Introduction

This article explores treatment options for Mycobacterium avium complex (MAC) lung disease, which is a chronic lung disease caused by bacteria, the different triggers of the disease, and the most common symptoms seen inpatients. Mycobacterium avium complex, and the drug toxicity and medical adherence commonly associated with chronic diseases due to the prolonged use of medication such as antibiotics in the case of MAC lung disease. Managing and monitoring drug toxicity and medical adherence is vital to ensure effective treatment and the avoidance of negative side effects wherever possible. This disease is becoming a growing health concern, especially for older adults and people with weakened immune systems. If it is not managed properly—with the right treatment and careful monitoring of side effects—it can get worse and seriously impact a person’s health.

Understanding MAC Lung Disease, Triggers and Symptoms

MAC lung disease is the most common nontuberculous mycobacterial lung disease in the world. MAC stands for Mycobacterium avium complex - the group of organisms which cause MAC lung disease, which is noncontagious.¹ The MAC bacteria are naturally found in soil and water, and they have the potential to be an airborne bacterium if particles of soil or droplets of water are in the air. As a result, those who garden more or are outdoors more are more likely to be in contact with the bacteria.²

The disease is most common in the elderly, and other factors which are thought to trigger the progression of MAC lung disease are:

• Low body mass index
• Poor nutritional status
• Presence of cavitary lesions
• Extensive disease (broad or severe involvement of the lungs including bronchiectasis, chronic obstructive pulmonary disease, cystic fibrosis or emphysema)
• Immunocompromised
• Positive acid-fast bacilli smear

The most common symptoms of MAC lung disease include:

• Fatigue
• Chronic coughing with or without mucus
• Shortness of breath
• Excessive sweating/night sweats
• Coughing blood (haemoptysis)
• Weight loss
• Low-grade fever
• Chest pain³

Diagnosing MAC Lung Disease

MAC lung disease comes in two varieties: fibro-cavitary and nodular bronchiectasis. Nodular bronchiectasis occurs when the infection develops in the small airways and sacs. Without treatment, patients may experience more frequent episodes of bronchitis and pneumonia. Fibro-cavitary causes holes in the lung tissue, which can make individuals very susceptible to infection. This type of MAC lung disease requires immediate treatment.

Diagnosing MAC lung disease can pose a challenge, as its symptoms overlap with lots of different respiratory-related diseases, which can lead to misdiagnosis. Early and accurate diagnosis is essential to improve outcomes, and multiple diagnostic tests can help make an accurate decision.

To diagnose MAC disease and determine the type, a healthcare provider will perform a physical exam and ask questions about the symptoms the individual is experiencing. Sputum culture, bronchoscopy, and X-ray/computed tomography (CT) scan are examples of physical examinations. The X-ray/CT scan uses X-ray radiation, which gets absorbed by bones and dense tissues and can help highlight physical changes of the lung region. A sputum culture is a diagnostic test which involves collecting and analysing a sample of sputum, which is basically mucus or other materials that can be coughed up by the individual.⁴ Finally, bronchoscopy is a procedure where doctors insert a small tube with a camera attached on the end to view inside the lungs.⁵

Treatment for MAC Lung Disease

The course of treatment for MAC lung disease varies depending on the patient, the disease type, and its severity. One treatment is doing airway clearance or oxygen therapy to help maintain healthy blood oxygen levels. Antibiotics can be taken to directly cure the condition. The most common antibiotics used for the disease include macrolides, rifampin, and ethambutol, and these antibiotics work together to kill the bacteria and help clear any infection.⁶ The usual length of time for which the antibiotic should be taken is at least 15–18 months, which can seem like a long time, but it is to ensure that the medicine can reach deep inside every cavity and nodule within the lung to fully clear the infection. During this time, healthcare professionals would monitor the progress and most likely take sputum cultures to test if the infection is clearing up. From this information, more antibiotics may be prescribed.

