Gastroparesis:  
Clinical Evaluation of 
Drugs for Treatment 
Guidance for Industry 
 
 
 
DRAFT GUIDANCE
 
 
  This guidance document is being distributed for comment purposes only. 
 
Comments and suggestions regarding this draft document should be submitted within 60 days of 
publication in the Federal Register of the notice announcing the availability of the draft 
guidance.  Submit electronic comments to https://www.regulations.gov.  Submit written 
comments to the Dockets Management Staff (HFA-305), Food and Drug Administration, 5630 
Fishers Lane, Rm. 1061, Rockville, MD  20852.  All comments should be identified with the 
docket number listed in the notice of availability that publishes in the Federal Register. 
 
For questions regarding this draft document, contact Maureen Dewey at 301-796-0845. 
 
 
 
 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
 
August 2019 
Clinical/Medical 
Revision 1 
6/21/2019   
Gastroparesis:  
Clinical Evaluation of 
Drugs for Treatment 
Guidance for Industry 
 
Additional copies are available from: 
 
Office of Communications, Division of Drug Information 
Center for Drug Evaluation and Research 
Food and Drug Administration 
10001 New Hampshire Ave., Hillandale Bldg., 4th Floor  
Silver Spring, MD  20993-0002  
Phone: 855-543-3784 or 301-796-3400; Fax: 301-431-6353; Email: druginfo@fda.hhs.gov 
https://www.fda.gov/drugs/guidance-compliance-regulatory-information/guidances-drugs 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
 
August 2019 
Clinical/Medical 
Revision 1 
   
TABLE OF CONTENTS 
 
I.  INTRODUCTION............................................................................................................. 1 
II.  BACKGROUND ............................................................................................................... 2 
III.  ENDPOINTS AND TRIAL DESIGN FOR GASTROPARESIS CLINICAL 
TRIALS .............................................................................................................................. 3 
A.  Trial Design .................................................................................................................................... 3 
B.  Trial Populations ............................................................................................................................ 4 
C.  Approach for Outcome Assessment Measures ............................................................................ 5 
D.  Trial Endpoints .............................................................................................................................. 6 
1. Primary Endpoints ........................................................................................................................... 6 
2. Secondary/Other Endpoints ............................................................................................................. 6 
3. Defining Clinically Meaningful Within-Patient Changes in Sign and Symptom Scores .................. 6 
E.  Statistical Considerations .............................................................................................................. 7 
REFERENCES .............................................................................................................................. 9 
  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
1  Gastroparesis:   
2  Clinical Evaluation of Drugs for Treatment 
3  Guidance for Industry1 
4   
5   
6   
7   
8  This draft guidance, when finalized, will represent the current thinking of the Food and Drug 
9  Administration (FDA or Agency) on this topic.  It does not establish any rights for any person and is not 
10  binding on FDA or the public.  You can use an alternative approach if it satisfies the requirements of the 
11  applicable statutes and regulations.  To discuss an alternative approach, contact the FDA staff responsible 
12  for this guidance as listed on the title page. 
13   
14   
15   
16   
17  I.  INTRODUCTION 
18   
19  The purpose of this guidance is to assist sponsors in the clinical development of drugs for 
20  treating idiopathic and diabetic gastroparesis.2  Specifically, this guidance addresses FDAs 
21  current recommendations regarding clinical trial designs and clinical endpoint assessments to 
22  support developing gastroparesis drugs. 
23   
24  This draft guidance is intended to serve as a focus for continued discussions among the 
25  responsible FDA divisions in the Office of New Drugs, pharmaceutical sponsors, the academic 
26  community, and the public.3 
27   
28  This guidance revises the draft guidance for industry of the same name issued in July 2015.  
29  Changes from the previous draft reflect FDAs current thinking about developing clinical 
30  outcome assessment tools and statistical considerations for using those tools to assess primary 
31  and secondary efficacy endpoints. 
32   
33  This guidance does not address detailed patient-reported outcome (PRO) instrument 
34  development and validation; these topics are addressed in the guidance for industry Patient-
                                                 
1 This guidance has been prepared by the Division of Gastroenterology and Inborn Errors Products in the Center for 
Drug Evaluation and Research at the Food and Drug Administration. 
 
