Effect of somatostatin on diarrhea and on small intestinal water and electrolyte transport in a patient with pancreatic cholera

Contemporary Approaches to the Surgical Management of Pancreatic Neuroendocrine Tumors

The incidence of pancreatic neuroendocrine tumors (PNETs) is on the rise primarily due to the increasing use of cross-sectional imaging. Most of these incidentally detected lesions are non-functional PNETs with a small proportion of lesions being hormone-secreting, functional neoplasms. With recent advances in surgical approaches and systemic therapies, the management of PNETs have undergone a paradigm shift towards a more individualized approach. In this manuscript, we review the histologic classification and diagnostic approaches to both functional and non-functional PNETs. Additionally, we detail multidisciplinary approaches and surgical considerations tailored to the tumor's biology, location, and functionality based on recent evidence. We also discuss the complexities of metastatic disease, exploring liver-directed therapies and the evolving landscape of minimally invasive surgical techniques.

Treatment options of metastatic and nonmetastatic VIPoma: a review

PURPOSE

VIPoma belongs to the group of neuroendocrine neoplasms. These tumours are located mostly in the pancreas and produce high levels of vasoactive intestinal peptide (VIP). In most cases, a metastatic state has already been reached at the initial diagnosis, with high levels of VIP leading to a wide spectrum of presenting symptoms. These symptoms include intense diarrhoea and subsequent hypopotassaemia but also cardiac complications, with life-threatening consequences. Treatment options include symptomatic therapy, systemic chemotherapy and targeted therapy, as well as radiation and surgery. Due to the low incidence of VIPoma, there are no prospective studies or evidence-based therapeutic standards to date.

METHODS

To evaluate the possible impact of different therapy strategies, we performed literature research using PubMed.

RESULTS

All possible treatment modalities for VIPoma have at least one of two therapy goals: antisecretory effects (symptom control) and antitumoural effects (tumour burden reduction). Symptomatic therapy is the most important in the emergency setting to rehydrate, balance electrolytes and stabilise the patient. Symptomatic therapy is also of great importance perioperatively. Somatostatin analogues play a major role in symptom control, although their efficiency is often limited. Chemotherapy may be effective in reaching stable disease for a certain time period, although its impact on symptom control is limited and often delayed. Among targeted therapy options, the usage of sunitinib appears to be the most effective in terms of symptom control and showing antitumoural effects at the same time. Experience with radiation is still limited; however, local ablative procedures seem to be promising options. Peptide receptor radiotherapy (PRRT) with radiolabelled somatostatin analogues (SSAs, 177Lu-DOTATATE) offers a targeted approach, especially in patients with high somatostatin receptor density. Surgery is the first-line therapy for nonmetastatic VIPoma. Additionally, if the resection of all visible tumour lesions is possible, the surgical approach seems preferable to other strategies in highly symptomatic patients. The role of surgery in very advanced stages where only tumour debulking is possible remains debatable. However, a high rate of immediate symptom control can be achieved by tumour debulking followed by somatostatin therapy, although the impact on survival remains unclear.

CONCLUSION

Surgery is the only curative option for nonmetastatic VIPoma. Additionally, surgery should be a first-line therapy option for highly symptomatic patients, especially if the resection of all tumour lesions (primary tumour and metastasis) is achievable. In frail patients, other modalities can be used.

Efficacy of treatments for VIPoma: A GTE multicentric series

BACKGROUND

Vasoactive intestinal peptide-secreting tumor (VIPoma) is a very rare, life-threatening, functioning pancreatic neuroendocrine tumor (pNET). The efficacy of antitumor therapies against functioning symptoms and tumor burden have been poorly described in VIPoma.

OBJECTIVE

Describe the impact of treatments on the secretory syndrome, tumor burden and survival in patients with VIPoma.

METHODS

We retrospectively reviewed the records of patients with VIPoma treated in seven French expert centers between 1990 and 2016. Diagnostic of VIPoma was reassessed using strict criteria. We evaluated the antisecretory efficacy (>50 % decrease of daily bowel movements), and antitumor efficacy (RECIST 1.1) of all treatments received.

RESULTS

Twenty-two patients were included. pNETs were mostly metastatic (77 %) and classified as grade 2 (83 %). Median follow-up was 78.2 months. Surgical excision of nonmetastatic VIPoma effectively controlled the secretory syndrome. Although 4/5 patients had metastatic recurrences, all patients were alive after median post-operative follow-up of 171 months. Among the 87 treatments received for metastatic VIPoma, curative-intent surgery (n = 14), somatostatin analogs alone (n = 11), chemotherapy (n = 23), transarterial liver embolization (TALE) (n = 14), everolimus (n = 10) and sunitinib (n = 7) achieved, respectively, 100 %, 67 %, 83 %, 50 %, 20 % and 100 % antisecretory efficacy. The 5-year OS rate was 63.6 %, with pejorative impact of higher Ki-67 index (P = 0.045) and higher plasma VIP concentration (P = 0.025).

CONCLUSIONS

Surgical resection of localized VIPoma is effective but rarely curative. For metastatic VIPoma, curative-intent surgery, chemotherapy and sunitinib are the therapeutic options that best combined antitumor and antisecretory efficacies.

Is Lanreotide Really Useful in High Output Stoma? Comparison between Lanreotide to Conventional Antidiarrheal Treatment Alone

BACKGROUND

The incidence of high-output stoma (HOS) was reported to be approximately 3 to 16% in the literature, and HOS can cause dehydration. This complication is often severe enough to warrant hospital readmission and may result in renal failure. The aim of this study was to show a decrease of 50% in ileostomy output in the experimental arm using lanreotide treatment.

METHODS

Patients with an ileostomy output ≥ 1.5 l/24 hours were included in this prospective, open, multicentre randomized trial. Patients were randomly allocated between treatment arms with either lanreotide (LAN) and antidiarrhoeal treatments (TAD) (LAN-TAD group) or antidiarrhoeal treatments only (TADS group). The primary outcome was ileostomy output after 72 days. The secondary endpoints were ileostomy output during the first 6 days, blood urea and creatinine values, hospital length of stay and serious adverse events.

RESULTS

In the per-protocol analysis, there were nine patients in the control group (TADS) and six patients in the experimental group (TAD-LAN group). The stoma outputs at Day 3 (D3) in the experimental and control groups were 1,900 ± 855.7 mL and 1,728.6 ± 845.5 mL, respectively (p = 0.2). No differences were found concerning stoma output at D6, renal function, or hospital length of stay between the two groups.

CONCLUSION

The trial was prematurely stopped due to the low number of patients included. The question of the usefulness of somatostatin analogues in HOS persists, especially as the cost of this treatment is high, and there is a lack of evidence of its effectiveness.

