pulmonary
TB. Exceptions include bone and joint disease, miliary disease, and meningitis. For
these severe forms of drug-susceptible disease, the recommendation is a regimen
of 2 months of isoniazid (INH), rifampin, pyrazinamide, and streptomycin once a day,
followed by 7-10 months of INH and rifampin once a day.
Another recommended regimen is 2 months of INH, rifampin, pyrazinamide, and
streptomycin, followed by 7-10 months of INH and rifampin twice a week.
Streptomycin may be administered with initial therapy until drug susceptibility is
known. Consider administering capreomycin or kanamycin instead of streptomycin
in patients who may have acquired TB in areas in which resistance to streptomycin
is common.
Managing TB With HIV Coinfection
Optimal therapy for tuberculosis (TB) in children with human immunodeficiency virus
(HIV) infection has not been established. According to the guidelines provided by the
Centers for Disease Control and Prevention (CDC), effective treatment of TB for
patients infected with HIV should include directly observed therapy (DOT) and
consultation with a specialist.
A regimen that uses
rifabutin
instead of rifampin has been advised when
simultaneously treating HIV disease and TB. This situation may occur (1) when
antiretroviral treatment is recommended for a newly diagnosed HIV infection in a
patient with active TB or (2) when a patient with active TB has established HIV
infection and continuation of antiretroviral therapy is recommended. This
recommendation is based on the fact that the use of rifampin with protease inhibitors
or nonnucleoside reverse transcriptase inhibitors is contraindicated.
The treatment regimen for TB should initially include at least 3 drugs and should be
continued for at least 9 months. Isoniazid (INH), rifampin, and pyrazinamide with or
without ethambutol or streptomycin should be administered for the first 2 months.
Treatment of disseminated disease or drug-resistant TB may require the addition of
a fourth drug (see Multidrug-Resistant TB).
Multidrug-Resistant TB
Infection caused by multidrug resistant (MDR) organisms, defined as organisms
resistant to at least isoniazid (INH) and rifampin, has reached critical levels
worldwide. The median prevalence of resistance to any of the 4 antituberculosis
(TB) drugs in an update by the World Health Organization (WHO) and the
International Union Against Tuberculosis and Lung Disease (IUATLD) was reported
to be 10.2% (range 0-57.1%).
[16, 17]
The diarylquinoline antimycobacterial, bedaquiline (Sirturo), was approved by the
FDA in December 2012 as part of a 22-week multidrug regimen for pulmonary MDR-
TB. Approval was based on phase 2 data that showed bedaquiline significantly
improved time to sputum culture conversion and included 2 consecutive negative
sputum cultures collected at least 25 days apart during treatment. At week 24,
sputum culture conversion was observed in 77.6% of patients in the bedaquiline
treatment group compared with 57.6% of patients in the placebo treatment group.
[18,
19]
In another phase 2 study, researchers found bedaquiline (TMC207) added to
standard therapy for MDR-TB reduced the time to conversion to a negative sputum
culture compared with placebo and increased the proportion of patients with
conversion of sputum culture (48% vs 9%).
[20]
Provisional guidelines from the Centers for Disease Control and Prevention (CDC)
include use of bedaquiline for FDA-approved and off-label uses. In addition to the
approved indication as part of at least a 4-drug regimen for treatment of MDR-TB,
the guidelines include use on a case-by-case basis for children, HIV-infected
persons, pregnant women, persons with extrapulmonary MDR-TB, and patients with
comorbid conditions on concomitant medications when an effective treatment
regimen cannot otherwise be provided.
[21]
Categories of TB drug resistance
Primary and secondary resistance are 2 categories of drug resistance recognized.
Primary resistance is defined as the occurrence of resistance to anti-TB treatment in
an individual who has no history of previous treatment. Secondary resistance
involves the emergence of resistance during the course of ineffectual anti-TB
therapy.
In 2006, the WHO Global Task Force defined another category of MDR TB termed
extensively drug-resistant (XDR) TB.
[2]
This is defined as resistance to first-line
drugs, including resistance to at least rifampicin and isoniazid (INH), in addition to
resistance to any fluoroquinolone and at least one of following second-line anti-TB
drugs: capreomycin, kanamicin, and
amikacin
. This usually occurs as a result of
mismanagement of MDR TB.