2 For the purposes of this guidance, all references to drugs include both human drugs and therapeutic biological 
products unless otherwise specified. 
 
3 In addition to consulting guidances, sponsors are encouraged to contact the division to discuss specific issues that 
arise during the development of drugs to treat gastroparesis. 
 
 
1  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
35  Reported Outcome Measures:  Use in Medical Product Development to Support Labeling Claims 
36  (December 2009).4 
37   
38  More details regarding statistical analysis and clinical trial design are addressed in the ICH 
39  guidances for industry E9 Statistical Principles for Clinical Trials (September 1998) and E10 
40  Choice of Control Group and Related Issues in Clinical Trials (May 2001), respectively. 
41   
42  In general, FDAs guidance documents do not establish legally enforceable responsibilities.  
43  Instead, guidances describe the Agencys current thinking on a topic and should be viewed only 
44  as recommendations, unless specific regulatory or statutory requirements are cited.  The use of 
45  the word should in Agency guidances means that something is suggested or recommended, but 
46  not required. 
47   
48   
49  II.  BACKGROUND 
50   
51  Gastroparesis is a disorder characterized by delayed gastric emptying (DGE) in the absence of 
52  mechanical obstruction.  Symptoms are chronic with episodic exacerbation (Parkman et al. 
53  2004).  The idiopathic form of the disorder, which accounts for the greatest number of cases 
54  (Karamanolis et al. 2007), predominantly affects young adult females.  Gastroparesis is also 
55  frequently associated with diabetes (diabetic gastroparesis), which likely occurs because of 
56  impaired neural control of gastric motility (Parkman et al. 2004).  In addition, acute 
57  hyperglycemia has the potential to slow gastric emptying and decrease the effects of prokinetic 
58  drugs (Camilleri 2010). 
59   
60  The core signs and symptoms of gastroparesis are nausea (92 to 96 percent), vomiting (68 to 88 
61  percent), postprandial fullness (54 to 77 percent), early satiety (42 to 86 percent), and upper 
62  abdominal pain (36 to 85 percent) (Hoogerwerf et al. 1999; Anaparthy et al. 2009).  Patients may 
63  experience any combination of signs and symptoms with varying degrees of severity.  Pain is 
64  more prevalent in patients with idiopathic gastroparesis than it is in patients with diabetic 
65  gastroparesis.  Patients with diabetic gastroparesis may experience further derangement of 
66  glucose control because of unpredictable gastric emptying and altered absorption of orally 
67  administered hypoglycemic drugs. 
68   
69  Because the signs and symptoms of gastroparesis overlap with other gastrointestinal conditions, 
70  gastroparesis may be incorrectly diagnosed as bowel obstruction, functional dyspepsia, irritable 
71  bowel syndrome, or peptic ulcer disease.  In a patient with signs and symptoms suggestive of 
72  gastroparesis, a finding of DGE in the absence of an obstruction or alternative diagnosis provides 
73  critical support for the diagnosis of gastroparesis and can be assessed using either gastric 
74  emptying scintigraphy, the gastric emptying breath test, or the SmartPill motility testing system. 
75   
76  There is an urgent medical need for development of safe and effective therapies to treat patients 
77  with gastroparesis. 
78   
                                                 
