Model systems for the evaluation of mucolytic drugs: acetylcysteine and S-carboxymethylcysteine

N-Acetylcysteine: A Review of Clinical Usefulness (an Old Drug with New Tricks)

OBJECTIVE

To review the clinical usefulness of N-acetylcysteine (NAC) as treatment or adjunctive therapy in a number of medical conditions. Use in Tylenol overdose, cystic fibrosis, and chronic obstructive lung disease has been well documented, but there is emerging evidence many other conditions would benefit from this safe, simple, and inexpensive intervention. Quality of Evidence. PubMed, several books, and conference proceedings were searched for articles on NAC and health conditions listed above reviewing supportive evidence. This study uses a traditional integrated review format, and clinically relevant information is assessed using the American Family Physician Evidence-Based Medicine Toolkit. A table summarizing the potential mechanisms of action for N-acetylcysteine in these conditions is presented. Main Message. N-acetylcysteine may be useful as an adjuvant in treating various medical conditions, especially chronic diseases. These conditions include polycystic ovary disease, male infertility, sleep apnea, acquired immune deficiency syndrome, influenza, parkinsonism, multiple sclerosis, peripheral neuropathy, stroke outcomes, diabetic neuropathy, Crohn's disease, ulcerative colitis, schizophrenia, bipolar illness, and obsessive compulsive disorder; it can also be useful as a chelator for heavy metals and nanoparticles. There are also a number of other conditions that may show benefit; however, the evidence is not as robust.

CONCLUSION

The use of N-acetylcysteine should be considered in a number of conditions as our population ages and levels of glutathione drop. Supplementation may contribute to reducing morbidity and mortality in some chronic conditions as outlined in the article.

S-Carboxymethyl-l-cysteine: a multiple dosing study using pharmacokinetic modelling

S-Carboxymethyl-l-cysteine is a mucolytic agent used as adjunctive therapy in the treatment of respiratory disorders. Various mechanisms of action have been proposed but few studies have attempted to link the required in vitro concentrations with those achieved actually in vivo during clinical therapy.The data from several published studies has been re-analysed by WinNonlin using non-compartmental analysis modelling, Phoenix modelling and Classic PK compartmental modelling for both single (500-1500 mg) and multiple oral administration of the drug.Multiple dose modelling indicated maximum peak concentrations (C_max) ranging from 1.29 to 11.22 μg/ml and those at steady state (C_ss(av)) from 1.30 to 8.40 μg/ml. For the standard therapeutic regimen of 3 × 750 mg (2250 mg/day) these values were 1.29-5.22 μg/ml (C_max) and 1.30-3.50 μg/ml (C_ss(av)). No accumulation was observed.Hence, only the pharmacodynamic studies reporting significant effects below c.10 μg/ml were likely to occur in vivo and these were mainly gene-related mechanisms. The majority of events, although demonstrable in vitro, required levels much greater than possible to achieve in the clinical situation.Such unappreciated disregard for in vitro-in vivo 'concentration matching' may lead to erroneous conclusions regarding mechanisms of action for many drugs as well as for S-carboxymethyl-l-cysteine.

Scientific Papers and Patents on Substances with Unproven Effects. Part 2

Several examples are discussed in this review, where substances without proven effects were proposed for practical use within the scope of evidence-based medicines. The following is discussed here: generalizations of the hormesis concept and its use in support of homeopathy; phytoestrogens and soy products potentially having feminizing effects; glycosaminoglycans for the treatment of osteoarthritis and possibilities of their replacement by diet modifications; flavonoids recommended for the treatment of chronic venous insufficiency and varicose veins; acetylcysteine as a mucolytic agent and its questionable efficiency especially by an oral intake; stem cells and cell therapies. In conclusion, placebo therapies can be beneficial and ethically justifiable but it is not a sufficient reason to publish biased information. Importantly, placebo must be devoid of adverse effects, otherwise, it is named pseudo-placebo. Therapeutic methods with unproven effects should be tested in high-quality research shielded from the funding bias. Some issues discussed in this review are not entirely clear, and the arguments provided here can initiate a constructive discussion.

Synthesis and characterization of potential stereoisomeric and degradation impurities of ulipristal acetate

Potential stereoisomeric and degradation impurities of UPA has been synthesized through practical approaches which would be valuable for the quality control of UPA.

