The effect of sildenafil on lower esophageal sphincter and body motility in normal male adults

Phosphodiesterase 5 (PDE-5) inhibitors (sildenafil, tadalafil, and vardenafil) effects on esophageal motility: a systematic review

BACKGROUND

Esophageal motility disorders are a group of disorders associated with dysfunctional swallowing resulting from impaired neuromuscular coordination. Phosphodiesterase 5 (PDE-5) inhibitors induce smooth relaxation and are proposed as a treatment option for esophageal motility disorders such as achalasia.

METHODS

This study is conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We systematically searched MEDLINE/ PubMed, Scopus, EMBASE, and Web of Science databases for esophageal outcomes of individuals treated with PDE5 inhibitors. A random effect meta-analysis was conducted.

RESULTS

A total of 14 studies were included. They were conducted in different countries, with Korea and Italy having the highest number of articles. The main drug assessed was sildenafil. PDE-5 inhibitors resulted in a significant reduction in lower esophageal sphincter pressure (SMD - 1.69, 95% CI: -2.39 to -0.99) and the amplitude of contractions (SMD - 2.04, 95% CI: -2.97 to -1.11). Residual pressure was not significantly different between the placebo and sildenafil groups (SMD - 0.24, 95% CI: -1.20 to 0.72). Furthermore, a recent study reported contractile integral, stating that ingestion of sildenafil leads to a significant reduction in distal contractile integral and a significant increase in proximal contractile integral.

CONCLUSION

PDE-5 inhibitors significantly reduce LES resting pressure and esophageal peristaltic vigor, decreasing esophageal body contractility and contraction reserve. Therefore, using these drugs in patients affected by esophageal motility disorders may potentially improve their condition regarding symptom relief and prevention of further associated complications. Future reports investigating larger sample size is necessary in order to establish definite evidence regarding the efficacy of these drugs.

A randomized crossover study of compounded liquid sildenafil for treatment of generalized megaesophagus in dogs

OBJECTIVE

To determine whether delivery of compounded liquid sildenafil directly to the stomach of dogs with megaesophagus (ME) would affect esophageal clearance, regurgitation frequency, body weight, or quality of life.

ANIMALS

10 client-owned otherwise healthy dogs with stable ME.

PROCEDURES

A randomized crossover study was performed. Dogs received either sildenafil (1 mg/kg, PO, q 12 h) or a placebo for 14 days, followed by a 7-day washout period, then the opposite treatment for 14 days. Esophageal clearance time was assessed by means of videofluoroscopy prior to treatment and on day 1 of each treatment period. Owners maintained logs of regurgitation episodes and quality of life.

RESULTS

Compounded liquid sildenafil moved into the stomach during 21 of 30 (70%) videofluoroscopy sessions. Sildenafil resulted in a significant reduction in the number of regurgitation episodes (median, 3.5 episodes/wk; range, 0 to 14.5 episodes/wk), compared with baseline (median, 6.5 episodes/wk; range, 1.5 to 19.5 episodes/wk) and the placebo (median, 4 episodes/wk; range, 0 to 28 episodes/wk), and a significant increase in body weight (median, 22.05 kg; range, 6 to 26.3 kg), compared with baseline (median, 21.55 kg; range, 5.1 to 26.2 kg) and the placebo (median, 22.9 kg; range, 5.8 to 25.9 kg). There were no differences in esophageal clearance times or quality-of life-scores between sildenafil and placebo.

CLINICAL RELEVANCE

Although significant differences with placebo administration were identified, clinically relevant improvements were not seen with the use of compounded liquid sildenafil in dogs with ME.

Sexual Dysfunction in Patients With Chronic Gastrointestinal and Liver Diseases: A neglected Issue

INTRODUCTION

Normal sexual activity is an important determinant of quality of life. Unfortunately, several chronic health disorders are associated with an impaired sexual function.

OBJECTIVE

To provide coverage of the current literature on prevalence and pathophysiology of sexual dysfunction in patients with gastrointestinal and liver disorders METHODS: A Comprehensive review of the literature on the prevalence of sexual dysfunction in chronic gastrointestinal and liver disorders, assessing the underlying mechanism (s) was performed.

RESULTS

Many gastrointestinal disorders, either functional or organic, are associated with some degree of sexual dysfunction. The main pathogenic mechanisms are: (i) the disease itself causing fatigue, anxiety or depression with a potential alteration of self-esteem; (ii) worry of transmitting a potential infectious agent through sexual activity; (iii) alteration of the endocrine mechanisms which are necessary for normal sexual functioning; (iv) chronic pro- inflammatory conditions which may cause endothelial dysfunction and abnormal vascular responses; (v) iatrogenic.