Changes in Somatostatin-Like Immunoreactivity in the Sympathetic Neurons Projecting to the Prepyloric Area of the Porcine Stomach Induced by Selected Pathological Conditions

The aim of the present study was to define changes in the expression of somatostatin (SOM) in the sympathetic perikarya innervating the porcine stomach prepyloric area during acetylsalicylic-acid-induced gastritis (ASA) and experimentally induced hyperacidity (HCL) and following partial stomach resection (RES). On day 1, the stomachs were injected with neuronal retrograde tracer Fast Blue (FB). Animals in the ASA group were given acetylsalicylic acid orally for 21 days. On the 22nd day after FB injection, partial stomach resection was performed in RES animals. On day 23, HCL animals were intragastrically given 5 ml/kg of body weight of a 0.25 M aqueous solution of hydrochloric acid. On day 28, all pigs were euthanized. Then, 14-μm thick cryostat sections of the coeliac-superior mesenteric ganglion (CSMG) complexes were processed for routine double-labelling immunofluorescence. All pathological conditions studied resulted in upregulation of SOM-like (SOM-LI) immunoreactivity (from 14.97 ± 1.57% in control group to 33.72 ± 4.39% in the ASA group, to 39.02 ± 3.65% in the RES group, and to 29.63 ± 0.85% in the HCL group). The present studies showed that altered expression of SOM occurs in sympathetic neurons supplying the prepyloric area of the porcine stomach during adaptation to various pathological insults.

Irinotecan- and 5-fluorouracil-induced intestinal mucositis: insights into pathogenesis and therapeutic perspectives

PURPOSE

Intestinal mucositis and diarrhea are common manifestations of anticancer regimens that include irinotecan, 5-fluorouracil (5-FU), and other cytotoxic drugs. These side effects negatively impact therapeutic outcomes and delay subsequent cycles of chemotherapy, resulting in dose reductions and treatment discontinuation. Here, we aimed to review the experimental evidence regarding possible new targets for the management of irinotecan- and 5-FU-related intestinal mucositis.

METHODS

A literature search was performed using the PubMed and MEDLINE databases. No publication time limit was set for article inclusion.

RESULTS

Here, we found that clinical management of intestinal mucositis and diarrhea is somewhat ineffective at reducing symptoms, possibly due to a lack of specific targets for modulation. We observed that IL-1β contributes to the apoptosis of enterocytes in mucositis induced by 5-FU. However, 5-FU-related mucositis is far less thoroughly investigated with regard to specific molecular targets when compared to irinotecan-related disease. Several studies have proposed that a correlation exists between the intestinal microbiota, the enterohepatic recirculation of active metabolites of irinotecan, and the establishment of mucositis. However, as reviewed here, this association seems to be controversial. In addition, the pathogenesis of irinotecan-induced mucositis appears to be orchestrated by interleukin-1/Toll-like receptor family members, leading to epithelial cell apoptosis.

CONCLUSIONS

IL-1β, IL-18, and IL-33 and the receptors IL-1R, IL-18R, ST2, and TLR-2 are potential therapeutic targets that can be modulated to minimize anticancer agent-associated toxicity, optimize cancer treatment dosing, and improve clinical outcomes. In this context, the pathogenesis of mucositis caused by other anticancer agents should be further investigated.

Role of octreotide in post chemotherapy and/or radiotherapy diarrhea: prophylaxis or therapy?

AIM

The clinical efficacy of octreotide in controlling chemoradiotherapy-induced diarrhea remains controversial. We conducted a meta-analysis of randomized controlled trials (RCT) comparing octreotide with placebo in the prevention or therapy of chemoradiotherapy-induced diarrhea.

METHODS

A computerized literature search of Medline, EMBASE, Cochrane Library and BIOSIS databases were performed for RCT comparing the use of octreotide versus placebo in the management of patients with chemoradiotherapy-induced diarrhea. The main outcome measure was the response of the diarrhea.

RESULTS

We included eight RCT comprising 572 patients. We found octreotide was significantly effective compared with the placebo (OR, 4.9; 95%, 1.58-15.2).The overall effect of octreotide was 69% (204/294), while that of placebo was 54% (149/278). When divided into prophylactic and therapeutic subgroups, the prophylactic subgroup had an OR of 2.11 (95% CI, 0.51-2.89) for chemoradiotherapy-induced diarrhea and the therapeutic subgroup had an OR of 7.30 (95% CI, 4.09-13.04).

CONCLUSION

In chemoradiotherapy-induced diarrhea, octreotide is best used as a therapeutic rather than a prophylactic agent against diarrhea.

Octreotide acetate in prevention of chemoradiation-induced diarrhea in anorectal cancer: randomized RTOG trial 0315

BACKGROUND

In anorectal cancer patients, an acute side effect of chemoradiotherapy is gastrointestinal toxicity, which often impedes treatment delivery. Based on previous trials, octreotide acetate is widely recommended for the control of chemotherapy-induced diarrhea. However, the effectiveness of octreotide in preventing or controlling radiation- and chemoradiation-induced diarrhea is not known.

METHODS

A randomized, double-blinded, placebo-controlled trial was designed to determine the efficacy of long-acting octreotide acetate (LAO) in preventing the onset of acute diarrhea in patients undergoing chemoradiation therapy for rectal or anal cancer. Between 4 and 7 days before the start of radiation therapy, patients received a 30-mg dose of LAO (109 patients) or placebo (106 patients) via intramuscular injection. A second dose was given on day 22 (+/-3 days) of radiation treatment. A total of 215 patients were included in the final analysis. The primary endpoint was the incidence of grade 2-4 acute diarrhea; secondary endpoints included treatment compliance, medical resource utilization, patient-reported bowel function, and quality of life (QoL). Statistical tests were one- or two-sided, as specified.

RESULTS

After a median follow-up time of 9.64 months, incidence rates of grades 2-4 acute diarrhea were similar in both groups (49% placebo vs 44% LAO; P = .21). No statistically significant treatment differences in chemotherapy or radiation delivery, medical resource utilization, patient-reported bowel function, or QoL were observed.

CONCLUSION

In this study, the prophylactic use of LAO did not prevent the incidence or reduce the severity of diarrhea and had no notable impact on patient-reported bowel function or QoL.

