Acid inhibition and the acid rebound effect

Is empirical treatment a reasonable strategy for laryngopharyngeal reflux? A contemporary review

BACKGROUND

Diagnosis and treatment of presumed laryngopharyngeal reflux (LPR) remain controversial. Empiric medication trials remain widespread for suspected LPR despite emerging evidence against proton pump inhibitor (PPI) safety and for pepsin as a mediator of LPR symptoms. Ongoing concerns exist related to inaccurate diagnosis, the cost and morbidity of potentially unnecessary PPI prescriptions, and availability and interpretation of objective reflux testing.

OBJECTIVES

To review contemporary evidence that does and does not support empiric medication trials for presumed LPR.

METHODS

PubMed, Scopus and Cochrane Library were searched for literature about benefits, limitations and alternatives to empiric medication trial for LPR, in order to present both sides of this debate and identify best practices.

RESULTS

The majority of physicians perform prolonged empiric medication trial with PPIs for patients with suspected LPR. Because symptoms and signs of LPR are non-specific, empiric medication trials require exclusion of other conditions that can mimic LPR. Following a PPI empiric medication trial, over one-third of patients remain non-responders. The use of hypopharyngeal-oesophageal multichannel intraluminal impedance-pH monitoring (HEMII-pH) has benefits and limitations in objective diagnosis of LPR.

CONCLUSIONS

Use of PPIs for single-agent empiric medication trial does not account for possible non-responders with non-acid or mixed LPR. If LPR diagnosis remains uncertain, alginates can be added to PPI trials. HEMII-pH testing upfront is ideal for patients with suspected LPR, but not always practical; it is indicated when PPI and alginate empiric medication trials have failed or when comorbidities confuse the diagnosis. A more comprehensive, combination therapy empiric medication trial regimen may be needed.

Modulations in extracellular calcium lead to H+-ATPase-dependent acid secretion: a clarification of PPI failure

The H+,K+-ATPase was identified as the primary proton secretory pathway in the gastric parietal cell and is the pharmacological target of agents suppressing acid secretion. Recently, we identified a second acid secretory protein expressed in the parietal cell, the vacuolar H+-ATPase (V-type ATPase). The aim of the present study was to further characterize H+-ATPase activation by modulations in extracellular calcium via the calcium sensing receptor (CaSR). Isolated gastric glands were loaded with the pH indicator dye BCECF-AM [2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester] to measure intracellular pH. Experiments were conducted in the absence of sodium and potassium to monitor H+-ATPase-specific transport activity. CaSR was activated with the calcimimetic R568 (400 nM) and/or by modulations in extracellular Ca2+. Elevation in calcium concentrations increased proton extrusion from the gastric parietal cell. Allosteric modification of the CaSR via R568 and calcium increased vacuolar H+-ATPase activity significantly (ΔpH/minlowCa2+(0.1mM) = 0.001 ± 0.001, ΔpH/minnormalCa2+(1.0mM) = 0.033 ± 0.004, ΔpH/minhighCa2+(5.0mM) = 0.051 ± 0.005). Carbachol significantly suppressed calcium-induced gastric acid secretion via the H+-ATPase under sodium- and potassium-free conditions. We conclude that the V-type H+-ATPase is tightly linked to CaSR activation. We observed that proton pump inhibitor (PPI) exposure does not modulate H+-ATPase activity. This elevated blood calcium activation of the H+-ATPase could provide an explanation for recurrent reflux symptoms while taking a PPI therapy. NEW & NOTEWORTHY This study emphasizes the role of the H+-ATPase in acid secretion. We further demonstrate the modification of this proton excretion pathway by extracellular calcium and the activation of the calcium sensing receptor CaSR. The novelty of this paper is based on the modulation of the H+-ATPase via both extracellular Ca (activation) and the classical secretagogues histamine and carbachol (inactivation). Both activation and inactivation of this proton pump are independent of PPI modulation.

Efficacy and safety of honey based formulation of Nigella sativa seed oil in functional dyspepsia: A double blind randomized controlled clinical trial

ETHNOPHARMACOLOGICAL RELEVANCE

A honey based formulation from Nigella sativa L. (N. sativa) has been used in Traditional Persian Medicine for upper gastrointestinal symptoms. Considering the traditional use of this formulation and its ingredients known pharmacologic effects, this study aimed to evaluate the efficacy and safety of N. sativa seed oil mixed with honey in treatment of patients with functional dyspepsia.

METHODS AND MATERIALS

Seventy patients diagnosed with functional dyspepsia according to ROME III criteria and confirmed by upper gastrointestinal endoscopy were selected to receive a traditional honey based formulation of N. sativa (5 ml N. sativa oil orally daily) or placebo for 8 weeks in a double-blind randomized placebo-controlled clinical trial using a parallel design with a 1:1 allocation ratio. Patients were evaluated prior to and following 8 weeks of the intervention in terms of the Hong Kong index of dyspepsia severity, presence of Helicobacter pylori infection based on urease test, scores in different domains of short form (SF-36) health survey, and any observed adverse events.