CONCLUSION

Based on this review, a thorough evaluation of sexual function through validated questionnaires and/or psychological interviews with patients with chronic gastrointestinal disorders should be part of the clinical assessment in order to timely diagnose and possibly treat sexual dysfunction in this clinical setting. L Romano, L Granata, F Fusco, et al. Sexual Dysfunction in Patients With Chronic Gastrointestinal and Liver Diseases: A neglected Issue. Sex Med Rev 2021;XX:XXX-XXX.

Influence of sildenafil on esophageal motor function in humans: Studies using high-resolution manometry

BACKGROUND/AIM

Sildenafil induces smooth muscle relaxation of the esophagus by blocking type 5 phosphodiesterase that degrades cyclic guanine monophosphate. We aimed to characterize the effects of sildenafil on esophageal peristalsis and contraction reserve using high-resolution manometry (HRM).

METHODS

Fifteen healthy adults (12 men, age 21-39, mean 27 years) participated in this study using HRM following either sildenafil 50 mg or placebo. HRM with ten wet swallows and five multiple rapid swallows was performed in all participants. HRM metrics included esophagogastric junction contractile integral (EGJ-CI), basal lower esophageal sphincter (LES) pressure, 4-second integrated relaxation pressure (IRP-4s), distal contractile integral (DCI), distal latency, resting upper esophageal sphincter pressure (UESP), and the response to MRS.

RESULTS

Sildenafil significantly lowered EGJ-CI (P < .001), LES pressure (P = .04), IRP-4s (P = .02), and DCI (P < .001). There was no difference in UESP (P = .87) between sildenafil and placebo. Sildenafil significantly decreased peristaltic vigor, inducing absent peristalsis in 12 subjects and ineffective esophageal motility in 3 subjects. Peristaltic response and augmentation following MRS were significantly inhibited following sildenafil (7% vs 100%, P < .001, and none vs 73%, P < .001).

CONCLUSIONS

Sildenafil attenuates EGJ barrier function, resting LES pressure, and LES relaxation. Both esophageal body contractility and contraction reserve are inhibited by sildenafil in healthy adults.

Comparison of the therapeutic effects of sildenafil citrate, heparin and neuropeptides in a rat model of acetic acid-induced gastric ulcer

AIMS

The purpose of our investigative work has been to determine whether there can be therapeutic roles in the administration of sildenafil citrate, heparin and several neuropeptides on an animal model where gastric ulcers were induced with acetic acid, and to compare their efficacy.

MATERIALS AND METHODS

The animals were divided into 13 groups, with 4 animals in each. Gastric ulcers was induced in the animals of 12 groups with one untreated group being left as the control (Group I - control; given normal saline (NS)). The other groups were: Group II (ulcer+NS); Group III (5mg/kg sildenafil citrate, low dose); Group IV (10mg/kg sildenafil citrate, high dose); Group V (0.6mg/kg heparin, low dose); Group VI (6mg/kg heparin, high dose); Group VII (20nmol/kg des-acyl ghrelin); Group VIII (40nmol/kg des-acyl ghrelin); Group IX (4nmol/kg acyl ghrelin); Group X (8nmol/kg acly ghrelin); Group XI (20pmol/kg Nesfatin-1); Group XII (15nmol/kg Obestatin) and Group XIII (5nmol/kg Neuropeptide Y). Gastric neuropeptide expression was measured using an immunohistochemical method, and the amount in circulation was detected using ELISA. To compare with no treatment, the controls and other treatment groups, we recorded loss of the surface epithelium of the stomach, erosion, bleeding and inflammatory cell infiltration in the upper halves of the gastric glands.

KEY FINDINGS

The muscularis and the layers beneath it were, however, apparently normal. The gastric mucosa healed with little or no inflammation when sildenafil citrate, low dose heparin, ghrelin, NUCB2/Nesfatin-1, obestatin, Neuropeptide Y were administered.

SIGNIFICANCE

Overall the data indicate that low dose heparin, and especially sildenafil citrate and neuropeptides, can be used clinically as an alternative approach in the treatment of the gastric ulcer.

