Antibiotics - Antimycobacterials: Nursing pharmacology

Definitions & Key takeaways

Mycobacterium is a genus of bacteria that includes many species that are pathogenic to humans. It's known to cause tuberculosis, leprosy, and some non-tuberculosis lung infections. Antimycobacterials are a class of antibiotics effective against mycobacterium species. The primary targets of antimycobacterial drugs are the enzymes that mycobacteria use to build their cell walls. Antimycobacterial drugs are typically administered in combination to target different enzymes and minimize bacterial resistance to these antibiotics.

The first-line antimycobacterials for tuberculosis include rifampin, isoniazid, pyrazinamide, and ethambutol. Second-line antimycobacterials include bedaquiline, cycloserine, ethionamide, rifabutin, aminosalicylic acid, capreomycin, and amikacin. There is also dapsone used to treat leprosy. There may be cases that are multidrug resistant, and these are treated with drugs like bedaquiline, capreomycin, cycloserine, and amikacin.

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Introduction0:00–0:33

Anti-mycobacterials are medications used to treat infections caused by the Mycobacterium species. These include tuberculosis, caused by Mycobacterium tuberculosis, leprosy, also known as Hansen's disease, caused by Mycobacterium leprae, and non-tuberculous lung infections caused by Mycobacterium avium complex or MAC, which includes Mycobacterium avium, Mycobacterium chimera, and Mycobacterium intracellulari.
Anti-mycobacterial drugs can be divided into two broad categories. We have the first line antimycobacterials, which are the standard initial therapy, and the second line anti-mycobacterials used when the first line drugs aren't suited, like when they have contraindications, they have failed to treat the infection, or with multi-drug resistant tuberculosis.

Antimycobacterials0:33–2:12

The first line antimycobacterials include isoniazid or INH for short, which is administered orally or intramuscularly, as well as streptomycin or SM, which is given intravenously or intramuscularly, rifampin or RIF, which is given orally and intravenously, and rifapentine or RPT, ethabutal or EMB, and pyrazinamide or PZA, all of which are given orally.
On the other hand, the second line antimycobacterials include bedaquiline, cycloserine, ethyanamide, rifabutin, and amino salicylic acid, all of which are administered orally, as well as capriomycin, which is administered intravenously or intramuscularly, and amicain, which can be administered intravenously, intramuscularly, or by inhalation.
These medications are mainly used for treating active mycobacterial infections, except rifabutin, which is preferred as preventative treatment against Mycobacterium avium complex in clients with advanced HIV infection who are severely immunocompromised.
Finally, antimycobacterials also include leprostatic medications such as dapsone, which is administered orally to treat leprosy.

Mechanism of action2:12–3:26

Now antimycobacterials have different mechanisms of action by targeting various mycobacterial structures. Issoniazid, ethabutal, aminosalicylic acid, etionomide, and cycloserine act mainly by disrupting the synthesis of essential components of the bacterial cell walls, which causes bacteria to burst out of osmotic pressure and die.
On the other hand, rifampin, rifapentine, and rifabutin work by inhibiting the bacterial DNA dependent RNA polymerase, which prevents the bacteria from synthesizing RNA, ultimately killing them.
Next, streptomycin, amicain, and capriomycin work by inhibiting bacterial ribosomes, stopping protein synthesis. There is also bedaquiline, which inhibits the synthesis of bacterial ATP, making them run out of energy needed for their metabolic functions and then ultimately die.
The mechanism of action of some medications like pyrazinamide isn't fully understood, but it is thought to interfere with bacterial fatty acid synthesis, which is needed for their growth.
Finally, dapsone works by inhibiting the pathway of folic acid, ultimately disrupting bacterial proliferation. Unfortunately, anti-mycobacterial medications can cause undesired side effects, ranging from mild side effects requiring dose adjustment and careful monitoring to serious organ damage, which can require immediate discontinuation.

Side effects3:26–6:00

Clients taking antimycobacterials may present with gastrointestinal side effects, which include nausea, vomiting, anorexia, stomach upset, and abdominal pain.
Other side effects include hypersensitivity reactions ranging from skin rashes or hives to life-threatening anaphylaxis.
This can occur with any of the antimycobacterial medications, but it is more commonly seen in isoniazid, rifampicin, pyrazinamide, etionamide, cycloserine, ethambutal, aminosalicylic acid, and streptomycin.
Some of these medications can also cause neurotoxicity, most often associated with isoniazid, which is associated with peripheral neuropathy, optic neuritis, memory impairment, and agitation, ethabuttal, which can cause optic neuritis, decreased visual acuity or color blindness, capriamycin and amicain, which have a boxed warning for odotoxicity.
Cycloserine, which can cause confusion, depression, psychosis, and seizures, thionamide, which can cause optic neuritis, as well as streptomycin, which has a boxed warning for neurotoxicity that can manifest as peripheral neuropathy, odotoxicity, and toxicity to the optic nerve.
Clients on antimycobacterials can also develop hepatotoxicity, which is a boxed warning for isoniazid. Next, bedaquiline has a boxed warning for QT prolongation.
Dapsone can cause hematological problems like hemolytic anemia, aplastic anemia, and agranulocytosis, while rifabutin can cause neutropenia.
Nephrotoxicity is a side effect of etambuttal and capriomycin and a boxed warning for amicain. Finally, rifampin, rifapentine, and rifabutin can turn certain body fluids like urine, tears, and saliva a reddish orange color.
As far as interactions with other medications are concerned, rifampin, rifapentine, and rifabutin are notable for their ability to induce a number of cytochrome P450 isoenzymes, meaning that by accelerating the metabolism of other medications, rifampin reduces the effectiveness of medications like warfarin, oral contraceptives, and medications used to treat HIV infection.