4 We update guidances periodically.  To make sure you have the most recent version of a guidance, check the FDA 
guidance web page at https://www.fda.gov/regulatory-information/search-fda-guidance-documents. 
2  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
79  III.  ENDPOINTS AND TRIAL DESIGN FOR GASTROPARESIS CLINICAL 
80  TRIALS 
81   
82  Primary efficacy assessments for adequate and well controlled trials must be well defined and 
83  reliable.5  Because gastroparesis is a symptomatic condition, a well-defined and reliable PRO 
84  instrument that measures all the clinically important signs and symptoms of gastroparesis would 
85  be the ideal primary efficacy-assessment tool in clinical trials used to support labeling claims for 
86  treating gastroparesis.6  However, we are currently not aware of such a measure.  Until an 
87  appropriate PRO instrument for gastroparesis becomes available, sponsors should consider the 
88  strategies discussed in the following sections when designing gastroparesis clinical trials.  
89  Sponsors may also wish to review FDAs Center for Drug Evaluation and Research Clinical 
90  Outcome Assessment (COA) Drug Development Tool Qualification Program web page for 
91  information on qualified tools or tools currently under development. 
92   
93  Sponsors may wish to include and evaluate well-defined PRO instruments assessing the relevant 
94  and important signs and symptoms in early drug development  and evaluate the results in 
95  dose-ranging phase 2 trials or stand-alone noninterventional studies  to support their future use 
96  in phase 3 trials.  We encourage early and regular discussions with FDA regarding the 
97  development of these PRO instruments. 
98   
99  Because gastroparesis manifests as more than one core sign or symptom, the effect of new drugs 
100  intended to treat gastroparesis on each core sign and symptom should be assessed.  Early phase 
101  trials should help inform which of the core signs and/or symptoms should be included as 
102  prespecified endpoints intended to support labeling claims, based on which signs or symptoms 
103  the treatment is likely to improve.  It is important to show that even drugs intended to treat only a 
104  subset of the core signs or symptoms, based on the mechanism of the drug, do not worsen the 
105  remaining signs or symptoms of gastroparesis.  For example, a drug may be expected to improve 
106  gastroparesis-related nausea and vomiting but not abdominal pain based on its mechanism of 
107  action.  In this scenario, clinical studies should demonstrate that nausea and vomiting improved 
108  and that the treatment did not worsen the symptoms of abdominal pain, postprandial fullness, and 
109  early satiety. 
110   
111  The following sections provide recommendations regarding trial design, trial populations, 
112  outcome assessment measures, trial endpoints, and statistical considerations. 
113   
114  A.  Trial Design 
115   
116  In general, the trial design should consist of a randomized, double-blind, placebo-controlled trial 
117  and should include a 1- to 2-week screening period.  The screening period can be used for 
118  investigators to establish the presence and persistence of trial-entry criteria and for patients to 
119  gain experience completing the PRO instruments employed in the trial and demonstrate adequate 
                                                 
5 21 CFR 314.126. 
 
6 See the guidance for industry Patient-Reported Outcome Measures:  Use in Medical Product Development to 
Support Labeling Claims. 
 
3  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
120  understanding of and compliance with completing these instruments.  The screening period 
121  assessments of gastroparesis signs and symptoms can serve as the baseline values used in the 
122  analyses of the primary endpoint (see section III. D., Trial Endpoints).  FDA recommends a 
123  baseline assessment period of at least 7 days.  The primary endpoint should measure the change 
124  in signs and symptoms from baseline over a treatment period of at least 12 weeks duration. 
125   
126  Trial designs should address the need for maintenance treatment to prevent recurrence of signs or 
127  symptoms. 
128   
129  Endpoint assessment should be based on patients daily reporting to avoid recall error, and the 
130  protocol should state whether rescue medication (i.e., protocol-specified therapy for continued 
131  exacerbation of symptoms that is standardized across study sites) is allowed.  Daily diaries 
132  should be collected throughout the entire trial. 
133   
134  In addition, we recommend a randomized, controlled, long-term safety study of 12 months 
135  duration, with appropriate prespecified provisions for rescue medications, which should be 
136  conducted before submitting a new drug application. 
137   
138  B.  Trial Populations 
139   
140  Idiopathic and diabetic gastroparesis patients should be studied in separate clinical trials.  In 
141  general, diabetic gastroparesis patients experience the same core signs and symptoms as patients 
142  with idiopathic gastroparesis, but individual signs and symptoms may occur more often or with 
143  greater severity in one population compared with the other, and the degree of diabetic control can 
144  also confound results.  To fully describe safety and efficacy in each population, we recommend 
145  separate trials.  Because idiopathic and diabetic gastroparesis are closely related conditions, a 
146  single phase 3 trial in each population with demonstration of reliable and clinically meaningful 
147  results may support approval for both indications.7 
148   
149  We recommend that trial-entry criteria include the following: 
150   
151    The trial populations should have a clinical diagnosis of idiopathic or diabetic 
152  gastroparesis (for the individual trials) based on a documented history of gastroparesis 
153  symptoms, exclusion of other potential etiologies, and DGE (Abell et al. 2008; 
154  Parkman et al. 2004).  To optimize the ability to demonstrate a treatment effect, the 
155  trial should enroll patients with higher symptom severity (moderate to severe).  
156  Because there are currently no accepted definitions of gastroparesis severity, the 
157  sponsor should provide a justification for the severity index selected, including what 
158  defines moderate and severe symptoms. 
159   
160    Diabetic gastroparesis patients should have controlled and stable blood glucose levels.  
161  Patients prone to acute hyperglycemic events may confound interpretation of the 
162  therapeutic effect of the drug. 
163   
                                                 