Sildenafil improves clinical signs and radiographic features in dogs with congenital idiopathic megaoesophagus: a randomised controlled trial

We evaluated the efficacy of oral sildenafil citrate in dogs with congenital idiopathic megaoesophagus (CIM). Twenty-one puppies were randomly assigned to two groups (treatment and control). The dogs were given sildenafil oral suspension 1 mg/kg every 12 hours for 14 days or placebo in a masked fashion. Clinical signs (frequency of regurgitation and weight gain) and oesophagrams (relative oesophageal diameter, ROD) were evaluated in order to assess the efficacy of drug treatment, by examiners who were unaware of the study protocol. In addition, a set of in vitro experiments on isolated samples of canine lower oesophageal sphincter (LOS) was performed, and the effects of increasing concentrations of sildenafil on basal tone and electrically-stimulated motility were assessed. Sildenafil administration significantly reduced the number of regurgitation episodes (0.88±1.40 v 2.65±1.56, P<0.0001) and significantly increased weight gain in the treated dogs compared to controls (79.76±28.30 per cent v 53.40±19.30 per cent, P=0.034). ROD values, at the end of the treatment period, were significantly decreased in the sildenafil group, compared to pre-treatment values (0.97±0.19 v 0.24±0.14, P<0.0001), in contrast to control subjects (0.98±0.17 v 1.10±0.25, P=0.480). In accordance with the in vivo findings, sildenafil dose-dependently reduced basal tone and increased electrically-induced relaxation of dog LOS samples. These results suggest that sildenafil citrate helps ameliorate clinical and radiographic signs in dogs with CIM by reducing LOS tone, and could represent a novel therapeutic tool for the treatment of this disease.

Examination of the effects of vardenafil on esophageal function using multichannel intraluminal impedance and manometry

Background/Aims

To evaluate the effects of the phosphodiesterase type 5 (PDE5) inhibitor vardenafil on esophageal function, including bolus transit, using multichannel intraluminal impedance and esophageal manometry (MII-EM).

Methods

Sixteen healthy volunteers (15 men) underwent an MII-EM study including 10 liquid swallows and 10 viscous swallows in a seated position after fasting. Then, each subject was asked to ingest 50 mL distilled water or 10 mg vardenafil dissolved in 50 mL water, in a double-blind manner. After 25 minutes, the MII-EM study was repeated.

Results

Eight men received vardenafil and eight subjects received water. Resting and residual lower esophageal sphincter pressures differed significantly only in the vardenafil group (from 18 ± 6.7 to 6.6 ± 5.3 mmHg, P < 0.001 and from 4.9 ± 2.6 to 2.1 ± 3.6 mmHg, P = 0.006, respectively). Mean distal esophageal amplitude decreased significantly only in the vardenafil group (from 86.7 ± 41.6 to 34.0 ± 38.0 mmHg, P < 0.05). Complete bolus transits of liquid and viscous meals decreased significantly only after vardenafil ingestion (from 80.2% ± 13.8% to 49.4% ± 27.9%, P < 0.05 and from 72.8% ± 33.6% to 21.5% ± 29.0%, P = 0.01, respectively).

Conclusions

Vardenafil decreased esophageal bolus transit in the seated position, despite decreased lower esophageal sphincter pressure.

Management of noncardiac chest pain in women

Noncardiac chest pain (NCCP) is very prevalent in the community. Although mortality remains low, morbidity and the financial implications are high. Women, especially those of middle age, should be thoroughly investigated as per current guidelines for coronary artery disease before labeling their chest pain as NCCP. Gastroesophageal reflux disease is the most common cause of NCCP; however other esophageal pathology including esophageal hypersensitivity, neuromuscular disease and eosinophilic esophagitis may also cause NCCP. Proton pump inhibitors are commonly used initially to manage NCCP, although patients who do not respond to this therapy require further investigation and differing treatment regimes. This article will focus on current knowledge regarding GI tract-related NCCP management strategies.

Effect of nitrite delivered in saliva on postprandial gastro-esophageal function

OBJECTIVE

Acid reflux produces troublesome symptoms (heartburn) and complications including esophagitis, Barrett's esophagus, and adenocarcinoma. Reflux occurs due to excessive and inappropriate relaxation of the lower esophageal sphincter. An important mediator of this is nitric oxide, high concentrations of which are generated within the lumen when swallowed saliva meets gastric acid. Saliva contains nitrite, derived from the enterosalivary recirculation of dietary nitrate, which is reduced to nitric oxide by gastric acid. The aim of this study was to investigate whether salivary nitrite contributes to dysfunction of the lower esophageal sphincter.