Risk factors for TB drug resistance
Risk factors for the development of primary drug resistance include patient contact
with drug-resistant contagious TB, residence in areas with a high prevalence of
drug-resistant M tuberculosis, birth outside the United States, ethnicity other than
non-Hispanic white, young age, human immunodeficiency virus (HIV) infection, and
the use of intravenous drugs. Secondary drug resistance reflects patient
nonadherence to the regimen, inappropriate drug regimens, and/or interference with
absorption of the drug.
MDR TB management principles
Guidelines endorsed by the Centers for Disease Control and Prevention (CDC) state
that if a child is at risk of or has disease resistant to INH, then at least 2 drugs to
which the isolate is susceptible should be administered. Another important
management principle is to never add a single drug to an already failing regimen.
The resistance pattern, toxicities of the drugs, and patients' responses to treatment
determine duration and the regimen selected.
The initial treatment regimen for patients with MDR TB should include 4 drugs. At
least 2 bactericidal drugs (eg, INH, rifampin), pyrazinamide, and either streptomycin
or another aminoglycoside (also bactericidal) or high-dose ethambutol (25 mg/kg/d)
should also be incorporated into the regimen.
Six-month treatment regimens are not advocated for patients with strains resistant to
INH or rifampin. Intermittent therapy with twice-a-week regimens is also not
recommended. In isolated INH resistance, the 4-drug, 6-month regimen should be
initially started for the treatment of pulmonary TB. INH should be discontinued when
resistance is documented. Continue pyrazinamide for the entire 6-month course of
treatment.
In the 9-month regimen, INH should be discontinued upon the documentation of
isolated INH resistance. If ethambutol was included in the initial regimen, continue
treatment with rifampin and ethambutol for a minimum of 12 months. If ethambutol
was not included, then repeating susceptibility tests is advocated, as are
discontinuation of INH and the addition of 2 new drugs (eg, ethambutol and
pyrazinamide).
Resistance to both INH and rifampin presents a complex problem that often
necessitates consultation with a specialist. Continuing the initial drug regimen (with 2
drugs to which the organism is susceptible) until bacteriologic sputum conversion is
documented is preferable; then administer at least 12 months of 2-drug therapy. The
role of new agents such as quinolone derivatives and amikacin in MDR cases
remains unclear.
Neonates With Household Contacts With TB
The American Academy of Pediatrics (AAP) and Centers for Disease Control and
Prevention (CDC) guidelines advocate avoidance of separation of the mother and
infant, if possible. Authorities have endorsed recommendations regarding different
clinical scenarios.
Mother with a positive TST result and no evidence of current disease
Because the positive tuberculin skin test (TST) result may be evidence of an
unrecognized case of contagious tuberculosis (TB) within the household, careful
screening and evaluation of the other members of the household should be
performed. Perform a Mantoux test when the infant is aged 4-6 weeks and 3-4
months. Consider administration of isoniazid (INH) (10 mg/kg/d) to the infant if the
family cannot be promptly tested.
Mother has current disease but is noncontagious at delivery
In this situation, separation of the mother and infant is not necessary, and the
mother can breastfeed the infant. Evaluation of the infant includes chest radiography
and Mantoux test at age 4-6 weeks; if the Mantoux test is negative, a repeat test is
warranted at ages 3-4 months and 6 months. INH should be administered even if the
TST result and chest radiography do not suggest TB, because sufficient cell-
mediated immunity (CMI) to prevent progressive disease may not develop until age
6 months.
Mother has current disease and is contagious at delivery
In this situation, separation of the mother and infant is recommended until the
mother is noncontagious. The rest of the management is the same as for the mother
with current disease but who is noncontagious at delivery.
Mother with hematogenous spread
Congenital TB is possible in this scenario. Promptly perform a Mantoux test and
chest radiography, and immediately begin treatment for the infant. INH should be
administered until the infant is aged 6 months, at which time evaluation of the infant
with a TST should be repeated. If the TST result is positive, the infant should be
treated with INH for a total of 9 months.
Surgical Management of TB
Pulmonary resection in patients with tuberculosis (TB) may be required in drug-
resistant cases because of the high likelihood of failure of the medication regimen.
Surgical resection may also be required in patients with advanced disease with
extensive caseation necrosis. Hemoptysis, although rare in children, may
necessitate surgical intervention. TB abscesses and bronchopleural fistulae also
should be surgically removed.