Changes in the somatostatin (SOM)-like immunoreactivity within nervous structures of the porcine descending colon under various pathological factors

This study reports on changes in the somatostatin-like immunoreactive (SOM-LI) nerve structures of the enteric nervous system (ENS) in the porcine descending colon, caused by chemically driven inflammation, proliferative enteropathy (PE), which is a "natural" inflammation with proliferative changes and nerve injury (axotomy). The distribution pattern of SOM-LI structures was studied using the immunofluorescence technique in the circular muscle layer, the myenteric (MP), outer submucous (OSP) and inner submucous plexuses (ISP) and also in the mucosal layer. Under physiological conditions SOM-LI perikarya have been shown to constitute 1.97+/-0.36%, 2.06+/-0.33% and 4.23+/-0.40% in the MP, OSP and ISP, respectively. Changes in SOM-immunoreactivity depended on the pathological factor and the part of the ENS studied. Numbers of the SOM-LI perikarya amounted 1.81+/-0.30, 1.97+/-0.24 and 11.15+/-0.95 during chemically induced colitis and 3.21+/-0.37%, 4.33+/-0.33% and 4.42+/-0.32% after axotomy in MP, OSP and ISP, respectively. Moreover during PE SOM-positive cell bodies were not observed at all in MP, whereas within OSP and ISP the number of SOM-LI perikarya amounted to 3.34+/-0.36 and 10.92+/-059, respectively. All processes studied resulted in a decrease in the number of SOM-LI nerve fibers in the mucosal layer, whereas within the circular muscle layer chemically induced inflammation and axotomy caused an increase in the number of the SOM-LI nerve fibers contrary to PE, which reduced the number of such fibers. The obtained results suggest that SOM-LI nerve structures of the ENS may participate in various pathological states within the porcine descending colon and their functions probably depend on the type of pathological factor.

Phase III, double-blind study of depot octreotide versus placebo in the prevention of acute diarrhea in patients receiving pelvic radiation therapy: results of North Central Cancer Treatment Group N00CA

PURPOSE

To assess the effectiveness of depot octreotide for the prevention of diarrhea during pelvic radiation therapy.

PATIENTS AND METHODS

Patients receiving pelvic radiation therapy (planned minimum dose, 45 Gy; 1.7 to 2.1 Gy daily) were eligible for the study. From May 10, 2002, through October 14, 2005, 125 patients were randomly allocated in a double-blind fashion to receive octreotide (100 microg, administered subcutaneously on day 1, followed by depot octreotide, 20 mg, administered intramuscularly on days 2 and 29; n = 62) or to receive a placebo (n = 63).

RESULTS

Grade 0, 1, 2, and 3 diarrhea were observed in 18%, 31%, 31%, and 21% of patients in the octreotide arm, respectively, and in 25%, 32%, 22%, and 21% of patients in the placebo arm, respectively (P = .64). Grade 0, 1, 2, and 3 abdominal cramps were observed in 32%, 45%, 21%, and 2% of patients receiving octreotide, respectively, and in 51%, 24%, 21%, and 5% of patients receiving the placebo, respectively (P = .053). Some patient-reported symptoms were worse in the octreotide group, including nocturnal bowel movements (70% v 45%; P = .004), clustering of bowel movements (90% v 69%; P = .004), and bleeding with bowel movements (57% v 35%; P = .01).

CONCLUSION

As administered in this study, octreotide did not decrease diarrhea during pelvic radiation therapy. Some gastrointestinal symptoms were worse in patients treated with octreotide. Octreotide is not indicated for prevention of diarrhea during pelvic radiation therapy.

Neuroendocrine tumors. Biotherapy

This review gives an introduction to the classification and staging of neuroendocrine tumors, as the prognostic implications of these classifications influence therapeutic decisions. The indications for biotherapy are given, together with a short update on the mechanism of somatostatin analogs and interferon-alpha therapy. This is followed by an in-depth description of the use of biotherapy, its results with respect to symptomatic and antiproliferative treatment, as well as its side-effects.

Vasoactive intestinal polypeptide-secreting tumours: biology and therapy

VIP-secreting tumours are rare, but they produce a dramatic clinical picture, the most prominent feature being profuse, watery diarrhoea and hypokalaemia. VIPomas are malignant and require sophisticated diagnostic and localization techniques in order to identify their presence. Delays in diagnosis are the rule rather than the exception. Improvements in the diagnosis of VIPomas appear to result in an increase in resectability rates. A definitive diagnosis is aided by the determination of plasma VIP concentrations through the use of sensitive radioimmunoassays. With heightened awareness of this syndrome, increasing numbers of patients can be identified and more effective treatments developed for the refractory and recurrent tumours.

Gastrointestinal endocrine tumours: medical management

With the introduction of longer-acting somatostatin analogues symptomatic relief is easy to achieve in patients with functionally active endocrine tumours and will be further facilitated by still longer-acting formulations. The consequences of gastric acid hypersecretion in patients with Zollinger-Ellison syndrome can be prevented by all proton-pump inhibitors currently on the market. Despite the various antiproliferative strategies that have been offered to patients with metastatic disease, available data are controversial and, more importantly, are supported by few prospective and controlled studies. Most experts agree that surgery with curative extirpation of the primary in the absence of metastases and tumour debulking in metastatic disease should be intended wherever possible. Controversy concerns residual disease. According to our view, any further antiproliferative strategy should consider the growth characteristics and biology of a given tumour (Figure 4). In the case of rapid progression, chemotherapy should be offered if tumours originate from the pancreas or reveal an undifferentiated histology. In contrast, chemotherapy should not be offered to patients with well-differentiated non-functional or functional tumours (carcinoid syndrome) arising from the intestine. The same applies for patients with tumours with no or only slow growth within an given observation period of 3-12 months. These patients should be treated only symptomatically. Patients with tumours of slow progression might favourably respond to long-acting somatostatin analogues. We start with octreotide and offer patients not responding to octreotide monotherapy additional IFN alpha. If further tumour progression takes place, hepatic artery embolization is the next step (Figure 5) followed by chemotherapy, the latter in patients with tumours of pancreatic origin only. This strategy recognizes the severity of side-effects of the different therapeutic modalities and starts with octreotide because of its very few side-effects. Other groups start with chemoembolization followed by octreotide, alpha-interferon or its combinations (Ahlman et al, 1996). Ongoing studies will, it is hoped, answer the question of the ideal sequence of therapeutic strategies. Every available patient with metastasised gastrointestinal endocrine tumours should be included in one of the ongoing European multicentre trials.