MATERIALS AND METHODS

In 20 volunteers, studies of gastro-esophageal function were performed on four separate days, following consumption of a standardized meal, with saliva nitrite concentrations modified differently each day by intra-oral nitrite infusion.

RESULTS

The infusions produced an appropriate range in saliva nitrite concentrations, from below to well above the physiological range. The standardized meal induced expected physiological changes in gastro-esophageal function confirming the recordings were sensitive and robust. Esophageal acid exposure (primary outcome) was similar on each study day. Secondary outcomes, including number and duration of reflux events, rate of transient lower esophageal sphincter relaxations, lower esophageal sphincter pressure and rate of gastric emptying were also unaffected by variations in saliva nitrite concentration.

CONCLUSIONS

Nitrite in swallowed saliva does not modify gastro-esophageal junction function or predispose to gastro-esophageal reflux. The wide range in saliva nitrite concentrations, the sensitivity of the physiological recordings and the number of subjects studied make it very unlikely that an effect has been missed.

Perception of dysphagia: lack of correlation with objective measurements of esophageal function

BACKGROUND

The mechanism underlying increased perception of food bolus passage in the absence of esophageal mechanical obstruction has not been completely elucidated. A correlation between the intensity of the symptom and the severity of esophageal dysfunction, either motility (manometry) or bolus transit (impedance) has not been clearly demonstrated. The aim of this study was to analyze the correlation between objective esophageal function assessment (with manometry and impedance) and perception of bolus passage in healthy volunteers (HV) with normal and pharmacologically-induced esophageal hypocontractility, and in patients with gastro-esophageal reflux disease (GERD) with and without ineffective esophageal motility (IEM).

METHODS

Combined manometry-impedance was performed in 10 HV, 19 GERD patients without IEM and nine patients with IEM. Additionally, nine HV were studied after 50 mg sildenafil, which induced esophageal peristaltic failure. Perception of each 5 mL viscous swallow was evaluated using a 5-point scale. Manometry identified hypocontractility (contractions lower than 30 mmHg) and impedance identified incomplete bolus clearance.

KEY RESULTS

In HV and in GERD patients with and without IEM, there was no association between either manometry or impedance and perception on per swallow analysis (OR: 0.842 and OR: 2.017, respectively), as well as on per subject analysis (P = 0.44 and P = 0.16, respectively). Lack of correlation was also found in HV with esophageal hypocontractility induced by sildenafil.

CONCLUSIONS & INFERENCES

There is no agreement between objective measurements of esophageal function and subjective perception of bolus passage. These results suggest that increased bolus passage perception in patients without mechanical obstruction might be due to esophageal hypersensitivity.

Lower esophageal sphincter relaxation reflex kinetics: effects of peristaltic reflexes and maturation in human premature neonates

We defined the sensory-motor characteristics of the lower esophageal sphincter relaxation (LESR) (stimulus threshold volume, response onset, and relaxation period, relaxation magnitude, nadir) during maturation in human neonates. We hypothesized that LESR kinetics differs during maturation and with peristaltic reflex type. Basal and adaptive esophageal motility testing was performed (N = 20 premature neonates) at 34.7 and 39.1 wk (time 1 and time 2). Effects of midesophageal provocation with graded stimuli (N = 1,267 stimuli, air and liquids) on LESR kinetics during esophagodeglutition response (EDR) and secondary peristalsis (SP) were analyzed by mixed models. Frequency of LESR with basal primary peristalsis were different during maturation (P = 0.03). During adaptive responses with maturation, 1) the frequencies of peristaltic reflexes and LESR were similar; 2) liquid stimuli resulted in a shorter LESR response latency and LESR nadir and greater LESR magnitude (all P < 0.05); 3) media differences were noted with LESR response latency (air vs. liquids, P < 0.02); and 4) infusion flow rate-LESR were different (P < 0.01 for air and liquids). Mechanistically, 1) frequency of LESR was greater during peristaltic reflexes at both times (vs. none, P < 0.0001); 2) LESR response latency, duration, and time to complete LESR were longer with EDR (all P < 0.05, vs. SP at time 2); and 3) graded stimulus volume LESR were different for air and liquids (P < 0.01). In conclusion, sensory-motor characteristics of LESR depend on the mechanosensitive properties of the stimulus (media, volume, flow), type of peristaltic reflex, and postnatal maturation. Maturation modulates an increased recruitment of inhibitory pathways that favor LESR.