Common Drug Toxicities in MAC Treatment

Drug toxicity refers to the degree at which a drug can cause harm to an individual, and this can be acute toxicity or chronic toxicity. Acute toxicity occurs from a single exposure, and chronic toxicity occurs over a prolonged period of time.⁷ Medication adherence can be defined as the extent to which a person’s behaviour corresponds with taking a medicine optimally.⁸ Understanding drug toxicity and adherence is crucial with MAC lung disease, as it requires long-term antibiotics which can cause side effects and poor adherence, which can affect treatment success. With the common antibiotics taken, there are certain toxicities associated with them.

Macrolides:

• Gastrointestinal upset⁹
• Hearing loss¹⁰
• Cardiac arrhythmia

Ethambutol:

• Optic neuritis (inflammation of the optic nerve)
• Visual disturbances (pain in eye, abnormal floaters, blurred vision, etc.)¹¹
• Skin rash
• Joint pain
• Fever
• Weak feeling in hands or feet

Rifamycins:

• Liver dysfunction
• Orange-red coloration of bodily fluids such as urine, sweat, and tears
• Low blood platelets
• Gastrointestinal disturbance¹²
• Constipation or diarrhea that is watery or bloody

Strategies to Manage Drug Toxicity

Managing drug toxicity is crucial to avoid side effects and to ensure that the medication is working well. One management technique is ongoing monitoring of drug use to identify early signs of toxicity. Older adults have a higher risk of medication complications because of narrow therapeutic windows and a higher likelihood of other medications being taken. This is important to consider with MAC lung disease, as it affects the elderly population more.¹³

Drug type, delivery, and amount need to be carefully considered, adjusted, and substituted if required depending on the specific individual—for example, the severity of the disease and patient size. A patient receiving too much medication can have a higher risk of toxicity, and too little can lead to poor success of the drug.¹⁴
To manage drug toxicity, the role of the pharmacist is also to monitor the other drugs the patient may be taking, especially since MAC lung disease is more prevalent in older people and they may have other health complications that need medication. Pharmacists must consider these other medications and ensure that additional medication to treat MAC lung disease won’t interfere with effectiveness or cause harm to the individual.

Challenges in Treatment Adherence

MAC lung disease is a chronic disease, and medical non-adherence is common among patients with chronic diseases. Medical non-adherence contributes to at least 100,000 preventable deaths and is unfortunately overlooked rather than recognized as a systemic issue. Potential barriers to medication adherence include patient-related barriers such as depression, drug or alcohol use, or cognitive impairment. Treatment-related barriers include complexity of treatment, inconvenience, time, and cost. Additionally, asymptomatic disease (a medical condition that does not currently cause any symptoms for some patients) can contribute to medical non-adherence, as it can create a low sense of urgency, so there is neglect with medication.¹⁵

Improving Adherence in MAC Lung Disease Treatment

Improving adherence for MAC lung disease involves adherence management according to barriers. With patient-associated barriers, it is important to fully educate them on important topics such as how drug and alcohol use can affect the effectiveness of their medication. Also, possibly therapy to help with depression and cognitive impairment, or even taking medication that will not interfere with the antibiotics. Healthcare professionals should regularly check on patients to ensure that antibiotics are being taken appropriately and monitor their adherence to ensure effectiveness.

Summary

In conclusion, drug toxicity and medical adherence are important considerations in certain diseases, including MAC lung disease. Treatment options for MAC include antibiotics—the most commonly used for this disease are macrolides, ethambutol, and rifamycin. There are also treatments which help alleviate symptoms, including airway clearance or oxygen therapy. As the antibiotics are taken for a prolonged period of time, there are associated risks with each antibiotic which need to be managed carefully by healthcare professionals. Two key ways to manage drug toxicity are by monitoring drug use and adjusting doses or substituting drugs. To improve drug adherence, it is important that patients are well educated on the effects of drugs and alcohol, and it is equally important that healthcare professionals regularly check patients and the response to treatment.