Erdosteine: Drug exhibiting polypharmacy for the treatment of respiratory diseases

Mucoactive drugs are commonly used in the treatment of acute respiratory tract diseases, such as lower and acute respiratory infection and chronic bronchitis (CB) or chronic obstructive pulmonary disease (COPD) in which an increased mucus secretion is one of main clinical features. Indeed these drugs are designed to promote secretion clearance and to specifically alter the viscoelastic properties of mucus, restoring an effective mucociliary clearance and reducing broncho-obstructive symptoms. In association with mucolytics, these patients frequently also receive antibiotics to reduce the bacterial load, thus decreasing the release of infectious and pro-inflammatory products. Erdosteine is one of the most used mucoactive agents for the treatment of several respiratory diseases where the overlap of bacterial infection is frequent. Although the effectiveness in the reducing mucus in acute and chronic respiratory disease has been demonstrated for others mucolytic, some of them when given in combination with an antibiotic therapy, could reduce the antibiotic efficacy in some situation. Differently, erdosteine potentiates the antibiotic effect when given in combination with antibiotics. We have reviewed the literature available on both clinical and in vitro studies that have investigated this effect of erdosteine on the effect of antibiotics when used as combined therapy.

Effectiveness of N-acetyl cysteine, 2% chlorhexidine, and their combination as intracanal medicaments on Enterococcus faecalis biofilm

Aim:

The purpose of this study was to evaluate the antibacterial efficacies of 2% chlorhexidine (CHX), N-acetyl cysteine (NAC) and assess their synergistic or antagonist action as intracanal medicament.

Materials and Methods:

Agar diffusion test was performed with 2% CHX, NAC, and their combination against E. faecalis planktonic cells. The diameters of the zones of bacterial inhibition were measured and recorded for each solution. The assay was further extended to 2 weeks old E. faecalis dentinal biofilm. Sixteen freshly extracted teeth were vertically sectioned into two halves resulting in a total of 32 samples. The samples were inoculated with bacterial suspension and incubated at 37°C for 2 weeks for biofilm formation. The samples were then divided into four experimental groups with 8 samples in each group. The samples were gently washed in saline and placed in culture wells containing the test solutions, i.e., 2% CHX, NAC, a combination of 2% CHX and NAC in 1:1 ratio, and a control group containing saline. The biofilm formed on the root canal surface were removed with a sterile scalpel and inoculated on blood agar plates to check for the formation of E. faecalis colonies.

Statistical Analysis:

For agar diffusion test, data were analyzed statistically using one-way analysis of variance and then by post-hoc Scheffe's test to compare the antimicrobial efficacy between the groups. Statistical analysis was not done for the cultures obtained from the biofilm as there was no growth in all the three test groups except the control group, i.e., saline.

Results:

In agar diffusion test, among the three groups tested, 2% CHX and NAC showed almost equal zones of inhibition whereas maximum inhibition was shown by a combination of NAC and 2% CHX suggesting a synergistic action. The results obtained were highly significant (P < 0.001) for the combination of medicament when compared to individual test group. In culture analysis, which was done for the biofilm, no growth was observed in all the three test groups. The results obtained were biologically significant but statistically insignificant.

Conclusion:

NAC has almost equal antimicrobial property as 2% CHX whereas their combination showed a synergistic action.

Absorption enhancement of poorly absorbed hydrophilic compounds from various mucosal sites by combination of mucolytic agent and non-ionic surfactant

Absorption enhancement of poorly absorbed hydrophilic compounds from various mucosal sites by co-administration of a mucolytic agent and a non-ionic surfactant was examined in rats. Fluorescein isothiocyanate-labeled dextran with average molecular weight of ca. 4.4kDa (FD-4), and salmon calcitonin (SCT) were used as model compounds. N-acetylcysteine (NAC) and p-t-octyl phenol polyoxyethylene-9.5 (Triton X-100, TX-100) were selected as a mucolytic agent and a non-ionic surfactant, respectively. Dosing solutions containing these agents were administered into various mucosal sites including the nose, the lung and the large intestine, and the bioavailabilities were determined. The combination of 5% NAC and 5% TX-100 significantly enhanced the nasal, the pulmonary and the large intestinal absorption of FD-4 compared to the control, and the enhancement ratios relative to the control were 7.2-, 2.8- and 4.5-fold, respectively. The different enhancement ratio among the administration sites explored indicates that the absorption enhancing effect of the combination of NAC and TX-100 is site-dependent. This combination also improved the nasal and the pulmonary absorption of SCT, and the enhancement ratios relative to the control were 6.1- and 8.1-fold, respectively. All these results suggest that the combination strategy of a mucolytic agent and a non-ionic surfactant may be widely applicable to various mucosal deliveries of poorly absorbed hydrophilic compounds.