RESULTS

The mean scores of Hong Kong index of dyspepsia severity sores and the rate of H. pylori infection were significantly lower in the N. sativa group comparing the placebo group after the intervention (P<0.001). No serious adverse event was reported.

CONCLUSION

This study showed that adjuvant supplementation of honey based formulation of N. sativa can cause significant symptomatic improvement of patients with functional dyspepsia whom received the standard anti-secretory therapy. The results should be investigated further in studies with longer duration and larger sample size.

Role of gastric acid inhibition, prostaglandins and endogenous-free thiol groups on the gastroprotective effect of a proteolytic fraction from Vasconcellea cundinamarcensis latex

OBJECTIVES

The aim of this study was to extend our knowledge about the mechanism involved in the gastroprotective effect of P1G10, a proteolytic fraction rich in cysteine proteinases from Vasconcellea cundinamarcensis (syn. Carica candamarcensis) latex, which demonstrated gastric healing and protection activities in rats.

METHODS

Wistar rats were submitted to gastric lesions by indomethacin and treated with P1G10 (10 mg/kg). Free thiol groups and prostaglandin E2 content were measured in gastric mucosal and gastrin levels in blood samples. To evaluate the participation of nitric oxide (NO) or proteolytic activity of P1G10 on its gastroprotective effect, animals were treated with an inhibitor of NO production (L-NAME) or the fraction inhibited by iodoacetamide, respectively. Gastric secretion study (acidity and pepsin activity) was also performed.

KEY FINDINGS

P1G10 (10 mg/kg) inhibited the occurrence of gastric lesions by indomethacin, restored the free thiol groups content on gastric mucosa and increased moderately prostaglandin E2 levels (34%). Furthermore, the treatment decreased the gastrin levels (95%), suggesting a possible modulation of secretory activity. This effect was accordant with attenuation of gastric acidity (42%) and pepsin activity (69%) seen in animals subjected to pyloric ligation. The inhibition of NO production or the proteolytic activity of P1G10 does not affect the gastroprotective effect.

CONCLUSIONS

These results can explain the gastroprotective activity of P1G10 and serve a basis for further studies of this active principle.

Rebound effect of modern drugs: serious adverse event unknown by health professionals

OBJECTIVE

Supported in the Hippocratic aphorism primum non nocere, the bioethical principle of non-maleficence pray that the medical act cause the least damage or injury to the health of the patient, leaving it to the doctor to assess the risks of a particular therapy through knowledge of possible adverse events of drugs. Among these, the rebound effect represents a common side effect to numerous classes of modern drugs, may cause serious and fatal disorders in patients. This review aims to clarify the health professionals on clinical and epidemiological aspects of rebound phenomenon.

METHODS

A qualitative, exploratory and bibliographic review was held in the PubMed database using the keywords 'rebound', 'withdrawal', 'paradoxical', 'acetylsalicylic acid', 'anti-inflammatory', 'bronchodilator', 'antidepressant', 'statin', 'proton pump inhibitor' and 'bisphosphonate'.

RESULTS

The rebound effect occurs after discontinuation of numerous classes of drugs that act contrary to the disease disorders, exacerbating them at levels above those prior to treatment. Regardless of the disease, the drug and duration of treatment, the phenomenon manifests itself in a small proportion of susceptible individuals. However, it may cause serious and fatal adverse events should be considered a public health problem in view of the enormous consumption of drugs by population.

CONCLUSION

Bringing together a growing and unquestionable body of evidence, the physician needs to have knowledge of the consequences of the rebound effect and how to minimize it, increasing safety in the management of modern drugs. On the other hand, this rebound can be used in a curative way, broadening the spectrum of the modern therapeutics.

A double-blind placebo-controlled randomized trial on probiotics in small bowel bacterial overgrowth in children treated with omeprazole

OBJECTIVE

To evaluate the incidence of small bowel bacterial overgrowth (SBBO) in children treated with omeprazole, and to test whether probiotics influence the incidence.

METHODS

A double-blinded, placebo-controlled trial was performed in 70 children treated orally during four weeks with 20mg omeprazole per day. Lactobacillus rhamnosus R0011 (1.9×10(9) cfu) and Lactobacillus acidophilus R0052 (0.1×10(9) cfu) were simultaneously given daily to 36 subjects (probiotic group), while 34 subjects received placebo (placebo group). The diagnosis of SBBO was based on the development of suggestive symptoms, in combination with a positive glucose breath test.

RESULTS

After one month of proton pump inhibitor (PPI) treatment, 30% (21/70) had a positive breath test suggesting SBBO; of these 62% were symptomatic. Five children developed SBBO-like symptoms, but had a negative breath test; and 44 (63%) were symptom free and had a negative breath test. There was no difference in the incidence of positive breath tests in the probiotic versus the placebo group (33% vs 26.5%; p=0.13).

CONCLUSIONS

Since symptoms suggesting SBBO developed in 26% of PPI-treated children, and since the glucose breath test was abnormal in 72% of these, this side-effect should be more frequently considered. The probiotic tested did not decrease the risk to develop SBBO.