Small doses of the unabsorbable substance polyethylene glycol 3350 accelerate oro-caecal transit, but slow gastric emptying in healthy subjects

Effects of medicines used to treat gastrointestinal diseases on the pharmacokinetics of coadministered drugs: a PEARRL Review

Objectives

Drugs used to treat gastrointestinal diseases (GI drugs) are widely used either as prescription or over-the-counter (OTC) medications and belong to both the 10 most prescribed and 10 most sold OTC medications worldwide. The objective of this review article is to discuss the most frequent interactions between GI and other drugs, including identification of the mechanisms behind these interactions, where possible.

Key findings

Current clinical practice shows that in many cases, these drugs are administered concomitantly with other drug products. Due to their metabolic properties and mechanisms of action, the drugs used to treat gastrointestinal diseases can change the pharmacokinetics of some coadministered drugs. In certain cases, these interactions can lead to failure of treatment or to the occurrence of serious adverse events. The mechanism of interaction depends highly on drug properties and differs among therapeutic categories. Understanding these interactions is essential to providing recommendations for optimal drug therapy.

Summary

Interactions with GI drugs are numerous and can be highly significant clinically in some cases. While alterations in bioavailability due to changes in solubility, dissolution rate, GI transit and metabolic interactions can be (for the most part) easily identified, interactions that are mediated through other mechanisms, such as permeability or microbiota, are less well-understood. Future work should focus on characterising these aspects.

Stimulating fermentation by the prolonged acceleration of gut transit protects against decompression sickness

Massive bubble formation after diving can lead to decompression sickness (DCS). Gut fermentation at the time of a dive exacerbates DCS due to endogenous hydrogen production. We sought to investigate whether medium-term stimulation of fermentation as a result of polyethylene glycol (PEG)-induced acceleration of bowel transit before diving exacerbates DCS in rats. Seven days before an experimental dry dive, 60 rats were randomly divided in two groups: an experimental group treated with PEG (n = 30) and an untreated control group (n = 30). Exhaled hydrogen was measured before the dive. Following hyperbaric exposure, we assessed for signs of DCS. After anaesthetisation, arterial blood was drawn to assay inflammatory cytokines and markers of oxidative stress. PEG led to a significant increase in exhaled H₂ (35 ppm [10–73] compared with control 7 ppm [2–15]; p = 0.001). The probability of death was reduced in PEG-treated rats (PEG: 17% [95% CI 4–41] vs control: 50% [95% CI 26–74]; p = 0.034). In addition, inflammatory markers were reduced, and the antioxidant activity of glutathione peroxidase was significantly increased (529.2 U.l⁻¹ [485.4–569.0] versus 366.4 U.l⁻¹ [317.6–414.8]; p = 0.004). Thus, gut fermentation might have a positive effect on DCS. The antioxidant and neuroprotective properties of the fermentation by-products H₂ and butyrate may explain these results.

Split-dose bowel preparation with polyethylene glycol for colonoscopy performed under propofol sedation. Is there an optimal timing?

OBJECTIVE

Aspiration risk, especially with propofol sedation, remains a concern after split-dose bowel preparation of up to 1 L polyethylene glycol for the procedure. We aimed to identify the ideal timing of bowel preparation to achieve optimal colon cleansing with no increased risk of aspiration.

METHODS

A total of 892 consecutive patients undergoing simultaneous esophagogastroduodenoscopy (EGD) and colonoscopy were prospectively recruited. Residual gastric volume (RGV) and pH of gastric contents were measured at EGD, and patients' characteristics, runway time (duration between completion of the final liter of bowel preparation and colonoscopy commencement), and cleansing quality were recorded.

RESULTS

A shorter runway time resulted in better colon cleansing (r = -0.124, P < 0.001). No correlation between runway time and RGV or pH was found (r = -0.017, P = 0.62 and r = -0.030, P = 0.47, respectively). RGV and pH did not differ significantly with runway time of 4 or 5 h. RGV with runway time ≤3 h was 35.9 ± 11.8 mL and 17.4 ± 0.6 mL after runway time >3 h (P < 0.001). No aspiration pneumonia occurred. The only factors independently related to higher RGV were younger age and male sex.

CONCLUSIONS

The consumption of bowel preparation agent within 3-4 h before propofol sedation resulted in a similar RGV and pH as those achieved by more prolonged fasting, with no increased risk of aspiration even in patients perceived to be at high risk.