Complications of TB Disease
Miliary disease and tubercular (TB) meningitis are the earliest and most deadly
complications of primary TB. A high index of suspicion is required for prompt
diagnosis and management of these conditions. Pulmonary complications include
the development of pleural effusions and pneumothorax. Complete obstruction of a
bronchus can result if caseous material extrudes into the lumen. This can lead to
atelectasis of the involved lung. Bronchiectasis, stenosis of the airways,
bronchoesophageal fistula, and endobronchial disease caused by penetration
through an airway wall are other catastrophes that may occur with primary TB.
Perforation of the small bowel, obstruction, enterocutaneous fistula, and the
development of severe malabsorption may complicate TB of the small intestine.
Pericardial effusion can be an acute complication or can resemble chronic
constrictive pericarditis.
Renal complications including hydronephrosis and autonephrectomy usually do not
occur in children. Paraplegia may complicate Pott disease of the spine (ie, TB
spondylitis) (see
Pott Disease [Tuberculous Spondylitis]
).
Outcomes of TB Disease
The prognosis of tuberculosis (TB) varies according to the clinical manifestation.
Poor prognosis is associated with disseminated TB, miliary disease, and TB
meningitis.
The prognosis of TB meningitis varies according to the stage of the disease at the
time treatment is started (see TB Meningitis in Evaluation of Pediatric
Extrapulmonary TB). Stage 1 has a good prognosis, whereas patients with stage 3
usually have sequelae such as deafness, blindness, paraplegia, mental retardation,
movement disorders, and diabetes insipidus.
The US mortality rate from TB is about 0.6 deaths per 100,000 individuals, which
represents approximately 1,700 deaths per year and an annual mortality rate of
approximately 7% per newly identified case. In 1953, the mortality rate was 12.5
deaths per 100,000 individuals. This decrease in mortality is attributed to improved
health care and prompt initiation of therapy. However, multidrug-resistant TB cases
have a reported fatality rate of greater than 70%. Worldwide, deaths due to TB are
estimated to be 3 million per year.
Higher mortality rates occur in children younger than 5 years (20%) and in those
with a illness lasting longer than 2 months (80%).
Patient Surveillance
Public health authorities should be notified of all cases of tuberculosis (TB).
Directly observed therapy (DOT) is mandatory for the treatment of patients with
coexistent human immunodeficiency virus (HIV) disease, those with multidrug-
resistant (MDR) TB, and those who may be noncompliant.
A regular follow-up appointment every 4-8 weeks should be scheduled to ensure
compliance and to monitor the adverse effects of and response to the medications
administered. Adherence to the regimen is of vital importance to its success.
Therefore, every measure should be taken to provide language-specific and
culturally appropriate material to ensure compliance. Clear and written instructions
regarding the timing of medication and the quantity to be administered should be
provided.
Monitoring of liver function test results is not indicated routinely. However, it may be
required in the treatment of patients with miliary TB, TB meningitis, and coexistence
of other hepatic disorders or with concomitant hepatotoxic drug therapy. In the rare
event the patient has symptoms of hepatitis, discontinue the regimen and evaluate
liver function. If the tests are normal or return to normal, then a decision to restart
the medications may be made. Reintroduce the drugs one by one.
Follow-up chest radiography may be performed after 2-3 months of therapy to
observe the response to treatment in patients with pulmonary TB. However, hilar
lymphadenopathy may take several years to resolve. Thus, a normal chest
radiography finding is not required for termination of therapy.
Prevention of TB Disease
The key method of preventing tuberculosis (TB) is prompt identification and
treatment of patients with TB. Other strategies include patient education, treatment
of latent infection, and vaccination.
The World Health Organization (WHO) launched the Stop TB strategy in 2006
(modelled after the directly observed theraphy [DOT] strategy) and the core
components include pursuing high-quality DOT expansion and enhancement;
addressing TB and human immunodeficiency (HIV) infection, multidrug-resistant
(MDR) TB, and other challenges; contributing to health system strengthening;
engaging all care providers; empowering people with TB; and enabling and
promoting research.
[2]
Patient education
Thoroughly educate patients regarding compliance to therapy, adverse effects of
medications, and follow-up care.
Treatment of latent TB infection
Recommendations for preventive therapy are based on a comparative analysis of
the risk of administration of isoniazid (INH) versus the risk of acquiring the disease.
Adults with a positive tuberculin skin test (TST) result and no clinical or radiographic
manifestations who are receiving INH therapy have been demonstrated to have 54-
88% protection against the development of the disease, whereas children have been
shown to have 100% protection.