7 See the guidance for industry Providing Clinical Evidence of Effectiveness for Human Drug and Biological 
Products (May 1998). 
4  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
164    Patients on opioids should be excluded because opioid use may affect gastrointestinal 
165  motility and potentially confound results. 
166   
167  C.  Approach for Outcome Assessment Measures 
168   
169  Until a well-defined and reliable PRO instrument that measures all the clinically important signs 
170  and symptoms of gastroparesis is available, we recommend that the five core signs and 
171  symptoms of gastroparesis  nausea, vomiting, postprandial fullness, early satiety, and 
172  abdominal pain  be included as endpoints in well-controlled clinical trials (Karamanolis et al. 
173  2007; Hoogerwerf et al. 1999; Anaparthy et al. 2009).  Sponsors should identify and empirically 
174  justify the questionnaire items (and their wording) used to assess signs or symptoms of 
175  gastroparesis that will be included in the trial.8 
176   
177  Each sponsor should propose a primary endpoint definition (see section III. D. Trial Endpoints) 
178  and a method for measuring each of the five signs and symptoms as described below.  Piloting 
179  the proposed instrument(s) in phase 2 trials can provide an opportunity to evaluate the ability of 
180  the instrument(s) to detect change, provide guidelines for interpretation of clinically meaningful 
181  within-patient change, and confirm the endpoint definition.  Pilot results can further inform plans 
182  for implementation of the proposed instrument(s) in the phase 3 trials.  Wording of the 
183  questionnaire should be carefully thought out so the questions or requests do not overlap in their 
184  measurement concepts (e.g., postprandial fullness and early satiety), and the concepts should be 
185  well-defined so that they are interpreted in a consistent way by patients (i.e., the questionnaire 
186  should include definitions for postprandial fullness, early satiety, or other terms that may vary in 
187  their interpretation among patients).  Each core sign and symptom should be separately measured 
188  and documented in the clinical trial. 
189   
190  The sponsor should also specify the mode of data collection that will be used by patients to 
191  record their daily signs and symptoms (e.g., electronic diary). 
192   
193  All signs and symptoms except vomiting should be rated by severity.  For example, question or 
194  request item responses can range from 0 for no symptom to 4 for the most severe symptom 
195  (0=none; 1=mild; 2=moderate; 3=severe; and 4=very severe) or have a numerical rating scale 
196  from 0 to 10, where 0 reflects the absence of the symptom and 10 reflects the worst possible 
197  symptom experience.  When possible, the rating scale should be consistent across the core signs 
198  and symptoms.  We recommend that reporting of vomiting in a daily symptom diary be 
199  measured by frequency rather than severity.  Frequency should be reported as the exact number 
200  of times over a 24-hour period, and a clear definition of what is considered one time of 
201  vomiting should be provided to patients to ensure consistency both within and between patients 
202  in reporting the number of times vomiting has occurred.  The severity of nausea, postprandial 
203  fullness, early satiety, and abdominal pain should be recorded based on the patients worst 
204  experience over a 24-hour period. 
205   
                                                 
