Snapshot A 67-year-old man who is a long time smoker is brought to the emergency room following a seizure episode. He has no previous seizure history and according to his wife, no clear precipitating factor triggered the event. The seizure lasted a total of 2 minutes but the patient had no head trauma. A routine laboratory panel demonstrates signficiant hyponatremia. A computed tomography scan shows a speculated lesion within the right lung. (SIADH secondary to small cell lung cancer) Overview Describes a group of drugs used in the treatment of various disorders affecting the hypothalamus and/or pituitary Anti-Diuretic Hormone (ADH) Antagonists Mechanism of action selectively blocks the action of ADH at the V2 receptor, which are expressed peripherally and is involved in the modulation of kidney function allows for aquaresis and increased sodium concentration examples include conivaptan, tolvaptan, lixivaptan, mozavaptan, and satavaptan Clinical use euvolemic hyponatremia (e.g., SIADH) hypervolemic hyponatremia (e.g., CHF) Adverse effects increased thirst and dry mouth weakness nausea/vomitting Desmopressin Acetate Mechanism of action anti-diuretic that binds to V2 receptors at the renal collecting duct, leading to increase in aquaporin channels and thus water reabsorption from the urine also stimulates the release of von Willebrand factor (vWF) from endothelial cells via the V2 receptor Clinical use central diabetes insipidis sleep enuresis von Willebrand disease Adverse effects facial flushing headaches hyponatremia that can lead to seizures gastrointestinal upset Growth Hormone Mechanism of action recombinant form of growth hormone (GH), which stimulates growth, cell reproduction, and regeneration (anabolic effects) increases the production of insulin-growth factor-1 (IGF-1) Clinical use replacement therapy for patients with GH deficiency Turner syndrome allows for height growth in children with conditions associated with short stature chronic renal failure Prader-Willi syndrome short bowel syndrome Adverse effects headaches edema myalgia gynecomastic scoliosis Leuprolide Mechanism of action acts as a mimetic of gonadotrophin-releasing hormone (GnRH), leading to the secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH) and subsequent increases in estradiol and testosterone levels Clinical use idiopathic central precocious puberty prostate cancer breast cancer endometriosis uterine fibroids Adverse effects hot flashes insomnia headaches unstable mood Oxytocin Mechanism of action neuropeptide that facilitates milk letdown, uterine contractions, and bonding via binding to its receptors receptors are expressed by neurons in many parts of the brain and spinal cord (e.g., amygdala) Clinical use labor stimulation uterine hemorrhage management milk let down Adverse effects cramping/stomach pain nausea/vomiting hypo/hypertension arrhythmias seizures Somatostatin (Octreotide) Mechanism of action octapeptide that mimics naturally occurring somatostatin, which is a potent inhibitor of growth hormone, glucagon, and insulin Clinical use acromegaly and gigantism bleeding esophageal varices carcinoid syndrome gastrinoma glucagonoma Adverse effects headache hypothyroidism cardiac conduction changes (e.g., bradycardia) gastrointestinal symptoms (e.g., cramping, diarrhea, or constipation)