There are two membranes that envelop the lungs. One lines the inner chest wall and is known as the parietal pleura. The other surrounds the lungs and is referred to as the visceral pleura. Normally about three to four teaspoons of fluid are spread thinly between these membranes to provide lubrication between these pleura. An excess amount of fluid that accumulates between these membranes, however, is a potentially dangerous condition known as a pleural effusion.
There are two general types of pleural effusion. A transudative pleural effusion is usually caused by abnormal lung pressure often due to congestive heart failure. Exudative effusions, on the other hand, are caused by inflammation of the pleura, often as the result of a lung disease such as pneumonia, lung cancer, tuberculosis, asbestosis (scarring of the lungs caused by inhaled asbestos fibers), sarcoidosis (a mysterious disorder that causes small lumps in different tissues and organs due to chronic inflammation), and drug reactions.
Drugs can cause pleural effusions secondarily as the result of a drug-induced disease such as drug-induced lupus pleuritis. In about 20 percent of cases, the cause of pleural effusion is unknown.
Drugs that have been associated with pleural effusion include:
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While symptoms of pleural effusion may include shortness of breath (dyspnea), a sharp chest pain, coughing, hiccups, and rapid breathing, pleural effusion can present no symptoms at all.
When presenting symptoms or when there is an increased risk of pleural effusion, the physician will listen to the patient’s breathing with a stethoscope and may tap on the chest to listen for dullness. To confirm a diagnosis, a chest x-ray, a thoracic CT scan, and/or an ultrasound may be performed. To determine the cause and type of pleural effusion, a thoracentesis (a sample of fluid is obtained by inserting a needle between the ribs) followed by pleural fluid analysis is undertaken.
Treatment may involve removal of the fluid, prevention of its re-accumulation, and/or addressing the underlying cause. In drug-induced cases, discontinuation of the offending drug often at least partially resolves the underlying pleural inflammation. But discontinuing the drug may be more difficult to implement than it may seem. Sometimes the offending drug may be critical in treating the underlying condition. Or several drugs are used and it may be difficult to identify the inducing agent.
Taking the characteristics and toxicity of the drugs into account may help in reaching a logical conclusion. But although there have been significant advances in the understanding of the mechanisms behind drug-induced toxicity, other factors that play a role in generating pleural changes remain unclear.