Ethambutol + Isoniazid

Ethambutol and Isoniazid are primarily used to treat tuberculosis, which is a serious infection that mainly affects the lungs but can also impact other parts of the body. Ethambutol is used in combination with other antituberculous drugs to treat active pulmonary tuberculosis, which means tuberculosis affecting the lungs. Isoniazid is used for both active tuberculosis and as a preventive therapy for latent tuberculosis infection, which is when the bacteria are present in the body but not causing symptoms, especially in individuals at high risk of developing active disease. Both medications are essential components of tuberculosis treatment regimens to prevent the development of drug resistance, which is when bacteria become resistant to the effects of the drugs used to treat them.

Ethambutol works by inhibiting the synthesis of the bacterial cell wall, which is the protective outer layer of the bacteria, specifically targeting actively growing Mycobacterium tuberculosis, the bacteria that cause tuberculosis. This action leads to impaired cell metabolism and cell death. Isoniazid inhibits the synthesis of mycolic acids, which are essential components of the bacterial cell wall, making it bactericidal, which means it kills bacteria, against actively growing Mycobacterium tuberculosis. Both medications disrupt the growth and multiplication of tuberculosis bacteria, but they act on different components of the bacterial cell wall, making them effective when used together in combination therapy.

For Ethambutol, the usual adult daily dose is 15 mg per kilogram of body weight, taken as a single oral dose once every 24 hours. In cases of retreatment, the dose may be increased to 25 mg per kilogram for the first 60 days, then reduced to 15 mg per kilogram. For Isoniazid, the usual adult daily dose is 5 mg per kilogram up to 300 mg daily in a single dose, or 15 mg per kilogram up to 900 mg per day, two or three times a week. Both medications are taken orally and are used in combination with other antituberculous drugs to prevent resistance and enhance efficacy, which means the ability to produce a desired or intended result.

Common side effects of Ethambutol include loss of appetite, upset stomach, and numbness or tingling in the hands or feet. Significant adverse effects include blurred vision and changes in color vision due to optic neuritis, which is inflammation of the optic nerve. Isoniazid may cause upset stomach, diarrhea, and more serious effects like liver damage, indicated by symptoms such as fatigue, nausea, and jaundice, which is yellowing of the skin and eyes. Both medications can cause peripheral neuropathy, which is damage to the nerves outside the brain and spinal cord, and patients should be monitored for any severe or persistent symptoms. Regular follow-up with healthcare providers is essential to manage and mitigate these side effects.

Ethambutol is contraindicated, which means it should not be used, in patients with known hypersensitivity, which is an allergic reaction, and those unable to report visual changes, as it can cause optic neuritis. Isoniazid carries a risk of severe liver damage, especially in patients with pre-existing liver conditions or those who consume alcohol regularly. Both medications require caution in patients with renal impairment, which is reduced kidney function, and should be used under close medical supervision. Regular monitoring of liver function and vision is essential to prevent serious adverse effects. Patients should be informed of the signs of liver damage and visual changes to report them immediately to their healthcare provider.