AVP and pneumothorax: Various medical conditions should be considered in relation to SIADH, including [2]: 1) ectopic secretion of ADH (released from tumor tissue, infections, or conditions with altered intrathoracic pressure, such as with a pneumothorax or status asthmaticus); 2) increased hypothalamic production of ADH-like substances associated with neurological disorders (infections, Guillain-Barre syndrome, and brain tumors); 3) medications (cytotoxic agents, carbamazepine, chlorpropamide, clofibrate, narcotics, and sulfonylurea); and 4) administration of exogenous ADH or oxytocin.