Noncardiac chest pain-treatment approaches

Treatment of noncardiac chest pain is often difficult because of the heterogeneous nature of the disorder. This condition can stem from gastroesophageal reflux, visceral hyperalgesia, esophageal motility disorders, psychiatric dysfunction, abnormal biomechanical properties of the esophageal wall, sustained esophageal contractions, abnormal cerebral processing of visceral stimulation, or disrupted autonomic activity. For a treatment to be successful, diagnosis of the underlying cause is essential. This article examines three decades of studies from around the world. It concludes that new research into additional mechanisms involved in visceral pain appears promising; but that future studies using improved selective adenosine receptor antagonists and other therapeutic interventions are needed.

Sildenafil relieves symptoms and normalizes motility in patients with oesophageal spasm: a report of two cases

Oesophageal spasm presents with dysphagia and chest pain. Current treatments are limited by poor efficacy and side effects. Studies in health and oesophageal dysmotility show that sildenafil reduces peristaltic pressure and velocity; however the clinical efficacy and tolerability in symptomatic oesophageal spasm remains uncertain. We provided open-label sildenafil treatment to two patients with severe, treatment resistant symptoms associated with oesophageal spasm. The effects of sildenafil on oesophageal function and symptoms were documented by high resolution manometry (HRM). Patients were followed up to assess the efficacy of maintenance treatment with sildenafil b.i.d. HRM revealed focal and diffuse spasm in the smooth muscle oesophagus that were associated with symptoms in both cases, especially on swallowing solids. Lower oesophageal sphincter function was normal. A therapeutic trial of 25-50 mg sildenafil suppressed oesophageal contraction almost completely for water swallows; however effective, coordinated peristalsis returned with reduced frequency of spasm for solid swallows. Dysphagia and chest pain resolved during the therapeutic trial and efficacy was maintained on maintenance treatment with 25-50 mg sildenafil b.i.d. without troublesome side effects. This report shows that sildenafil can improve oesophageal function and relieve dysphagia and chest pain in patients with oesophageal spasm in whom other treatments have failed.

The effect of sildenafil on segmental oesophageal motility and gastro-oesophageal reflux

BACKGROUND

Sildenafil is an inhibitor of type 5 phosphodiesterase. It relaxes or inhibits contraction of smooth muscle by increasing cellular concentrations of cyclic guanosine monophosphate. Multichannel intraluminal impedance manometry/pH allow the precise evaluation of oesophageal bolus transit and acid/non-acid reflux.

AIM

To investigate the effect of sildenafil on segmental oesophageal motor function and gastro-oesophageal reflux.

METHODS

Eight healthy volunteers underwent multichannel intraluminal impedance manometry baseline, and 15, 30 and 45 min before and after a 50-mg dose of sildenafil successively. The subjects underwent 2-h multichannel intraluminal impedance/pH studies on two separate days after either water or sildenafil ingestion.

RESULTS

Sildenafil decreased the resting lower oesophageal sphincter pressure and prolonged the duration of lower oesophageal sphincter relaxation for the 45 min following its ingestion. At 15 min, distal onset velocity, total bolus transit time, bolus presence time and segmental transit time were delayed in the mid to distal oesophagus. At 30 min, distal onset velocity was restored but bolus presence time and bolus presence time were still delayed in distal smooth muscle segment. At 45 min, total bolus transit time and distal onset velocity were restored but bolus presence time and segmental transit time were delayed more in the transition zone. Sildenafil did not alter the reflux.

CONCLUSION

Sildenafil alters lower oesophageal sphincter function and oesophageal bolus transit, but not induce gastro-oesophageal reflux.

Effects of a 5-HT(4) receptor agonist on oesophageal function and gastro-oesophageal reflux: studies using combined impedance-manometry and combined impedance-pH

BACKGROUND

5-HT(4) receptor agonists are used as promotility agents of the stomach, small and large intestine. There is limited information on the influence of 5-HT(4) receptor agonists on oesophageal function and gastro-oesophageal reflux.

AIM

To evaluate the effects of tegaserod, a 5-HT(4) agonist on oesophageal function using impedance-manometry and postprandial reflux using impedance-pH monitoring.

METHODS

Twenty healthy volunteers were enrolled in a double-blind randomized three-period crossover placebo-controlled study. Impedance-manometry and impedance-pH monitoring after a refluxogenic meal were performed at baseline and after 2 days of dosing with tegaserod 6 mg b.d. or placebo. Multichannel intraluminal impedance-EM recorded pressure and bolus transit data during standardized swallows. Multichannel intraluminal impedance-pH monitoring recorded the number of 2-h postprandial acid and non-acid reflux episodes.