8 See the guidance for industry Patient-Reported Outcome Measures:  Use in Medical Product Development to 
Support Labeling Claims. 
5  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
206  D.  Trial Endpoints 
207   
208  1.  Primary Endpoints 
209   
210  Changes in patient-reported signs and symptom scores should form the basis of the primary 
211  efficacy assessment in therapeutic trials for idiopathic and diabetic gastroparesis.  The primary 
212  endpoint should be based on patients core signs and symptoms or a subset of them.  Gastric 
213  emptying time should not be used as a primary efficacy endpoint because changes in gastric 
214  emptying time are not associated with the changes in the clinically important signs and 
215  symptoms in patients with gastroparesis. 
216   
217  The primary endpoint should measure change in signs and symptoms from baseline.  The 
218  analysis plan should include an evaluation of treatment effect throughout the 12-week study 
219  period. 
220   
221  We recommend the use of an endpoint that is based on core signs and symptoms.  This may be 
222  based on prespecified core signs and symptoms or a symptom severity summary score 
223  (excluding vomiting) and vomiting frequency (collected as a continuous variable).  The primary 
224  endpoint should not be limited to a single sign or symptom.  If sponsors propose a summary 
225  score, they should evaluate question-level (or request-level) responses to determine whether 
226  individual questions (or requests) overly influence the total score.  Currently, we do not have 
227  evidence to recommend one approach over the other.  Scores based on severity should be 
228  analyzed separately from those based on frequency (e.g., vomiting). 
229   
230  2.  Secondary/Other Endpoints 
231   
232  FDA recommends that changes from baseline in the individual signs and symptoms that are not 
233  assessed as part of the primary endpoint be measured as secondary endpoints.  Therefore, the 
234  primary and secondary endpoints should include an evaluation of all five core signs and 
235  symptoms.  Change in gastric emptying time can be measured as a secondary endpoint if desired 
236  (Abell et al. 2008).  The prespecified plan should address an analysis of the remaining core signs 
237  or symptoms that are not included in the primary endpoint. 
238   
239  3.  Defining Clinically Meaningful Within-Patient Changes in Sign and Symptom 
240  Scores 
241   
242  To aid in the interpretation of the results, sponsors should determine the amount of change that is 
243  meaningful to patients, in a total summary score or in individual sign and symptom scores.  
244  Ideally, this should be based on actual data and established in advance of phase 3 trials, so 
245  clinically meaningful within-patient change thresholds may be prespecified.  There are two 
246  clinically meaningful change thresholds of interest:  one for a clinically important improvement 
247  from baseline and one for a clinically important deterioration from baseline.  Depending on the 
248  proposed mechanism of action of the drug and trial objectives, a proposed threshold can specify 
249  some level of improvement in each of the five core signs and symptoms, or it can specify some 
250  level of improvement in a subset of those core signs and symptoms.  Worsening of core signs 
6  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
251  and symptoms would be inconsistent with the expected clinical benefit and taken into account 
252  when evaluating benefit and risk. 
253   
254  We recommend the use of an anchor-based approach, typically using phase 2 trial data, to 
255  estimate clinically meaningful change.  For this approach, we recommend including in phase 2 
256  and 3 trials multiple anchor scales, such as patient global impression of severity (PGIS) and 
257  patient global impression of change (PGIC) scales, with the intent of providing accumulated 
258  evidence to help interpret a clinically meaningful within-patient score change.  In contrast to a 
259  PGIC scale, a PGIS scale is not subject to recall error and can also be used to assess change from 
260  baseline data.  The PGIS scale is the preferred anchor scale over the PGIC scale; however, there 
261  is no perfect anchor scale, and it is helpful to include multiple anchor scales for anchor-based 
262  analyses. 
263   
264  The following item, which could be asked of patients (following the assessment schedule and 
265  recall period of the prespecified endpoint) and at baseline, is an example of a PGIS scale: 
266   
267  Please choose the response below that best describes the severity of your gastroparesis 
268  symptoms over the [insert appropriate recall period here]. 
269   