Role of N-acetylcysteine in the management of COPD

The importance of the underlying local and systemic oxidative stress and inflammation in chronic obstructive pulmonary disease (COPD) has long been established. In view of the lack of therapy that might inhibit the progress of the disease, there is an urgent need for a successful therapeutic approach that, through affecting the pathological processes, will influence the subsequent issues in COPD management such as lung function, airway clearance, dyspnoea, exacerbation, and quality of life. N-acetylcysteine (NAC) is a mucolytic and antioxidant drug that may also influence several inflammatory pathways. It provides the sulfhydryl groups and acts both as a precursor of reduced glutathione and as a direct reactive oxygen species (ROS) scavenger, hence regulating the redox status in the cells. The changed redox status may, in turn, influence the inflammation-controlling pathways. Moreover, as a mucolytic drug, it may, by means of decreasing viscosity of the sputum, clean the bronchi leading to a decrease in dyspnoea and improved lung function. Nevertheless, as successful as it is in the in vitro studies and in vivo studies with high dosage, its actions at the dosages used in COPD management are debatable. It seems to influence exacerbation rate and limit the number of hospitalization days, however, with little or no influence on the lung function parameters. Despite these considerations and in view of the present lack of effective therapies to inhibit disease progression in COPD, NAC and its derivatives with their multiple molecular modes of action remain promising medication once doses and route of administration are optimized.

The role of Mucodyne in reducing the need for surgery in patients with persistent otitis media with effusion

A recent meta-analysis suggested a possible beneficial effect of carboxymethylcysteine (Mucodyne) in resolving otitis media with effusion (OME), but the methodology in several of the included trials was flawed. A double-blind randomised controlled trial (RCT) involving 163 patients (78 randomised to Mucodyne and 85 to placebo) was therefore performed.

MAIN OUTCOME MEASURE

operative intervention or not. Of the 28 patients with resolved OME, 17 were in the Mucodyne group and 11 in the placebo group. Although it appeared that patients treated with Mucodyne were 1.68 times more likely to undergo resolution of OME than patients receiving placebo, this did not reach statistical significance. [Risk ratio of 1.68 (95% C.I., 0.74-3.37)]. chi2 test (df = 162) = 2.24 (P = 0.134). The absolute risk difference in the study was 8.5% (95% C.I., -3-20). We cannot exclude the possibility that Mucodyne is as beneficial as a 20% additional resolution of OME, or as harmful as a 3% decrease in the resolution of OME.

The physical properties of biogels and their permeability for macromolecular drugs and colloidal drug carriers

Macromolecular drugs, either free or complexed with colloidal drug carriers, have created a great deal of interest during the last decade. If one wants to administer these new therapeutics via the oral, nasal, and cervical routes or through the conductive airways, one of the first barriers to overcome is the mucus layer that adheres to the related epithelia. In this review, the physicochemical properties of biogels, macromolecular drugs, and colloidal drug carriers that play a major role in transport through biogels are reviewed. Also, methods of studying the mobility of macromolecular drugs and colloidal drug carriers in and through biogels are addressed.

Mucolytic and antitussive effects of erdosteine

To investigate the influence of erdosteine, a new homocysteine-derived expectorant, on airway clearance we studied the effects of the drug on the viscosity of mucin, on the mucociliary transport rate in quails, on airway secretion in rats and on the cough reflex in guinea-pigs. The active metabolite of erdosteine, M1 (10 microM to 1 mM), significantly reduced the viscosity of porcine stomach mucin. Erdosteine by itself did not reduce viscosity. Erdosteine significantly promoted mucociliary transport in quails and increased airway secretion in rats. The effect was still apparent 24h after administration. Erdosteine significantly suppressed citric acid-induced cough reflexes in guinea-pigs but did not suppress mechanical stimuli-induced cough reflexes. Erdosteine suppressed the reduction of the recovery volume of bronchoalveolar lavage fluid and albumin leakage into the fluid in citric acid-exposed guinea-pigs. These results indicate that erdosteine removes sputum by reducing its viscosity, and by promoting mucociliary transport and sustained enhancement of airway secretion. It also suppressed the chemical stimulation-induced cough reflex and plasma leakage into the airway. These results suggest that erdosteine is an excellent expectorant with several modes of action.