Efficacy of octreotide in diarrhoea due to Vibrio cholerae: a randomized, controlled trial

Although octreotide, a long-acting analogue of somatostatin, is currently used in the treatment of chronic secretory diarrhoea due to various causes, its role in the management of acute secretory diarrhoea is not well established. In the present study, therefore, the therapeutic value of octreotide in the management of cholera, a classical example of acute secretory diarrhoea, was investigated. During an outbreak of cholera, patients admitted with acute secretory diarrhoea of < or = 24 h duration and a purging rate > 100 ml/h were enrolled on the study and randomly assigned to octreotide (N = 17) and control (N = 16) groups. All 33 patients received intravenous fluid replacement and antibiotic treatment (200 mg ofloxacin twice daily for 3 days, by mouth). Each patient in the octreotide group was also given a subcutaneous injection containing 100 micrograms octreotide every 8 h for a maximum of six doses. The stool output of each patient was recorded every hour until there had been none for an hour, which was taken as the endpoint. Mean (S.D.) total stool output was lower [6.56 (3.7) v. 9.7 (6.5) litres] and the mean (S.D.) duration of diarrhoea after admission was shorter [32.9 (15.6) v. 47.8 (22.3); P < 0.05] in the octreotide group than in the control group. However, as both groups generally had similar purging rates, the higher volume of stools from the control group was simply the result of the longer period of diarrhoea in this group. Octreotide therefore only decreased the duration of diarrhoea in the cholera patients.

Lanreotide inhibits human jejunal secretion induced by prostaglandin E1 in healthy volunteers

1. Somatostatin inhibits hormonal secretions in the gastrointestinal tract. Somatostatin analogues are used in the treatment of VIPome-related watery diarrhoea. In addition, more than 10% of patients with AIDS suffer from diarrhoea likely due to the increased intestinal secretion of water and ions. However, the direct effect of somatostatin on the flux of water and ions in the intestine has not been, so far, analyzed in vivo. The aim of the present study was to evaluate the effect of lanreotide, a somatostatin analogue, on the movements of water and ions in the jejunum in man. 2. Accordingly, 10 healthy volunteers (age 18-35 years, mean 27) and two patients with AIDS (26 and 33 years) suffering from water diarrhoea (> 800 ml day-1) underwent intestinal perfusion using a four lumen tube with proximal occluding balloon. The segment tested was 25 cm long. The jejunum was infused by an isotonic control saline solution containing polyethylene glycol (PEG) as nonabsorbable marker. Basal jejunal secretions were measured in all subjects. Prostaglandin E1 (PGE1) was administered intraluminally to stimulate jejunal secretion in healthy volunteers. The effect of intravenous lanreotide on the jejunal PGE1-induced secretions of water and electrolytes was analysed in healthy subjects and on the basal secretions in AIDS patients. Each period was analyzed on the basis of three (10 min) successive intestinal juice collections after 20-30 min equilibration time. The antisecretory effect of lanreotide was evaluated in each subject as the difference between fluxes compared to the control period. 3. In healthy volunteers, PGE1 induced secretion of H2O, Na+, K+ and Cl- in the jejunum and lanreotide reduced significantly PGE1-induced response. In both AIDS patients basal fluxes of water and ions were reduced by lanreotide in a dose-dependent manner. 4. Somatostatin can reduce stimulated-jejunal secretion of ions and water in normal subjects and may improve water diarrhoea in AIDS patients.

Consensus statement: octreotide dose titration in secretory diarrhea. Diarrhea Management Consensus Development Panel

Octreotide is an effective therapeutic option in controlling secretory diarrhea of varied etiology. However, marked patient-to-patient differences in the antidiarrheal effects necessitate titration of octreotide dose in individual patients to achieve optimal symptom control. A consensus development panel established guidelines for octreotide dose titration in patients with secretory diarrhea. Overall, the panel recommended an aggressive approach in selecting the initial octreotide dose and in making subsequent dose escalations in patients with secretory diarrhea due to gastrointestinal tumors (eg, carcinoids, VIPomas), AIDS, dumping syndrome, short bowel syndrome, radiotherapy, or chemotherapy. To avoid hypoglycemia in patients with diabetes mellitus-associated secretory diarrhea, the panel recommended a low initial octreotide dose and a conservative titration regimen with close monitoring a blood glucose levels. The end point of therapy should focus on a reduction in diarrhea (frequency of bowel movements or stool volume) rather than normalization of hormonal profile. Overall, octreotide is well tolerated; principal side effects are transient injection site pain and gastrointestinal discomfort. For many patients with secretory diarrhea, octreotide therapy is expected to improve the overall health and quality of life and in the long run will lessen health care costs.

Pancreatic vipomas: spectrum of presentation and evolution of diagnostic and therapeutic modalities

Two patients are reported who presented with symptoms characteristic of a pancreatic vipoma. The necessity to measure more than one plasma VIP level for diagnosis, and the delay between the onset of illness and diagnosis is illustrated by both cases. Evidence suggests that vipomas are still under reported. The evolution of sophisticated diagnostic and therapeutic modalities over the twenty-five years separating both presentations is discussed.

Pathophysiology of potassium absorption and secretion by the human intestine

When normal people ingest 90 mEq/day of K+ in their diet, they absorb about 90% of intake (81 mEq) and excrete an equivalent amount of K+ in the urine. Normal fecal K+ excretion averages about 9 mEq/day. The vast majority of intestinal K+ absorption occurs in the small intestine; the contribution of the normal colon to net K+ absorption and secretion is trivial. K+ is absorbed or secreted mainly by passive mechanisms; the rectum and perhaps the sigmoid colon have the capacity to actively secrete K+, but the quantitative and physiological significance of this active secretion is uncertain. Hyperaldosteronism increases fecal K+ excretion by about 3 mEq/day in people with otherwise normal intestinal tracts. Cation exchange resin by mouth can increase fecal K+ excretion to 40 mEq/day. The absorptive mechanisms of K+ are not disturbed by diarrhea per se, but fecal K+ losses are increased in diarrheal diseases by unabsorbed anions (which obligate K+), by electrochemical gradients secondary to active chloride secretion, and probably by secondary hyperaldosteronism. In diarrhea, total body K+ can be reduced by two mechanisms: loss of muscle mass because of malnutrition and reduced net absorption of K+; only the latter causes hypokalemia. Balance studies in patients with diarrhea are exceedingly rare, but available data emphasize an important role for dietary K+ intake, renal K+ excretion, and fecal K+ losses in determining whether or not a patient develops hypokalemia. The paradoxical negative K+ balance induced by ureterosigmoid anastomosis is described. The concept that fecal K+ excretion is markedly elevated in patients with uremia as an intestinal adaptation to prevent hyperkalemia is analyzed; we conclude that the data do not convincingly show the existence of a major intestinal adaptive response to chronic renal failure.

