Week 6 Nurse PHARMACOLOGY 676B

Week 6 Nurse PHARMACOLOGY 676B

Week 6 Nurse 676B

Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis, which typically affects the lungs. Tuberculosis is a major cause of morbidity and mortality globally. However, its incidence over the past decade has been declining (Adigun & Singh, 2022). For instance, the incidence rate worldwide was 132 cases per 100000 population while it was 2.8 per 100000 population in the US as of 2019 (Adigun & Singh, 2022). Despite this glimpse, the incidence of multidrug-resistant TB is on the rise. Additionally, this multisystemic condition predominantly affects respiratory, gastrointestinal, lymphoreticular, genitourinary, musculoskeletal, central nervous, and reproductive systems besides the liver and skin. TB as a disease has been explored enormously from its etiology to prognosis. The purpose of this paper is to discuss latent TB including its treatment with isoniazid based on the case scenario presented.

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Latent TB

According to Ilievska-Poposka et al. (2018), latent tuberculosis infection refers to a plight of sustained immune response stimulation by Mycobacterium tuberculosis antigens without manifestation of clinically active TB. It is estimated that one-quarter of the world’s population has latent TB (Ilievska-Poposka et al., 2018). This condition is asymptomatic as well as non-contagious with an estimated 5-10 % risk of reactivation during lifetime. Several risk factors for reactivation have been established and include immunosuppressed states such as HIV infection, chronic kidney disease, corticosteroid therapy, malignancy, diabetes mellitus, advanced age, and transplant with immunosuppressant use. Similarly, lifestyle factors such as smoking, heavy alcohol intake, intravenous drug abuse, malnutrition as well as preexisting lung diseases increase the likelihood of reactivation (Adigun & Singh, 2022). Consequently, diagnosis of latent TB provides a golden opportunity for treatment and subsequent prevention of reactivation. Finally, the condition is diagnosed via a tuberculin skin test or interferon-gamma release assay.

Treatment of Latent TB

A multitude of treatment options exists for the management of latent TB. These treatment options are per the National Tuberculosis Controllers Association and Centers for Disease Control and Prevention guidelines which recommend three rifamycin-based regimens and two alternatively daily isoniazid monotherapy regimens (Adigun & Singh, 2022). Rifamycin-based regimens include the following; isoniazid plus rifapentine once weekly for 3 months, a regimen recommended for children > 2 years and adults including those with HIV infection. Alternatively, daily rifampin for 4 months is strongly recommended in HIV adults and children of all ages while daily isoniazid plus rifampin for 3 months is preferred in children and adults of all ages including HIV positive individuals (Adigun & Singh, 2022). On the other hand, isoniazid-based therapy includes daily isoniazid for 6 months (strongly recommended in HIV negative adults and children of all ages and conditionally in HIV positive individuals of all ages) and daily isoniazid for 9 months (conditionally recommended for all individuals regardless of HIV infection status (Adigun & Singh, 2022). However, rifamycin-based treatment regimens are preferred to isoniazid-based monotherapy because of the shorter duration of treatment.

Following the aforementioned guidelines, Maria is likely to take Isoniazid daily for 6 months, a period which is strongly recommended in HIV-negative adults and children of all ages. From the case scenario, Maria has been off her medication for 1 month. However, according to the WHO operational handbook on tuberculosis Module 1: Prevention  (2018), Maria should continue with isoniazid for another 2 months to complete the original plan since she has taken less than 80% (approximately 66%) of doses expected in the regimen and the treatment course can still be completed within the expected time for completion, i.e. treatment duration + 33% additional time. Finally, Maria should be followed up monthly for liver function, physical and ophthalmologic exams (Madhuri Badrinath & John, 2021). Similarly, she should be advised on the importance of treatment adherence and a careful adherence plan to be devised.

Adverse Effects of Isoniazid

Isoniazid is an antimycobacterial agent that inhibits cell wall synthesis. Nevertheless, the agent has various side effects including hepatotoxicity, peripheral neuropathy, optic neuritis, pellagra, and metabolic acidosis (M. Badrinath & John, 2022). Isoniazid-induced peripheral neuropathy results from its metabolites that directly inhibit pyridoxine. Likewise, isoniazid directly inhibits pyridoxine phosphokinase which converts pyridoxine to its active form pyridoxine 5 phosphate. It manifests as numbness, tingling, and paresthesia thusPyridoxine is usually administered concurrently to counter these effects. Consequently, the production of GABA is reduced leading to seizures, psychosis, and even ataxia. Meanwhile, Isoniazid-induced hepatotoxicity is often insidious in onset ranging from 2 weeks to 6 months and predominantly affects adults more than 35 years. The symptomatology resembles viral hepatitis with prodromal manifestations such as nausea, fatigue, anorexia, right upper quadrant pain, dark urine, and jaundice (M. Badrinath & John, 2022). Therefore, Maria should be advised to notify the healthcare professional promptly in the event of the aforementioned manifestations.

Conclusion

In conclusion, diagnosis and treatment of latent TB prevent subsequent reactivation. Rifamycin-based regimens are preferred due to their shorter durations that enhance compliance. Isoniazid monotherapy should be closely be monitored for the onset of adverse effects including isoniazid-induced hepatitis and peripheral neuropathy. Finally, pyridoxine should be administered concurrently with isoniazid.

References

Adigun, R., & Singh, R. (2022). Tuberculosis. In StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK441916/

Badrinath, M., & John, S. (2022). Isoniazid Toxicity. https://pubmed.ncbi.nlm.nih.gov/30285383/

Badrinath, Madhuri, & John, S. (2021). Isoniazid Toxicity. In StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK531488/

Ilievska-Poposka, B., Metodieva, M., Zakoska, M., Vragoterova, C., & Trajkov, D. (2018). Latent tuberculosis infection – diagnosis and treatment. Open Access Macedonian Journal of Medical Sciences, 6(4), 651–655. https://doi.org/10.3889/oamjms.2018.161

WHO operational handbook on tuberculosis Module 1: Prevention. (2018). Who.Int. https://apps.who.int/iris/bitstream/handle/10665/331525/9789240002906-eng.pdf

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Maria is a 19-year-old exchange student from Brazil. She was started on daily isoniazid (INH) 4 months ago for latent tuberculosis (TB). She would like to be seen at your clinic now because it is closer to school. She has not taken her medication for 4 weeks and cannot recall when her labs were drawn last. She has no other health history and does not take any other medications. According to the national guidelines, how long would Maria likely need to take INH? Can she restart her medication even though she has been off for 1 month? How often should she be seen for follow-up? What are the black box warnings of INH?