Studies on the reduction of sputum viscosity in cystic fibrosis using an orally absorbed protected thiol

The viscosity of cystic fibrosis fluids leads to clinical difficulties in adequate clearance of the respiratory and gastrointestinal tracts and in delivery of gases and nutrients to their respective sites. Various sulfhydryl agents are effective in reducing in vitro sputum viscosity. Present therapy for cystic fibrosis involves the aerosolization of N-acetylcysteine, presenting problems of toxicity and inadequate delivery to the small airways. We have been assessing various prodrugs which would liberate the free thiol in vivo and which would be orally absorbed. The free thiol of WR 2721, at a concentration of 1 mM, reduces sputum viscosity by 70% in 15 min. WR 2721 is hydrolyzed to the free thiol chemically at an acid pH and enzymatically by homogenates of the liver and gut. It is well absorbed (23%) after oral administration to rabbits. Clinical studies indicate that orally administered WR 2721 is without toxicity and reduces sputum viscosity in cystic fibrosis patients in 30 to 60 min after administration.

The effect of sodium 2-mercapto-ethane sulphonate and hypertonic saline aerosols on bronchial clearance in chronic bronchitis

1 The efficacy of a mucolytic agent, 2-mercapto-ethane sulphonate, administered in the form of an aerosol was evaluated in a group of eleven patients with chronic bronchitis in a controlled, double-blind, crossover study. 2 Saline aerosol isotonic (1.21M, 7.1%) to the drug was used as a placebo. 3 Approximately 1 ml drug/placebo was inhaled by the patients twice a day for 3 days and a final dose was given on the mornings of the drug/placebo trial runs. 4 There was no improvement in this group of patients in lung function or subjective well being attributable to the drug. 5 The viscosity of sputum, dry macromolecular weight and N-acetyl neuraminic acid/fucose ratio remained unaltered throughout the study. 6 An enhancement of tracheobronchial clearance was obtained following the administration of either placebo (31%) or drug aerosols (24%) Statistical significance (P less than 0.01) was only achieved for the placebo and was attributed to an increase in sputum volume.

Use of a mucolytic agent (Cytoclair) in the preparation of cell material for the detection of malignant cells in sputum

A mucolytic agent, methyl cysteine HC1 (Cytoclair), has been used to obtain a centrifuged cell deposit for the detection of malignant cells in sputum. In 178 sputum samples from 52 patients with primary lung cancer there was a slightly higher rate of detection with the mucolytic method than with the routine method: 54 positives from 27 patients compared with 48 positives from 24 patients. Morphological studies using the mucolytic agent indicated that a millipore filter with fixation of cells in suspension produces a satisfactory cell preparation and is valuable in certain problem cases.

Effect of thiol derivatives on mixed mucus and blood clots in vitro

The disintegrating effect of three reducing thiol derivatives: [sodium mercaptoethane sulphonate (Mesna), N-acetyl-L-cysteine (NAC) and dithio-1,4-threitol (DTT)] was investigated in vitro upon blood clots formed in the absence or in the presence of tracheobronchial secretions and compared with the effect of iso-osmotic saline solution. The amounts of haemoglobin released from the clots after 30 min incubation and the initial rates of haemoglobin release were compared for the different products at different concentrations. All three reducing agents showed some ability to disintegrate mixed clots to an extent depending on their concentration. After 30 min incubation, statistical analysis showed a highly significant difference in favour of Mesna at the three concentrations used, i.e. 0.1, 1.0 and 10 mmol/1. The initial rate of haemoglobin release in presence of Mesna was at all concentrations significantly higher than that of NAC or DTT. The effects on normal blood clots were much less pronounced. The effectiveness of Mesna in splitting up mixed blood and mucus clots in the management of patients who had inhaled blood is discussed.

Human cervical mucus. III. Isolation and characterization of rheologically active mucin

Several common mucolytic agents were screened for their ability to solubilize cervical mucus without incurring irreversible losses in mucus viscoelasticity. Sodium thiocyanate was selected on the basis of its effectiveness and handling convenience, and solubilized mucus was fractionated by gel filtration on Sepharose columns. The excluded mucin fraction was characterized by a high neutral hexose to protein ratio and contained all of the elasticity of thiocyanate-treated whole mucus. The concentration of mucin in individual mucus samples collected throughout the ovulatory menstrual cycle was determined from column elution profiles. An increased relative amount of mucin was associated with samples collected during the ovulatory phase of the cycle, and a strong correlation was obtained when the percentage of mucin in individual samples was plotted against their respective storage moduli. These results indicate that the cyclic fluctuations in mucus viscoelasticity seen previously at constant concentrations of nondialyzable solids can be attributed to variations in mucin concentration. Evidence was also obtained, however, for compositional differences in mucus derived from different patients.

Effect of mucolytic agents on the rheological properties of tracheal mucus

Canine tracheal mucus was dissolved by a number of mucolytic agents, including disulfide bond reducing agents, hydrogen bond breaking agents, and chaotropic ions, and their effect on rheological properties was assessed. Sodium thiocyanate led to 85-100% dissolution with the maximum retention of elasticity. Thiocyanate exposure did not result in demonstrable alterations in the size or shape of the mucus glycoproteins. Sodium thiocyanate is therefore recommended as a suitable dispersing agent for physiochemical studies of glycoprotein secretions.

General pharmacological properties of a new non-opiate antitussive: zipeprol (3024 CERM). I. Action on respiratory function and acute toxicity

1-(2-Methoxy-2-phenyl)-ethyl-4-(2-hydroxy-3-methoxy-3-phenyl)-propyl-iperazine-dihydrochloride (zipeprol, Respilene) is a substance of non-phenanthrenic chemical structure. In the cat, it antagonised cough induced by stimulation of the superior laryngeal nerve or by direct mechanical excitation of the sensitive tracheo-bronchial receptors. The efficacy of zipeprol after enteral administration made it possible both to establish good intestinal absorption and to rank it favourably in relation to several major antitussive reference products; codeine, codethyline, dextromethorphan, diphenhydramine and pentoxyverine. The activity of zipeprol was superior or equal to that of all these substances, excdept codeine. The antitussive properties appeared to be due to a central action. Other properties have been demonstrated which suggest at least a supplementary mechanism in the inhibition of cough, in addition to the central action. These consisted of slight antihistamine and anticholinergic properties, marked local-anesthetic potency and bronchospasmolytic activity. This latter property was demonstrated by the inhibition of histamine and serotonin induced bronchospasm in the guinea-pig. In vitro, using human sputum, zipeprol had a mucolytic action, shown by a decrease in sputum vis viscosity and lysis of DNA and AMPS fibrils. In the dog, at high doses, zipeprol unlike codeine, did not inhibit central stimulation of respiration by hypercapnia, in addition no modification of ventilatory dynamics or blood gases was seen. On the basis of these results, zipeprol can be considered as possessing no respiratory depressant effect even in the upper ranges of its antitussive doses.