Case report: defective beta and alpha cell regulation in patients with hyperinsulinemia and acanthosis nigricans

Beta cell hypersecretion is associated with the syndrome of hyperandrogenism, insulin resistance, and acanthosis nigricans. It is unknown whether concomitant alpha cell secretory dysfunction occurs in patients with this syndrome. The authors evaluated the gastroenteropancreatic hormones in four family members with varying degrees of the hyperandrogenism, insulin resistance, and acanthosis nigricans syndrome. Gastroenteropancreatic hormones were measured during oral glucose tolerance test with and without subcutaneous octreotide injection. The study revealed that the administration of subcutaneous octreotide resulted in suppression of beta cell function (insulin and c-peptide) but had no effect or a delayed effect on alpha cell secretion (glucagon). Furthermore, the severity of glucagon abnormalities paralleled that of beta cell hypersecretion and the clinical and phenotypic manifestations of acanthosis nigricans in our four patients. We speculate that this alpha cell aberration could potentially be involved in the altered glucose homeostasis and perhaps the skin manifestations of this syndrome. Therefore, glucagon levels should be evaluated in the hormonal studies in patients with hyperandrogenism, insulin resistance, and acanthosis nigricans syndrome.

Somatostatin analog sandostatin and inhibition of tumor growth in patients with metastatic endocrine gastroenteropancreatic tumors

A prospective study was performed to determine the efficacy of octreotide (Sandostatin; SMS 201-995) 200 micrograms tid in controlling tumor growth. The study included 21 patients with metastasized endocrine GEP tumors: 6 gastrinomas, 8 carcinoid syndromes, 7 nonfunctioning tumors. Treatment was performed for 3 to 59 months (median 15 months). Evaluation of the response to octreotide was facilitated in 12 patients by a pretreatment observation period of 3 to 47 months (median 17 months) during which the natural growth behavior was determined. Based on the presence or absence of a control period prior to treatment, 5 patients were considered to be responders, 7 as questionable responders (no pretreatment phase available), and 9 as nonresponders. None of the 21 patients had documented shrinkage of the tumor mass. The most favorable response was tumor standstill. In all but one responder an escape to an initially favorable response occurred after 6 to 28 months (median 14 months). Proved inhibition of growth was paralleled by a reduction of serum and urine hormone parameters, whereas unaltered progression of tumor growth was observed also in the presence of hormone suppression. Tumor growth and hormone release was inhibited in the absence and presence of somatostatin receptors on the tumor. It is concluded that octreotide exerts a limited effect on metastatic GEP tumor growth. The evaluation of a response to octreotide is facilitated by an observation period prior to the drug that provides information on growth characteristics of the tumor. The presence of octreotide receptors does not predict the success of therapy.

Use of octreotide acetate for control of symptoms in patients with islet cell tumors

Gut tumor syndromes are rare, occurring in less than two cases per million population per year: Insulinomas are most common and gastrinomas are less common; all the others are extremely rare. Conventional treatment of the symptoms caused by these tumors has included surgery, hepatic arterial embolization, and chemotherapy; some patients with Zollinger-Ellison syndrome (ZES) have been treated with specific agents such as gastric antisecretory drugs. The development of octreotide, a synthetic, long-acting analogue of the natural peptide somatostatin, has offered an alternative to such therapies. Octreotide has a half life of > 100 minutes and inhibits both physiological- and tumor release of many peptides. It also has direct effects on the gut that modify secretion and motility. Octreotide has been shown to be particularly useful for the symptoms of tumors producing vasoactive intestinal peptide (VIP), and of the carcinoid syndrome. It is also useful in patients with glucagonomas, with growth hormone-releasing hormone producing tumors, and in some patients with Cushing's syndrome and unresectable insulinomas. Octreotide is effective in patients with ZES, but alternative therapies such as omeprazole are more effective, safer, and more convenient for those patients. Side effects of octreotide have not been troublesome in these patients, but the incidence of long term effects is still not entirely clear. Octreotide has proved to be a significant advance in the treatment of patients with islet cell tumors.

In vivo inhibitory effect of lanreotide (BIM 23014), a new somatostatin analog, on prostaglandin- and cholera toxin-stimulated intestinal fluid in the rat

The antisecretory action of subcutaneously (SC) administered somatostatin(1-14), octreotide, and lanreotide on jejunal net flux of water under basal, prostaglandin E1 (PGE1)- and cholera toxin (CT)-stimulated secretory conditions was determined in vivo on isolated intestinal loop in anesthetized rats. Both PGE1 and CT induced intestinal hypersecretion in the rats. This secretory effect was not affected by SC administration of saline. Lanreotide (1, 10, and 100 micrograms/kg) reduced the maximal PGE1-induced secretion, while 200 micrograms/kg had no effect. Similarly, octreotide (1 and 10 micrograms/kg) and somatostatin (1-14) (0.1 and 1 microgram/kg) reduced the increase of net water flux induced by PGE1. However, higher doses of octreotide (100 and 200 micrograms/kg) and somatostatin(1-14) (10 and 100 micrograms/kg) had no effect on PGE1-induced secretion. Lanreotide, octreotide, and somatostatin(1-14) (1 and 10 micrograms/kg) abolished the maximal secretion induced by cholera toxin. However, 100 micrograms/kg of lanreotide, octreotide, and somatostatin(1-14) had no effect on cholera toxin-induced secretion. The present study shows that lanreotide, octreotide, and somatostatin(1-14) reduce the secretion induced by PGE1 and abolish that induced by CT. These effects were obtained with doses of less than 100 micrograms/kg of the products, higher doses being ineffective. The higher efficacy against CT-induced hypersecretion as compared to PGE1-induced hypersecretion suggests a direct antisecretory effect at the enterocyte level and indicates the usefulness of these products as antidiarrheal agents in nonhormonally mediated diarrhea.

Effects of sandostatin on neuroendocrine tumours of the gastrointestinal system

Sandostatin is a drug of immense importance in the management of NETs of the gastrointestinal tract. Its effect in some syndromes is life-saving, in particular in VIPoma. Dramatic effects have also been reported in the glucagonoma syndrome. The quality of life is considerably improved in the carcinoid syndrome and it is potentially life-saving in carcinoid crises. The drug is effective in gastrinomas, but other therapy is more effective. Its value is controversial in insulinoma although some patients are clearly improved. Not all patients respond and this may be related to the abundance of Sandostatin receptors on the tumour or simply to tumour bulk. There is no clear-cut evidence that Sandostatin has an anti-tumour effect in these patients.