Measurement of Gastrointestinal and Colonic Motor Functions in Humans and Animals

Accurately measuring the complex motor behaviors of the gastrointestinal tract has tremendous value for the understanding, diagnosis and treatment of digestive diseases. This review synthesizes the literature regarding current tests that are used in both humans and animals. There remains further opportunity to enhance such tests, especially when such tests are able to provide value in both the preclinical and the clinical settings.

Split-dose sodium picosulfate-magnesium citrate colonoscopy preparation achieves lower residual gastric volume with higher cleansing effectiveness than a previous-day regimen

BACKGROUND AND AIMS

It is known that sodium picosulfate-magnesium citrate (SPMC) bowel preparations are effective, well tolerated and safe, and that split-dosing is more effective for colon cleansing than previous-day regimens. Anesthetic guidelines consider that residual gastric fluid is independent of clear liquid fasting times. However, reluctance to use split-dosing persists. This may be due to limited data on residual gastric fluid volumes (RGFVs) and split-dosing bowel preparations, and that these may not be perceived as standard clear liquids. Furthermore, no studies are available on RGFV/residual gastric fluid pH (RGFpH) and SPMC. We aimed to evaluate the cleansing effectiveness and the RGFV/RGFpH achieved after an SPMC split-dosing regimen compared with a SPMC previous-day regimen.

METHODS

This was a single-center observational study. A total of 328 outpatients scheduled for simultaneous EGD and colonoscopy and following a split-dosing or previous-day regimen of SPMC were included. We prospectively measured colon cleanliness by using the Ottawa Bowel Preparation Scale, RGFV, and RGFpH.

RESULTS

Ottawa Bowel Preparation Scale scores for overall, right, mid-colon, and colon fluid were significantly better in the split-dosing group. In the split-dosing group, the 3- to 4-hour fasting time consistently achieved the best cleansing quality. RGFV was significantly lower in the split-dosing group (11.09 vs 18.62, P < .001). No significant differences in RGFpH were detected.

CONCLUSIONS

Split-dosing SPMC provides higher colon cleansing quality with lower RGFVs than previous-day SPMC regimens. SPMC in split-dosing acts exactly as a standard clear liquid acts, and thus anesthetic guidelines on this issue may be applied with no concerns.

Rapid colonoscopy preparation using bolus lukewarm saline combined with sequential posture changes: a randomized controlled trial

OBJECTIVE

In this randomized clinical trial, we have compared the Shudh™ colon cleanse (SCC) with HalfLytely(®) colon prep (HCP) to evaluate the efficacy, bowel preparation time (BPT), adverse events, electrolyte abnormalities and patient acceptability.

METHODS

Patients were randomized to receive either SCC (n = 65) or HCP (n = 68). All colonoscopies were performed by a single, blinded endoscopist. Colon prep was evaluated on a 5 point grading scale. Statistical non-inferiority was pre-defined as a difference of <15 % in the lower limit of the 95.5 % confidence interval for the treatment difference. Data that were collected include bowel prep score, BPT, adverse events, electrolyte abnormalities and patient acceptability.

RESULTS

Bowel preparation efficacy was rated as "successful" for 59/65 (90.7 %) in SCC versus 66/68 (97.1 %) in HCP. This gave a success difference of -6.4 % with a 1-sided 95 % lower confidence limit (LCI) for the difference = -13.3 % (non-inferiority p = 0.25). This difference fell within the predefined limit for non-inferiority. The average BPT for SCC was 1.9 h versus 10.9 in HCP (p < 0.001). No serious adverse events were reported in either group. None of the patients in either group had any clinically significant electrolyte imbalance. Patient ratings for palatability and willingness to repeat were significantly better for SCC (p < 0.05).

CONCLUSION

SCC was found to not be inferior to PEG with regards to the quality of bowel preparation. It is worth highlighting that a major advantage of SCC is shorter BPT.

Laxative treatment with polyethylene glycol does not affect lipid absorption in rats

OBJECTIVES

Polyethylene glycol (PEG) is a frequently used laxative agent. It is unknown, however, whether PEG affects the absorptive capacity of the intestine. Reduced lipid (dietary fat and cholesterol) absorption induced by long-term PEG treatment could negatively affect growth in children. We tested whether PEG accelerates gastrointestinal transit and alters lipid absorption and plasma lipid levels.