The risk of acquisition of TB is particularly high in very young children (< 5 y) and in
the adolescent population. Thus, patients in these age groups with a positive TST
result and no other manifestations should receive INH therapy. Active TB should be
carefully excluded before the initiation of preventive therapy.
For recent contacts of patients with contagious TB (ie, in the past 3 mo), INH
therapy is indicated even if the TST result is negative. This is especially true for
contacts who are infected with HIV or for household contacts younger than 5 years.
Household contacts of any age should be considered for INH therapy if they are
from a high-prevalence area, even if the TST result is negative.
The recommendations from the American Academy of Pediatrics (AAP) are to
administer 9 months of therapy. The drug of choice is INH. A treatment period of 12
months is recommended for patients with HIV infection. For the management of
contacts of INH-resistant cases, rifampin is recommended for 6 months in children.
In case of a high probability of infection with MDR TB, observation is recommended,
because none of the other drugs have been evaluated for preventive therapy.
Several drugs have been used in these circumstances, including pyrazinamide,
fluoroquinolones, and ethambutol, depending on the susceptibility patterns.
Vaccination
The
bacille Calmette-Guérin (BCG) vaccine
is available for the prevention of
disseminated TB. BCG is a live vaccine prepared from attenuated strains of M bovis.
The major role of BCG vaccination is the prevention of serious and life-threatening
disease such as disseminated TB and TB meningitis in children. The BCG vaccine
does not prevent infection with M tuberculosis.
Although the BCG vaccine has been in use since 1921 and approximately 3 billion
doses have been administered, its efficacy continues to be debated. Several trials
have been performed to assess the efficacy of the vaccine, and results vary.
However, 2 meta-analyses of the various trials concluded that the vaccine is
efficacious against miliary and meningeal TB.
[22]
Controversy surrounds the efficacy
of BCG vaccination against pulmonary TB.
The WHO’s Expanded Program on Immunization recommends the administration of
BCG at birth. The vaccine is used in more than 100 countries. In the United States,
BCG vaccination is currently recommended only in certain situations, including the
following:
Child has negative HIV and TST results, is exposed to persons with
contagious MDR (resistant to INH and rifampin) pulmonary TB, and cannot be
removed from the exposure
Child has negative HIV and TST results, is exposed to persons with untreated
or ineffectively treated contagious pulmonary TB, and cannot be removed from the
exposure or treated with anti-TB medication
From birth to age 2 months, administration of BCG does not require a previous TST.
Thereafter, a TST is mandatory before vaccination.
Adverse reactions due to the vaccine include subcutaneous abscess formation and
the development of lymphadenopathy. Rare complications, such as osteitis of the
epiphyses of the long bones and disseminated TB, may necessitate administration
of anti-TB therapy, except for pyrazinamide.
Contraindications to the administration of the vaccine include immunosuppressed
conditions such as primary or secondary immunodeficiency, including steroid use
and HIV infection. However, in areas of the world where the risk of TB is high, the
WHO recommends using the BCG vaccine in children who have asymptomatic HIV
infection.
Special Considerations
Tuberculosis (TB) presents a potential health hazard to the public; therefore, public
health authorities should be notified of all cases of TB.
Legal measures have been initiated in several states in the United States that allow
for civil or criminal detention of patients with active TB disease and persistent
noncompliance with directly observed therapy (DOT).
TB can cause significant morbidity in the pregnant woman and the fetus; hence,
pregnant women must be carefully evaluated and be placed on prophylaxis or
treatment as indicated. Hematogenous spread of the bacilli through the umbilical
vein and the placenta to the fetal liver or aspiration of tubercle bacilli from infected
amniotic fluid may lead to the development of congenital TB.
First-line agents recommended by the American Academy of Pediatrics (AAP)
include isoniazid (INH), rifampin, and ethambutol. No significant teratogenicity on the
fetus has been observed. Streptomycin is contraindicated, because it may lead to
the development of deafness in the fetus. Data regarding the use of pyrazinamide,
cycloserine, and ethionamide are not available; avoid these drugs if possible.
Treatment should be started as soon as the diagnosis of TB is confirmed or after the
first trimester in women younger than 35 years with recent tuberculin skin test (TST)
conversion. Strict adherence to the treatment protocol is essential to prevent the
development of congenital TB and maternal morbidity.
Breastfeeding should not be discouraged, because the amount of drug in breast milk
is very small, and no adverse effects have been documented. All pregnant women
on INH therapy should receive pyridoxine.
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