Reduction of the effluent volume in high-output ileostomy patients by a somatostatin analogue, SMS 201-995

Twelve ileostomy patients were given subcutaneous SMS 201-995 therapy (100 micrograms t.d.s. for 5 days) in a randomized placebo-controlled trial. All patients had ileostomies constructed 60 cm proximal to the terminal ileum (proximal ileostomy) following restorative proctocolectomy. SMS 201-995 reduced the daily ileostomy output from 997 +/- 52 g to 736 +/- 28 g, P < 0.05, along with a decrease in daily sodium and chloride excretion (sodium: 92.60 +/- 8.51 to 75.22 +/- 8.64 mEq, chloride: 143.46 +/- 8.54 to 113.60 +/- 15.84 mEq; both P < 0.05). There were no significant changes in the plasma levels of glucagon, C peptide, insulin, renin or aldosterone with SMS 201-995 therapy. Patients developed no severe side effects and reported easier management of the ileostomy and a reduction in thirst. Our results suggest a possible clinical role for SMS 201-995 in the management of proximal ileostomy.

Secretory diarrhea in villous adenoma of rectum: effect of treatment with somatostatin and indomethacin

The effects of treatment with the synthetic long-acting somatostatin analogue SMS-201-995 were studied in a patient with a fluid and electrolyte secreting villous adenoma of the rectum. The effects of SMS-201-995 on rectal fluid volume and electrolyte loss, and local and general prostanoid production were compared with those of treatment with indomethacin. During treatment with the somatostatin analogue iso-osmolar rectal fluid production increased about 25%; the quantity of prostaglandin E2 in the rectal fluid rose almost 20-fold. Prostaglandin F2 alpha, 6-keto-prostaglandin F1 alpha and 13,14-dihydro-15-keto-prostaglandin F2 alpha output showed similar, though less impressive increments during somatostatin treatment. The somatostatin analogue did not affect urinary prostanoid excretion except for levels of 2,3-dinor-thromboxane B2, which doubled. With indomethacin treatment diurnal rectal fluid production dropped by about 50% and all prostanoids measured in urine and rectal fluid decreased below control values. It appears that the somatostatin analogue SMS-201-995 has a marked stimulatory effect on the in vivo prostanoid production by the villous adenoma. Perhaps this stimulation is not confined to the tumor only, but also affects thromboxane synthesis.

Therapeutic strategies in the management of endocrine GEP tumours

The therapeutic principles in the management of endocrine gastroenteropancreatic (GEP) tumours include surgical extirpation of the primary tumour in the absence of metastases and medical control of symptoms in the preoperative phase. In the presence of metastases only palliative procedures are available. Tumour growth might be controlled by surgical procedures as debulking of tumour masses, medically by chemotherapy and more recently by new developments as a long-acting somatostatin analogue (SMS 201-995) and alpha-interferon. Their efficacy is currently evaluated in prospective studies. In contrast to inhibition of growth symptoms derived from excessive hormone production by GEP tumours can be well controlled. SMS 201-995 effectively prevents or at least improves flush and diarrhoea in the carcinoid syndrome, disabling diarrhoea in the Verner-Morrison syndrome and migratory erythema in the glucagonoma syndrome. SMS acts by inhibition of hormone release from the tumour and by a direct mechanism at the site of the target cell via SMS receptors present on tumour and target cells. For control of acid hypersecretion in gastrinoma patients omeprazole is superior to all former and present alternatives and replaced total gastrectomy completely. A similarly effective drug to prevent hypoglycaemia due to uncontrolled insulin release from insulinomas is not available since neither SMS nor diazoxide are effective in every insulinoma patient.

Severe posthemicolectomy diarrhea: evaluation and treatment with SMS 201-995

The effect of subcutaneous somatostatin analogue SMS 201-995 (Sandoz Pharmaceuticals Corp., East Hanover, NJ) was investigated in a patient with acute postoperative secretory diarrhea. The patient was hospitalized with bowel obstruction caused by a descending colon adenocarcinoma. One week after left hemicolectomy and transverse colostomy, watery colostomy output, which exceeded 10 L per day developed. Jejunal perfusion studies suggested that the patient's diarrhea was caused by abnormal net secretion of water and electrolytes by the small intestine. Circulating levels of various peptide hormones were normal with the exception of elevated level of pancreatic polypeptide. SMS 201-995 administration reduced colostomy output and normalized many of the abnormalities found during jejunal perfusion. These results indicate that the patient's acute secretory diarrhea, occurring after large intestinal obstruction, originated in the small intestine and that SMS 201-995 can be used to manage this unusual severe postoperative problem.

Clinical response to the long acting somatostatin analogue SMS 201-995 in a child with congenital microvillus atrophy

A 27 month old girl with congenital microvillus atrophy received two courses of SMS 201-995, a synthetic long acting analogue of native somatostatin, in an attempt to decrease profuse secretory diarrhoea. During the first trial at 13 months of age fluid and electrolytes administered by parenteral infusion were decreased as measured by water and faecal electrolyte losses. During the second trial of SMS 201-995 at 19 months fluid and electrolyte input were held constant for 14 days. Stool volume declined from 275 ml/kg to 161 ml/kg. Reductions in output of stool electrolytes (Na+, K+, Cl-) were accompanied by an increase in urine fluid output and increased excretion of urinary Na+. Subsequent administration of SMS 201-995 for a nine month period was not associated with adverse side effects or an impairment of growth velocity. These findings suggest that SMS 201-995 may be useful therapy in infants with high output diarrhoea as a result of congenital microvillus atrophy.

Intravenous and subcutaneous administration of a long-acting somatostatin analogue: effects on glucose metabolism and splanchnic haemodynamics in healthy subjects

The effect of SMS 201-995, a long-acting somatostatin analogue, on splanchnic blood flow and glucose metabolism, was investigated in five groups of healthy subjects. Groups A (n = 4), B (n = 5), C (n = 5) and D (n = 5) were studied before, during and after a 60-min intravenous infusion of SMS (1.7, 0.8, 0.2 and 0.1 micrograms min-1, respectively). Group E (n = 6) was investigated before and for 6 h after a subcutaneous injection of 25 micrograms of SMS. The splanchnic blood flow decreased by 20-25% in all groups in response to SMS and remained low during the entire observation periods. Arterial concentrations of glucose showed a 15-20% decline during SMS infusion in Groups A and B (P less than 0.05-0.01) and a less pronounced decrease in the other groups. Fifteen minutes after the end of infusion the glucose levels started to rise and in group A, the levels were significantly higher than basal (+25%, P less than 0.05-0.01) at 90-180 min after the end of infusion. The net splanchnic glucose production, determined in groups A and B, decreased by 65-75% in response to SMS infusion. Towards the end and immediately after the infusions, however, the net glucose output increased, but decreased again at 30-60 min after the end of infusion. Arterial, insulin and glucagon concentrations decreased significantly during infusion in all groups. This decline was more pronounced for insulin (50%) than for glucagon (20-25%) and insulin concentrations remained low for a longer period after the end of infusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of long-acting somatostatin analog SMS 201-995 in patients with pancreatic islet cell tumors