METHODS

Wistar rats were administered drinking water with or without PEG (7%) for 2 weeks. We studied whole gut transit time by recording the first appearance of red feces after intragastric carmine red administration. We measured plasma concentrations of cholesterol and triglycerides, dietary fat absorption by 48-hour fat balance and by plasma appearance of intragastrically administered stable-isotope labeled fats, and cholesterol absorption with a dual stable isotope technique.

RESULTS

PEG decreased whole gut transit time by 20% (P=0.028) without causing diarrhea. PEG treatment did neither affects overall dietary fat balance nor fat uptake kinetics, cholesterol absorption, or plasma lipid concentrations.

CONCLUSIONS

PEG does not affect lipid absorption nor steady-state plasma lipid levels in rats, although it accelerates the gastrointestinal transit.

Methods for the assessment of small-bowel and colonic transit

Transit assessment of the small intestine and colon is relevant in the study of physiology, pathophysiology, and pharmacodynamics, and there is increasing use of small-bowel and colonic transit measurements in clinical practice as well. The main methods that are applied in clinical practice are substrate-hydrogen breath tests for small-bowel transit and radiopaque markers for colonic transit. Over the past 2-3 decades, scintigraphy has become the preferred standard in research studies, particularly for studies of pathophysiology and pharmacodynamics. New approaches include experimental stable isotope measurement of orocecal transit and the recently approved method using a wireless motility capsule that is validated as an accurate measurement of small-bowel and colonic transit.

A randomized, double-blind, placebo-controlled trial of polyethylene glycol effects on fasting and postprandial rectal sensitivity and symptoms in hypersensitive constipation-predominant irritable bowel syndrome

AIM

To assess the effect of polyethylene glycol 3350 (PEG) on fasting and postprandial (PP) perception of rectal distension and symptoms in hypersensitive constipation-predominant irritable bowel syndrome (IBS-C).

METHODS

Forty-two patients meeting Rome II criteria for IBS-C and with a pain threshold of < 32 mmHg were included in a randomized, double-blind, placebo-controlled trial. Patients received either oral PEG, 3.45 g t.i.d. orally for 30 days or placebo. Rectal sensitivity was assessed before and after treatment with a barostat using the ascending method of limits, during basal and PP periods.

RESULTS

No changes in fasting and PP rectal tone and thresholds for first sensation, gas sensation, urge to defecate, and pain was observed with PEG in relation to placebo. In both groups, pressure at which patients crossed the thresholds for noxious (PEG: from 28 ± 8.8 to 22 ± 6.9 mmHg) and non noxious (PEG: from 16 ± 4.9 to 12 ± 3.6 mmHg) stimuli decreased compared with pretreatment values. PEG improved consistency of faeces and showed a trend to diminish blood in faeces. PEG and placebo increased bowel movements per week (P < 0.001), and relieved symptoms without significant side-effects.

CONCLUSIONS

Both PEG 3350 and placebo were clinically useful in patients with IBS-C, an effect that cannot be explained by changes in rectal tone and sensation. The results support the concept that visceral sensitivity is not stable and has a heterogeneous response to drugs, and suggest the existence of a post healing hypersensitivity state.

The inulin hydrogen breath test accurately reflects orocaecal transit time

BACKGROUND

The lactose[(13)C]ureide breath test ((13)C-LUBT) has been validated and established as a reliable, non-invasive test for the assessment of orocaecal transit time (OCTT). More recently, small studies have demonstrated that inulin could be an alternative substrate for H(2)-based breath testing of the small bowel transit (H(2)-INBT). We compared the performance of the H(2)-INBT with the (13)C-LUBT in an appropriate number of participants, determined by sample-size calculation.

DESIGN

Twenty-nine people underwent a combined (13)C-LUBT/H(2)-INBT. Five Hundred mg of lactoseureide was ingested on the day before the test to induce an adequate enzyme activity in colonic bacteria. For the test, they received 500 mg of lactose[(13)C]ureide and 5 g inulin, dissolved in 400 mL of a standard enteral liquid nutrition orally. Breath samples were collected every 30 min for 8 h and analysed for H(2)[ p.p.m.] and (13)CO(2)-enrichment [delta-(13)C]. For the (13)C-LUBT, the OCTT was defined as the interval with an increase of delta > 2.5SD above the running average of all previous points. The latter was defined as a rise of > 10ppm above baseline regarding the H(2)-INBT.