RESULTS

We found no significant difference in distal oesophageal amplitude when subjects received placebo (median 94.5; range: 53-243 mmHg) or tegaserod (93.6; 43-216 mmHg). Bolus transit time was similar during dosing with placebo (7.1; 5.3-9.4 s) and tegaserod (7.2; 5.9-11.1 s). We observed similar numbers of acid and non-acid reflux episodes during dosing with placebo (5; 0-15 and 3; 0-18, respectively) and tegaserod (2; 0-11 and 4; 0-19, respectively).

CONCLUSION

Tegaserod, a 5-HT(4) receptor agonist does not change oesophageal motility and gastro-oesophageal reflux parameters in healthy volunteers.

Effect of Sildenafil Citrate on Postprandial Gallbladder Motility

OBJECTIVE

Sildenafil stimulates the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway through inhibition of type 5 phosphodiesterase. NO-cGMP pathway causes smooth muscle relaxation. The aim of this study is to evaluate the effects of sildenafil on gallbladder motility.

METHODS

Twenty healthy male volunteers (21-35 years old) participated in this randomized, double blind, crossover, and placebo-controlled study. Oral sildenafil (50 mg) or placebo was randomly dispensed to each volunteer on two consecutive days. After the sildenafil or placebo, a special meal with a high fat content was administered. Gallbladder volume was measured using sonography preprandially and at 5, 15, 30, 60, 120 and 180 minutes postprandially.

RESULTS

Sildenafil showed an inhibitory effect on gallbladder contraction in healthy volunteers that began at 30 minutes. Gallbladder volumes showed significant differences at 30 minutes following the test meal (approximately 50-60 min after the sildenafil intake), between placebo (15.4 +/- 5.1 mL) and the sildenafil groups (19.3 +/- 6.1 mL) (P < 0.05). In addition, gallbladder volume was significantly higher during the refilling phase in the sildenafil group (P < 0.05 at 180 min). Maximal contraction was achieved at 60 minutes in each group.

CONCLUSIONS

Sildenafil constituted a significant inhibitory effect on gallbladder discharge in healthy individuals when compared with placebo group. Because of this inhibitory effect, sildenafil consumption for long periods may potentiate risks of gallbladder disorders and gallstone formation resulting from disturbed gallbladder motility.

Gastrointestinal Function Regulation by Nitrergic Efferent Nerves

Gastrointestinal (GI) smooth muscle responses to stimulation of the nonadrenergic noncholinergic inhibitory nerves have been suggested to be mediated by polypeptides, ATP, or another unidentified neurotransmitter. The discovery of nitric-oxide (NO) synthase inhibitors greatly contributed to our understanding of mechanisms involved in these responses, leading to the novel hypothesis that NO, an inorganic, gaseous molecule, acts as an inhibitory neurotransmitter. The nerves whose transmitter function depends on the NO release are called "nitrergic", and such nerves are recognized to play major roles in the control of smooth muscle tone and motility and of fluid secretion in the GI tract. Endothelium-derived relaxing factor, discovered by Furchgott and Zawadzki, has been identified to be NO that is biosynthesized from l-arginine by the constitutive NO synthase in endothelial cells and neurons. NO as a mediator or transmitter activates soluble guanylyl cyclase and produces cyclic GMP in smooth muscle cells, resulting in relaxation of the vasculature. On the other hand, NO-induced GI smooth muscle relaxation is mediated, not only by cyclic GMP directly or indirectly via hyperpolarization, but also by cyclic GMP-independent mechanisms. Numerous cotransmitters and cross talk of autonomic efferent nerves make the neural control of GI functions complicated. However, the findingsrelated to the nitrergic innervation may provide us a new way of understanding GI tract physiology and pathophysiology and might result in the development of new therapies of GI diseases. This review article covers the discovery of nitrergic nerves, their functional roles, and pathological implications in the GI tract.

Inhibitory effects of sildenafil citrate on the tonus of isolated dog internal anal sphincter

PURPOSE

Although the exact pathogenesis of anal fissure is not known, hypertonicity of the internal anal sphincter might be involved in its pathogenesis as main event. To gain information about possible usefulness of the novel, smooth-muscle-relaxing drug, sildenafil, in chronic anal fissure, we investigated the effect of sildenafil citrate on acetylcholine-induced contractility of internal anal sphincter isolated from dogs.