Natural somatostatin reduces plasma concentrations of many peptides, and is of short term benefit in patients with islet cell tumors, but has to be given as a continuous intravenous infusion. We review the published experience with the long acting synthetic somatostatin analogue SMS 201-995 in patients with islet cell tumors. Fifteen of 18 patients with vasoactive intestinal peptide-producing tumors, 8 of 8 patients with glucagonomas, 7 of 7 patients with unresectable insulinomas, and 3 of 3 patients with growth hormone releasing factor-producing tumors had a good sustained symptomatic response to SMS 201-995. Patients with benign insulinomas responded variably and are best treated by surgery. Patients with gastrinomas are best treated by oral gastric antisecretory agents. In all these syndromes, the clinical response to SMS 201-995 did not necessarily parallel the change in plasma concentration of marker peptide, suggesting that SMS 201-995 may have actions at various sites. The effect of SMS 201-995 on tumor size has been assessed in 46 patients, less than 20% of whom showed a reduction in tumor size. Side effects have been mild, but include steatorrhea and gastrointestinal disturbances. More studies will be required to fully assess the effects of long-term administration of SMS 201-995.

In vitro effects of the long-acting somatostatin analogue SMS 201-995 on electrolyte transport by the rabbit ileum

We have investigated the in vitro properties of SMS 201-995, a long-acting somatostatin analogue, on electrolyte transport in rabbit ileum. Similar to native somatostatin, serosal addition of this compound inhibits electrogenic anion secretion and stimulates neutral sodium and chloride absorption. Both compounds have similar maximal effects on ion transport; however, the ED50 of SMS 201-995 (2.4 X 10(-10) M) was 60 times less than that for somatostatin. In addition, unlike somatostatin, no inherent tachyphylaxis was observed in response to SMS 201-995. The antisecretory profile of SMS 201-995 was also compared with that of epinephrine. Unlike treatment with epinephrine, pretreatment of tissues with SMS 201-995 did not directly inhibit electrogenic anion secretion stimulated by vasoactive intestinal polypeptide, calcium ionophore A23187, and bethanechol. In contrast, this agent blocked vasoactive intestinal polypeptide and bethanechol inhibition of net sodium absorption. We conclude that SMS 201-995 has several unique in vitro properties that may explain its greater biologic activity compared with that of somatostatin. Its effects on secretagogue-stimulated electrogenic anion secretion and electroneutral NaCl absorption appear to differ.

Pathophysiological study of diarrhoea in a patient with medullary thyroid carcinoma. Evidence against a secretory mechanism and for the role of shortened colonic transit time

Intubation techniques and scintigraphic studies were used to determine the origin and mechanism of diarrhoea in a patient with medullary thyroid carcinoma, high plasma immunoreactive calcitonin and normal circulating serotonin, substance P and prostaglandins E2 and F2 alpha. Normal function of the small intestine was found for the following: (a) absorption tests; (b) water and electrolyte absorption in the proximal jejunum; (c) 24 hour flow rate and composition of fluid entering the colon and (d) gastric emptying rate and small intestinal progression of a normal meal. By contrast, colonic function was markedly impaired in three ways: (a) water absorption was decreased by half; (b) as the main excreted solutes were organic acids, a large electrolyte gap was recorded in faecal water, and (c) colonic transit time of the meal marker was very short, and was in agreement with the rapid transit of ingested radioopaque markers. These data strongly suggest that decreased absorption in the colon secondary to a motor disturbance is the main mechanism of diarrhoea in this case of medullary thyroid carcinoma, while calcitonin induced small intestinal fluid secretion suggested earlier is either non-existent, or only of minor importance.

Pancreatic cholera syndrome due to a vasoactive intestinal polypeptide-producing tumor: further insights into the pathophysiology

This case report describes a patient with pancreatic cholera caused by a vasoactive intestinal polypeptide-producing pancreatic tumor. The case presents several unusual characteristics of this disease. The primary tumor was a mucinous adenocarcinoma of the pancreas. The serum vasoactive intestinal polypeptide level of 2400 pmol/L is the highest reported. At this vasoactive intestinal polypeptide level, the somatostatin analogue SMS 201-995 at doses up to 2 mg/24 h did not control the 21 L/24 h stool output. Fecal incontinence due to a manometrically documented hypotonic internal anal sphincter occurred. Using surgically created stomas, the segmental gastrointestinal fluid and sodium losses were shown to be greatest from the jejunum, whereas potassium losses from the colon and small intestine were equal. The cellular mechanism for the small intestinal potassium secretion is not known.

Tumor regression of an ileal carcinoid under the treatment with the somatostatin analogue SMS 201-995

A 53-year-old man with metastatic ileal carcinoid ultimately failed to respond to conventional measures of surgery and was finally treated with a new long acting somatostatin analogue, SMS 201-995 for 7 months. SMS 201-995 not only gave symptomatic relief but also induced a reduction in metastatic tumor mass.

Successful treatment of idiopathic secretory diarrhea of infancy with the somatostatin analogue SMS 201-995

The somatostatin analogue SMS 201-995 has been reported to be effective in treating adult secretory diarrhea due to vasoactive intestinal polypeptidoma. We report the effectiveness of this drug in treating severe refractory secretory diarrhea of uncertain etiology in an infant. The patient developed diarrhea within the first few days of life, with mean stool output of 250 ml/kg.day (expected 10 ml/kg.day). Small bowel biopsy showed mild focal enteritis. Serum levels of known gastrointestinal secretagogues were normal. No tumor was detected. Diarrhea was not adequately controlled by various drug treatments. Addition of subcutaneous SMS 201-995 produced a significant sustained decrease in stool output to 80-100 ml/kg.day. During SMS 201-995 treatment, no metabolic, hormonal, or growth abnormalities were noted. SMS 201-995 was discontinued after 9 mo because of patient irritability. Stool output rose immediately to 173 ml/kg.day, and remained stable for 6 mo. It is concluded that SMS 201-995 was a safe and effective treatment in this single childhood case of severe idiopathic secretory diarrhea.