RESULTS

Breath tests produced evaluable data in 27/29 patients [93%]. Median OCTTs were 315 min (range 210-450 min) for the (13)C-LUBT and 300 min (180-420 min) for the H(2)-INBT (P = 0.15). The (13)C-LU-OCTT correlated well with the H(2)-IN-OCTT (r = 0.72). Bland-Altman blot showed that the mean H(2)-IN-OCTTs were approximately 30 min shorter than predicted with the (13)C-LUBT.

CONCLUSIONS

Inulin is a reliable and inexpensive substrate for a hydrogen-based assessment of the OCTT. In contrast to the (13)C-LUBT, the H(2)-INBT does not require patients to refrain from physical activity and may additionally increase its acceptance for clinical purposes.

Evaluation of polyethylene glycol plus electrolytes in the treatment of severe constipation and faecal impaction in adults

INTRODUCTION

Extreme and severe cases of constipation can lead to faecal impaction. Current therapies are often both ineffective and unpleasant. The objective of this trial was to evaluate the efficacy and safety of Movicol, a polyethylene glycol (PEG) + electrolyte solution (PEG+E), as treatment for severe constipation and faecal impaction.

PATIENTS

56 patients (aged 17 to 88 years) with a history of chronic constipation and presenting with no bowel movement for three to four days (severe constipation), or no bowel movement for at least five days (faecal impaction), were enrolled at three centres in Taiwan. Faecal loading was confirmed in all patients by abdominal and rectal examination or abdominal radiography. Patients were excluded from the study if they had a gastrointestinal obstruction, evidence of delayed gastric emptying, or if their constipation was secondary to severe inflammatory bowel disease.

TREATMENT

All patients followed the same regimen: up to eight 13.8 g sachets of PEG+E (two at a time in 250 ml water; maximum of 1L/day) over a 4-6 h period each day, with 1-1.5 h between each dosing. Duration of treatment was for up to three days. EFFICACY ENDPOINTS AND RESULTS: Patients with either improvement (passage of a moderate to large volume of stool within four days of treatment initiation) or complete resolution (passage of moderate to large volumes of faecal matter plus the disappearance of palpable faecal masses in the abdomen and/or rectum) were considered responders. Based on bowel movement data recorded by the patients, an excellent response rate was obtained: 50/56 patients had a successful response to treatment (89.3%; 95% confidence intervals [CIs] 77.4% to 95.6%); there were 39 complete responders and 11 patients showed improvement. Investigator assessment of response was almost the same: 87.5% (95% CIs 75.3% to 94.4%). All bowel movement measurements (stool volume, number of evacuations, stool form and ease of evacuations) showed a positive improvement by Day 2. Median duration of treatment was two days. The incidence of adverse events was low, even for those side-effects such as abdominal pain and bloating, which are known undesirable consequences of PEG+E administration. No patient discontinued from the study because of an adverse event.

CONCLUSION

PEG+E, administered orally at a dose equivalent to eight 13.8 g sachets (1 L) per day over three days, was a highly effective and well tolerated therapy for the treatment of severe constipation and faecal impaction.

Measurement of gastric emptying by octanoate metabolism

PURPOSE OF REVIEW

Since its introduction just over 10 years ago, there have been a number of studies that have used the octanoate breath test to assess gastric emptying. Although use of the method is on the increase (the number of gastric emptying studies published on PubMed using the octanoate breath test has doubled between the periods 1997-2000 and 2001-2004 compared with a drop of approximately 20% in the use of scintigraphy over the same periods), the methodology has not achieved universal acceptance, primarily because it can provide results comparable to established techniques only indirectly.

RECENT FINDINGS

Recent methods for overcoming this difficulty are reviewed, including modified methods for breath test interpretation and the application of the related saliva test. The latter promises to be useful as a non-invasive proxy for established techniques, such as scintigraphy, for further validation of the breath test. Recent applications of octanoate-based methods are briefly considered.

SUMMARY

A novel approach detailed in this review for breath test interpretation, where the bicarbonate pool is modelled as a single compartment, could prove useful for obtaining breath test gastric emptying parameters that are directly comparable with those obtained from the gold standard, gamma scintigraphy. In combination with the saliva test, this could add credence to use of the octanoate breath test as a clinically accepted diagnostic tool, in addition to its potential in research.