METHODS

Internal anal sphincter strips were taken from German shepherd dogs and suspended in a tissue bath filled with Krebs solution at 37 degrees C (pH 7.4) continuously bubbled with 95 percent oxygen and 5 percent carbon dioxide, and isometric contractions were recorded. Contractions were evoked by 10 muM acetylcholine, and the effects of different concentrations of sildenafil citrate (0.1, 0.3, and 1 mM) on the isometric tension of each internal anal sphincter strip were examined. The statistical significance was analyzed by one-way analysis of variance.

RESULTS

Pretreatment with sildenafil citrate (0.1 mM) attenuated contractile response to acetylcholine (n = 3), which were significantly weak compared with the maximum contractile response to the acetylcholine alone (610 +/- 110 mg vs. 2,825.17 +/- 416 mg; n = 12; P < 0.05). Sildenafil citrate also significantly inhibited the acetylcholine-induced contractions in a dose-dependent manner when applied after.

CONCLUSIONS

This experimental in vitro study showed that sildenafil citrate relaxes acetylcholine stimulated contractions of isolated dog internal anal sphincter. This may be of importance for raising the possibility that sildenafil cit-rate may have future potential in the treatment of chronic anal fissure. Further studies are needed for a conclusive decision on possible usefulness of sildenafil citrate in patients with chronic anal fissure.

A pilot study of the effects of sildenafil on stool characteristics, colon transit, anal sphincter function, and rectal sensation in healthy men

Nitric oxide is an important mediator of gut smooth muscle relaxation and visceral sensation. Sildenafil results in stimulation of the nitric oxide-cyclic GMP pathway. We sought to determine the effects of daily sildenafil administration on colorectal function. Over a 4-week period, sildenafil was administered during weeks 2 and 3. Stool frequency and consistency were assessed daily. Anorectal manometry, rectal sensation, and colon transit testing were performed at the end of weeks 1 and 3. Ten healthy men were studied. No significant differences in segmental or total colon transit time were noted; however, significant changes in stool frequency and trends toward decreased stool consistency were noted during sildenafil use. A trend toward reduced resting anal sphincter pressure was seen after sildenafil. Rectal volumes to first sensation and desire to defecate were significantly increased after sildenafil on test day 2 only. Additionally, volumes to desire to defecate and maximal tolerable volume were significantly increased before sildenafil on test day 2 compared to before sildenafil on test day 1. We conclude that daily administration of sildenafil is well tolerated and results in alterations in colorectal function.

Ineffective esophageal motility in gastroesophageal erosive reflux disease and in nonerosive reflux disease: are they different?

BACKGROUND

In GERD patients, ineffective esophageal motility (IEM), a hypocontractile disorder, is the most common motor abnormality. IEM has been associated with reflux in both the supine and upright position, prolonged esophageal clearance, and delayed of bolus transport. IEM has been equally present in erosive and in nonerosive GERD.

GOAL

Considering that reflux has been found to be more severe in erosive GERD than in nonerosive GERD patients and that IEM delays esophageal clearance, our hypothesis is that patients with erosive GERD have more severe IEM than those with nonerosive disease.

STUDY

A retrospective review of consecutive manometries of patients with the chief complaint of heartburn and a diagnosis of IEM were performed, and patients with both erosive and nonerosive GERD were selected. According to the number of ineffective contractions, IEM was stratified into three groups: 30% to 40%, mild; 50% to 60%, moderate; and greater than 60%, severe. We also registered the number of low amplitude, failed, and normal waves in each manometry of both groups. We evaluated 110 patients: 70 (64%) with erosive GERD and 40 (36%) with nonerosive GERD. The percentage of mild, moderate and severe IEM was similar in erosive and in nonerosive GERD patients, as well the number of low amplitude, failed or normal waves (P < 0.5).

CONCLUSION

There were no differences between the severity of IEM in erosive and in nonerosive GERD patients.

Effect of sildenafil on gastric emptying and postprandial frequency of antral contractions in healthy humans

BACKGROUND

Sildenafil is known to block phosphodiesterase type 5, which degrades nitric oxide-stimulated cyclic guanosine monophosphate, thereby relaxing smooth muscle cells in various organs. The effect of sildenafil on gastric motor function after a meal was investigated in healthy humans.

METHODS

Ten healthy male volunteers (21-28 years) participated in a placebo-controlled, double-blind, cross-over study. In random order and on two separate days each volunteer ingested either 50 mg sildenafil (Viagra, Pfizer, New York, N.Y., USA) or placebo. A gamma camera technique was used to measure gastric emptying and postprandial frequency of antral contractions.

