Treatment of GpS
Therapies for GpS can be viewed as the five D’s: Diet, Drug, Disruption, Devices, and Details.
Diet and nutrition: The mainstay treatment of GpS remains dietary modification. The most common recommendation is to limit meal size, often with increased meal frequency, as well as nutrient composition, in areas that may retard gastric emptying. In addition, some patients with GpS report intolerances of specific foods, such as specific carbohydrates. Nutritional consultation can assist patients with meals tailored for their current nutritional needs. Nutritional supplementation is widely used for patients with GpS.20
Pharmacological treatment: The next tier of treatment for GpS is drugs. Review of a patient’s medications is important to minimize drugs that may retard gastric emptying such as opiates and GLP-1 agonists. A full discussion of medications is beyond the scope of this article, but classes of drugs available include: prokinetics, antiemetics, neuromodulators, and investigational agents.
There is only one approved prokinetic medication for gastroparesis – the dopamine blocker metoclopramide – and most providers are aware of metoclopramide’s limitations in terms of potential side effects, such as the risk of tardive dyskinesia and labeling on duration of therapy, with a maximum of 12 weeks recommended. Alternative prokinetics, such as domperidone, are not easily available in the United States; some mediations approved for other indications, such as the 5-HT drug prucalopride, are sometimes given for GpS off-label. Antiemetics such as promethazine and ondansetron are frequently used for symptomatic control in GpS. Despite lack of positive controlled trials in Gp, neuromodulator drugs, such as tricyclic or tetracyclic antidepressants like amitriptyline or mirtazapine are often used; their efficacy is more proven in the functional dyspepsia area. Other drugs such as the NK-1 drug aprepitant have been studied in Gp and are sometimes used off-label. Drugs such as scopolamine and related compounds can also provide symptomatic relief, as can the tetrahydrocannabinol-containing drug, dronabinol. New pharmacologic agents for GpS include investigational drugs such as ghrelin agonists and several novel compounds, none of which are currently FDA approved.21,22
Fortunately, the majority of patients with GpS respond to conservative therapies, such as dietary changes and/or medications. The last part of the section on treatment of GpS includes patients that are diet and drug refractory. Patients in this group are often referred to gastroenterologists and can be complex, time consuming, and frustrating to provide care for. Many of these patients are eventually seen in referral centers, and some travel great distances and have considerable medical expenses.
Pylorus-directed therapies: The recent renewed interest in pyloric dysfunction in patients with Gp symptoms has led to a great deal of clinical activity. Gastropyloric dysfunction in Gp has been documented for decades, originally in diabetic patients with autonomic and enteric neuropathy. The use of botulinum toxin in upper- and lower-gastric sphincters has led to continuing use of this therapy for patients with GpS. Despite initial negative controlled trials of botulinum toxin in the pyloric sphincter, newer studies indicate that physiologic measures, such as the FLIP, may help with patient selection. Other disruptive pyloric therapies, including pyloromyotomy, per oral pyloromyotomy, and gastric peroral endoscopic myotomy, are supported by open-label use, despite a lack of published positive controlled trials.17
Bioelectric therapy: Another approach for patients with symptomatic drug refractory GpS is bioelectric device therapies, which can be delivered several ways, including directly to the stomach or to the spinal cord or the vagus nerve in the neck or ear, as well as by electro-acupuncture. High-frequency, low-energy gastric electrical stimulation (GES) is the best studied. First done in 1992 as an experimental therapy, GES was investigational from 1995 to 2000, when it became FDA approved as a humanitarian-use device. GES has been used in over 10,000 patients worldwide; only a small number (greater than 700 study patients) have been in controlled trials. Nine controlled trials of GES have been primarily positive, and durability for over 10 years has been shown. Temporary GES can also be performed endoscopically, although that is an off-label procedure. It has been shown to predict long-term therapy outcome.23-26
Nutritional support: Nutritional abnormalities in some cases of GpS lead to consideration of enteral tubes, starting with a trial of feeding with an N-J tube placed endoscopically. An N-J trial is most often performed in patients who have macro-malnutrition and weight loss but can be considered for other highly symptomatic patients. Other endoscopic tubes can be PEG or PEG-J or direct PEJ tubes. Some patients may require surgical placement of enteral tubes, presenting an opportunity for a small bowel or gastric full-thickness biopsy. Enteral tubes are sometimes used for decompression in highly symptomatic patients.27
For patients presenting with neurological symptoms, findings and serologic abnormalities have led to interest in immunotherapies. One is intravenous immunoglobulin, given parenterally. Several open-label studies have been published, the most recent one with 47 patients showing better response if glutamic acid decarboxylase–65 antibodies were present and with longer therapeutic dosing.28 Drawbacks to immunotherapies like intravenous immunoglobulin are cost and requiring parenteral access.
Other evaluation/treatments for drug refractory patients can be detailed as follows: First, an overall quality of life assessment can be helpful, especially one that includes impact of GpS on the patients and family. Nutritional considerations, which may not have been fully assessed, can be examined in more detail. Frailty assessments may show the need for physical therapy. Assessment for home care needs may indicate, in severe patients, needs for IV fluids at home, either enteral or parenteral, if nutrition is not adequate. Psychosocial and/or psychiatric assessments may lead to the need for medications, psychotherapy, and/or support groups. Lastly, an assessment of overall health status may lead to approaches for minimizing visits to emergency rooms and hospitalizations.29,30