270  Sponsors can consider the following response options to this item:  0=none; 1=mild; 
271  2=moderate; 3=severe; and 4=very severe. 
272   
273  The following item, which could be asked weekly of patients, is an example of a PGIC scale: 
274   
275  Please choose the response below that best describes the overall change in your 
276  gastroparesis symptoms since you started taking the study medication. 
277   
278  Sponsors can consider the following response options to this item:  much better, a little better, no 
279  change, a little worse, much worse. 
280   
281  Sponsors should determine the clinically meaningful within-patient change threshold range using 
282  anchor-based methods (e.g., patient global impression scale as an anchor), supplemented with 
283  empirical cumulative distribution functions (eCDFs) of within-patient score change.  Separate 
284  eCDF curves should be generated for each meaningful anchor category (e.g., improved, no 
285  change, worsened) using data pooled across trial arms. 
286   
287  E.  Statistical Considerations 
288   
289  To evaluate daily diary assessments created during a trial, an adequate number of the 
290  assessments should be available.  The sponsor can determine this number based on evidence 
291  derived from the particular PRO assessment used in the trial.  For example, if a weekly summary 
292  score is used, in general, the sponsor should provide assessments from at least 4 of the 7 days.  
293  However, evidence from a particular PRO assessment may support the need for data from a 
294  higher number of days for that instrument to provide reliable results. 
295   
7  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
296  The efficacy analysis plan should clearly define how patients who take rescue medication will be 
297  considered in the final analysis.  Sponsors also should propose methods for handling missing 
298  data, including missing rescue medication data and missing PRO data at both question or request 
299  and instrument levels, in the analysis plan.  Sponsors should consider different approaches before 
300  the trial is initiated and the properties of these approaches should be evaluated. 
301   
302  We recommend that sponsors analyze the primary and secondary endpoints as continuous or 
303  ordinal variables; we do not recommend the use of percentage change.  In general, a traditional 
304  responder analysis would not be appropriate unless the targeted response is complete resolution 
305  of signs and symptoms.  In addition, we encourage the use of baseline values and other 
306  covariates to improve the efficiency of primary and secondary endpoint analyses. 
307   
308  Additionally, sponsors should submit supportive descriptive analyses (i.e., graphs of eCDFs of 
309  within-patient change from baseline for primary and secondary endpoints by treatment arm) for 
310  FDA review. 
8  Contains Nonbinding Recommendations 
Draft  Not for Implementation 
311  REFERENCES 
312   
313  Abell TL, RK Bernstein, T Cutts, G Farrugia, J Forster, WL Hasler, RW McCallum, KW Olden, 
314  HP Parkman, CR Parrish, PJ Pasricha, CM Prather, EE Soffer, R Twillman, and AI Vinik, 2006, 
315  Treatment of Gastroparesis:  A Multidisciplinary Clinical Review, Neurogastroenterol Motil 
316  18:263283. 
317   
318  Abell TL, M Camilleri, K Donohoe, WL Hasler, HC Lin, AH Nauer, RW McCallum, T Nowak, 
319  ML Nusynowitz, HP Parkman, P Shreve, LA Szarka, WJ Snape, and HA Ziessman, 2008, 
320  Consensus Recommendations for Gastric Emptying Scintigraphy:  A Joint Report of the 
321  American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine, Am 
322  J Gastroenterol, 103:753763. 
323   
324  Anaparthy R, N Pehlivanov, J Grady, H Yimei, and PJ Pasricha, 2009, Gastroparesis and 
325  Gastroparesis-Like Syndrome:  Response to Therapy and Its Predictors, Dig Dis Sci, 
326  54(5):10031010. 
327   
328  Hoogerwerf WA, PJ Pasricha, AN Kalloo, and MM Schuster, 1999, Pain:  The Overlooked 
329  Symptom in Gastroparesis, Am J Gastroenterol, 94:10291033. 
330   
331  Karamanolis G, P Caenepeel, J Arts, and J Tack, 2007, Determinants of Symptom Pattern in 
332  Idiopathic Severely Delayed Gastric Emptying:  Gastric Emptying Rate or Proximal Stomach 
333  Dysfunction? Gut, 56:2936. 
334   
335  Parkman HP, WL Hasler, and RS Fisher, 2004, American Gastroenterological Association 
336  Technical Review on the Diagnosis and Treatment of Gastroparesis, Gastroenterology, 
337  127(5):15921622. 
338   
339  Parkman HP, K Yates, WL Hasler, L Nguyen, PJ Pasricha, WJ Snape, G Farrugia, KL Koch, J 
340  Calles, TL Abell, RW McCallum, L Lee, A Unalp-Arida, J Tonascia, and F Hamilton, 2011, 
341  Similarities and Differences Between Diabetic and Idiopathic Gastroparesis, Clin Gastroenterol 
342  Hepatol, 9:10561064. 
  9