Contraindications and cautions6:00–6:58

Antim-mycobacterial medications should not be used with clients with severe hepatic or renal disease, alcoholism, complicated diabetes, and severe neurological dysfunction.
Additional precautions should be taken when administering antimycobacterial medications during pregnancy, breastfeeding, and to children or elderly clients.
Specifically, isoniazid and pyrazinamide are contraindicated in clients with liver disease and gout, whileetambutal is contraindicated in young children, unconscious clients, or any client who is unable to report visual changes.
Rifapentine is contraindicated in clients with porphyria, a condition in which the body has difficulty making heme, and aminosalicylic acid is contraindicated in clients with renal impairment.
Cycloserine is contraindicated in clients with a history of seizures, psychosis, excessive use of alcohol, or renal insufficiency.

Nursing considerations & client education6:58–10:21

All right. When caring for a client with tuberculosis who has been prescribed a treatment regimen consisting of isoniazid, rifampin, pyrazinamide, and etambutal, start by performing a baseline assessment, including weight, vital signs, lung sounds, SPO2, and current symptoms such as a productive cough, fatigue, night sweats, and anorexia.
Then review your client's most current laboratory test results, such as CBC, renal and liver function test results, Quantiferon TB gold plus test or QFT plus for short, T-Spot TB test or T-SOT for short, sputum smear and culture, as well as diagnostic test results like TB skin test, chest X-ray, and results of their ophthalmic examination.
Then explain to your client that these anti-mycobacterial medications will work together to help treat their infection. Instruct them to take all 4 medications consistently at the same time each day with a full glass of water and on an empty stomach, either 1 hour before or 2 hours after a meal.
Also, remind your client to drink plenty of fluids and avoid alcohol during treatment. Finally, emphasize the importance of taking their medications exactly as prescribed, highlighting the importance of adherence for treatment success and to prevent the development of bacterial resistance.
Next, let your client know about some side effects they could experience during treatment. Advise them that their urine, tears, or saliva may turn a reddish orange color.
Reassure them that this is harmless, but it can discolor soft contact lenses. Then let them know that gastrointestinal side effects like nausea and abdominal pain can be lessened by eating small, frequent meals throughout the day.
Teach your client that peripheral neuropathy that could present with numbness, tingling, or a burning sensation in their hands or feet is often a sign of vitamin B6 deficiency and should be reported to their healthcare provider right away.
Remind them to take the prescribed vitamin B6 supplement daily, as well as including dietary sources of the vitamin, such as chickpeas, salmon, tuna, bananas, potatoes, and fortified breakfast cereals.
Also remind them to take their folic acid supplement daily and to increase foods high in folate like dark green leafy vegetables, peanuts, and whole grains.
Prompt them to report to their healthcare provider right away if they experience symptoms of folic acid deficiency such as fatigue, agitation, or issues with memory.
Likewise, teach your client to report symptoms of hepatotoxicity, such as fatigue, abdominal pain, anorexia, dark urine, or yellowing of their eyes or skin, as well as symptoms of nephrotoxicity like decreased urine output, blood in the urine, or unusual weight gain.
Lastly, advise your client to see their optometrist if they experience symptoms of optic neuritis, such as decreased visual acuity and difficulty distinguishing colors.
Finally, during the course of treatment regimen, continue to monitor your client for side effects and evaluate for the desired therapeutic response, including a resolution of their tuberculosis symptoms, and absence of mycobacteria in their sputum.

Review10:21–11:07

All right. As a quick recap, antimycobacterials are medications used to treat infections caused by mycobacteria.
These include tuberculosis, leprosy, and some non-tuberculosis lung infections. First-line antimycobacterials commonly used to treat tuberculosis include isoniazid, rifampin, pyrazinamide, and habuttal.
When caring for a client on anti-mycobacterial treatment, nursing considerations include performing a baseline assessment, monitoring the client for side effects, and evaluating for desired therapeutic response.
Client teaching is focused on safe self-administration, medication adherence, as well as recognition of side effects that should be reported to their healthcare provider.
Antibiotics - Antimycobacterials: Video and Uses | Osmosis