Cardiovascular effects of vasoactive intestinal peptide in healthy subjects

Hypotension and flushing are occasionally observed in patients with pancreatic cholera syndrome. Similar effects are produced when vasoactive intestinal polypeptide (VIP) is administered to healthy subjects. To characterize further these responses, serial measurements of heart rate, blood pressure, cardiac output and forearm blood flow were made in 6 healthy subjects during constant VIP infusion (400 pmol/kg/hr for 100 minutes). VIP infusion caused sustained vasodilatation and decreased total peripheral resistance and mean arterial pressure by 30 and 12%, respectively. Forearm resistance decreased by 65%. The effects on cardiac output and stroke volume were biphasic. During the early phase of VIP infusion (0 to 70 minutes), heart rate and cardiac output increased with only minor changes in stroke volume. Later (71 to 100 minutes) the tachycardia persisted, but cardiac output decreased toward control levels due to decreased stroke volume. Echocardiograms during the infusion demonstrated increased left ventricular contractility as defined by the relation between end-systolic wall stress and shortening fraction. These data document potent vasodilatory and inotropic actions of VIP. It is likely that intravascular volume losses from increased intestinal secretion account for the decreased stroke volume seen late in the VIP infusion period and immediately thereafter. The tachycardia appears to be an appropriate compensatory mechanism to maintain blood pressure in the presence of vasodilatation and loss of intervascular volume. These observations provide an explanation for the cardiovascular findings in patients with sudden release of VIP from tumors.

Effect of somatostatin analog on water and electrolyte transport and transit time in human small bowel

The present study was undertaken to investigate how a somatostatin analog (201-995 Sandoz), which is now commonly used for treatment of patients with gut hormone-producing tumors, affects water and ion absorption and transit time in the normal jejunum. Six healthy volunteers were given somatostatin analog intravenously at a dose of 1 microgram/kg/hr. At the same time, jejunal water and ion movement and transit time were measured using the triple-lumen tube technique [perfusion of a plasma-like electrolyte solution with PEG as a nonabsorbable marker at a rate of 15 ml/min; dye dilution curves ([3H]mannitol, [14C]PEG, BSP) for determination of jejunal transit time]. During somatostatin analog administration, transit time through a 30-cm segment of perfused jejunum increased from 4.0 min to 17.0 min. While the somatostatin analog increased jejunal transit time, it had no effect on net water and electrolyte absorption under steady-state conditions. The effect of somatostatin analog on the proximal small bowel is similar to the action of an eight-times higher dose of intravenous native somatostatin previously studied. The effect of the analog on transit time suggests a potentially beneficial effect in patients with large-volume diarrhea in which no tumor or circulating secretagogue can be identified, such as in pseudopancreatic cholera syndrome.

VIPoma syndrome

Since the description of the watery diarrhea syndrome by Verner and Morrison 29 years ago, clinical and experimental observations have elucidated the pathophysiology of this disease. Vasoactive intestinal polypeptide (VIP) is produced and released by a tumor of the pancreatic islets or by a tumor of neural crest origin such as a ganglioneuroma. Under normal conditions, current evidence suggests that VIP is a neurotransmitter in the central and peripheral nervous systems and particularly in the peptidergic nervous system. The low VIP plasma concentration observed in healthy subjects is viewed as a neuronal overflow since it has been impossible to ascertain any endocrine role for circulating VIP. Markedly elevated VIP plasma levels in the VIPoma syndrome lead to intestinal secretion with severe secretory diarrhea, resulting in hypovolemia, hypokalemia, and acidosis. These symptoms subside after successful tumor removal. Approximately 50 percent of patients have metastatic spread at the time of diagnosis. For these patients, a new and promising therapeutic modality is available in the form of a subcutaneously administered somatostatin analogue that relieves symptoms through potent inhibition of VIP release from tumor tissue.

Clinical and hormonal effects of a long-acting somatostatin analogue in pancreatic endocrine tumors and in carcinoid syndrome

Nine patients with pancreatic apudomas (seven gastrinomas, one glucagonoma, one tumor secreting a substance P-like component) and nine with metastasized carcinoid tumors were treated with a somatostatin analogue (SMS 201-995), administered subcutaneously twice daily for 3 days. Treatment was pursued for 2 to 12 months in nine patients in whom SMS was clinically and/or biologically beneficial. In gastrinomas, SMS decreased plasma gastrin in all but one patient, inhibited the residual gastric acid secretion under H2-blockers and improved diarrhea; in the glucagonoma patient, glucagonemia decreased and skin lesions disappeared. In carcinoid syndrome, clinical efficacy was partial and inconstant; daily 5-hydroxyindole acetic acid (5-HIAA) output was slightly decreased. Plasma substance P levels decreased in six patients with initially high concentrations. No antitumoral activity or side effects have been so far evidenced. SMS 201-995 is a useful, well-tolerated agent in secreting pancreatic apudomas and to a lesser extent in carcinoid syndrome, where high-dosage regimens may be required.

Somatostatin analogue SMS 201-995 long term therapy for vipoma

The definitive treatment of a pancreatic tumour secreting vasoactive intestinal polypeptide is surgical removal of the tumour, but when curative resection is not possible symptomatic treatment of the endocrine hyperfunction is important. Streptozotocin, although effective for palliation, can involve unpleasant side effects. We report the long term use of subcutaneous somatostatin analogue SMS 201-995 in an elderly man presenting with severe watery diarrhoea and anaemia due to a pancreatic vipoma. Good symptomatic improvement has been achieved with no side effects over a period of 24 months. We suggest there is a use for subcutaneous SMS 201-995 in elderly patients with inoperable pancreatic gut hormone producing tumours with metastases and in those where surgery would carry a high operative risk.

Escape of the response to a long-acting somatostatin analogue (SMS 201-995) in patients with VIPoma

Two patients with severe secretory diarrhea due to metastatic vasoactive intestinal peptidoma were treated with a synthetic somatostatin analogue in an attempt to control the patients' vasoactive intestinal peptide-related symptoms. In both patients, a good initial response to this treatment could be demonstrated; not only did diarrhea subside but there was also a dramatic fall in vasoactive intestinal peptide plasma levels. However, after 11 and 4 days respectively, diarrhea recurred accompanied by a rise in vasoactive intestinal peptide plasma levels. In fact, under treatment with the somatostatin analogue and with natural somatostatin, a significant rebound state was observed regarding diarrhea as well as vasoactive intestinal peptide levels, which caused considerable difficulty in the clinical management in 1 patient. This patient had to undergo surgery. In the second patient, the responsiveness to somatostatin analogue returned a few days after discontinuation of the treatment, lasting, however, for a short period only. The possible mechanism of this escape and rebound with somatostatin treatment is discussed.

Antidiarrheal therapy. Prospects for new agents

Successful treatment of severe diarrhea has traditionally relied upon opiates or opiate derivatives. Recent advances in our understanding of intestinal fluid and electrolyte absorption have provided the opportunity to develop therapeutic agents specific for various points in the secretory and absorptive process. Present and proposed antidiarrheal agents, in addition to antimotility activity, will be capable of stimulating intestinal fluid absorption, inhibiting intestinal fluid secretion, or both. The mechanism(s) of action and clinical implications for proposed antidiarrheal agents are reviewed.