RESULTS

The area under the curve of gastric retention versus time of liquid or solid radiolabelled marker was not changed by sildenafil intake, nor was the postprandial frequency of antral contractions affected by sildenafil.

CONCLUSION

A single dose of 50 mg sildenafil does not change gastric emptying or postprandial frequency of antral contractions in healthy volunteers.

The effect of sildenafil on oesophageal motor function in healthy subjects and patients with nutcracker oesophagus

Type 5 phosphodiesterase terminates the action of nitric oxide (NO) induced 3',5'-cyclic monophosphate (cGMP). Sildenafil inhibits this phosphodiesterase, increases cellular cGMP concentrations and enhances NO-induced smooth muscle relaxation. We investigated the effect of sildenafil on the oesophageal motor function of healthy subjects and patients with nutcracker oesophagus. Eight healthy volunteers and nine patients with nutcracker oesophagus participated in this study. The participants underwent oesophageal manometries on two separate days after either 20 mL of distilled water or 0.8 mg kg-1 sildenafil dissolved in 20 mL of water was infused into the stomach. Lower oesophageal sphincter (LOS) resting pressure, the duration of LOS relaxation and the amplitudes of oesophageal pressure waves were examined before, and 7.5, 15, 30 and 60 min after either placebo or sildenafil. In both healthy subjects and patients with nutcracker oesophagus, sildenafil decreased resting LOS pressure and the amplitude of peristaltic pressure waves at 3, 8 and 13 cm above LOS. Sildenafil also prolonged the duration of LOS relaxation. It had no effect on the velocity of peristalsis or the amplitude of peristaltic pressure waves 18 cm above LOS. Sildenafil may be considered as an alternative treatment in nutcracker oesophagus although there are several limitations to be overcome.

Effects of phosphodiesterase inhibitors on oesophageal neuromuscular functions

The cyclic nucleotides adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) mediate the inhibitory effects of vasoactive intestinal polypeptide and nitric oxide on oesophageal smooth muscle. Phosphodiesterases (PDE) terminate their actions. We hypothesized that PDE inhibitors alter nerve-induced responses of oesophageal and lower oesophageal sphincter (LES) smooth muscle. An electrical field known to activate intrinsic oesophageal nerves was used to stimulate transverse muscle strips from the opossum oesophagus. This produced a contractile off-response from circular oesophageal muscle and a biphasic relaxation of the LES - an initial rapid relaxation (R1) and a slower sustained relaxation (R2). The effects on LES and oesophageal muscle of zaprinast (type V), zardaverine (type III/IV) and theophylline (non-specific) PDE inhibitors were explored. All three PDE inhibitors decreased LES tone and attenuated the off-response. Zaprinast and theophylline increased the latency of the off-response. Zaprinast prolonged R1, and slowed its recovery. It also increased the percentage relaxation of the second R2. Zardaverine increased the percentage relaxation of R2. Theophylline slowed the recovery of R2. PDEs play a role in maintaining LES tone and its recovery after LES relaxation. They may also modulate oesophageal motor activity.

Medication-induced oesophageal disorders

Medication-induced oesophageal distress and injury have become increasingly common conditions. First, smooth muscle relaxants may worsen or produce symptoms of pre-existing gastro-oesophageal reflux disease; notable examples include certain calcium antagonists (nifedipine), nitrates, sildenafil, nicotine, theophylline, and substances with antimuscarinic potential. Second, drugs with local toxicity may produce de novo damage including inflammation, strictures, ulcers, and bleeding. Notorious examples are alendronate, certain antibiotics including tetracyclines and clindamycin, all NSAIDs/aspirin, quinidine, potassium chloride, and ferrous sulfate. Cyclooxygenase-2 inhibitors may be devoid of such toxicity, but may damage the mucosa by interfering with regenerative cell proliferation. The galenic formulation can modulate the risk of oesophageal injury. For this reason, medicines containing the same potentially toxic ingredient may be less exchangeable than commonly thought. Diagnostic gold standard is endoscopy. The best treatment is removal of the offending drug and supportive care. Prevention requires a re-appraisal of the drug's indication and adherence to guidelines of optimal drug intake including ingestion in an upright position and swallowing with enough fluid. The clinical relevance of drug-induced oesophageal injury and the feasibility of therapeutic alternatives are individually addressed.