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Abuse of guaifenesin-containing medications generates an excess of a carboxylate salt of beta-(2-methoxyphenoxy)-lactic acid, a guaifenesin metabolite, and results in urolithiasis.

OBJECTIVES: Several urinary calculi were submitted to our institution for compositional analysis. The typical techniques of analysis, polarized light microscopy, electron microprobe analysis, and infrared spectroscopy proved inadequate for a definitive identification. As a result, a more detailed organic analysis was conducted to determine the exact chemical structure of the material. METHODS: Infrared spectroscopy and mass spectrometric analysis were carried out on the solid material, providing information concerning the functional groups and the molecular mass of the organic constituent and its components. The stone was solubilized in deuterated solvents and analyzed by nuclear magnetic resonance spectroscopy, which resulted in a definitive chemical structure. RESULTS: The spectroscopic analysis indicated that the stones were composed of a calcium salt of beta-(2-methoxyphenoxy)-lactic acid, a metabolite of the pharmaceutical guaifenesin, which is used as an expectorant. CONCLUSIONS: Guaifenesin, an expectorant common in over-the-counter cold and allergy remedies, can cause urolithiasis if taken in excess. Discussions with physicians and their patients confirmed that most patients admitted to taking large doses of guaifenesin-containing medications.

Adolescent↗

Determination of the structure of a synthetic impurity in guaifenesin: modification of a high-performance liquid chromatographic method for phenylephrine hydrochloride, phenylpropanolamine hydrochloride, guaifenesin, and sodium benzoate in dosage forms.

An impurity present in all commercial guaifenesin-containing dosage forms examined was isolated and identified as 2-(2-methoxyphenoxy) 1,3-propanediol (VI). The eluant of a previously developed stability-indicating liquid chromatographic method for phenylephrine hydrochloride (I), phenylpropanolamine hydrochloride (II), and guaifenesin (III) was modified to yield a better separation between phenylpropanolamine and the impurity. The method was expanded to include sodium benzoate (IV), a preservative found in some liquid formulations.

Benzoates↗

Guaifenesin: cardiopulmonary effects and plasma concentrations in horses.

We determined the cardiopulmonary changes in horses given guaifenesin alone and in the same horses given xylazine (IV) immediately before administration of guaifenesin. In addition, plasma guaifenesin concentrations were determined in horses and 2 pregnant mares and compared with previously published values in ponies. The dose of guaifenesin necessary to produce lateral recumbency in adult horses was 134 +/- 34 mg/kg (mean +/- SD). The administration of guaifenesin caused insignificant (P less than 0.05) changes in heart rate, respiratory rate, right atrial pressure, pulmonary arterial pressure, and cardiac output. Systolic, diastolic, and mean arterial blood pressures were significantly (P less than 0.05) decreased. Arterial partial pressure of oxygen (PaO2) was transiently, but significantly (P less than 0.05), reduced. The administration of xylazine (IV) to the horses before they were given guaifenesin reduced the dose of guaifenesin necessary to produce lateral recumbency to 88 +/- 10 mg/kg. In these horses, there were significant transient decreases in heart rate, respiratory rate, cardiac output, and PaO2. Central venous pressure remained significantly (P less than 0.05) increased, whereas systolic, diastolic, and mean arterial blood pressures were significantly (P less than 0.05) decreased at all times. In horses given guaifenesin alone, plasma concentrations at the time of lateral recumbency were 313 +/- 108 microgram/ml, and in those given xylazine-guaifenesin, the concentrations of the drug were 277 +/- 83 microgram/ml. Neonatal concentrations of guaifenesin were approximately 30% of that of the mare immediately after delivery, indicating that significant amounts of guaifenesin cross the placental barrier in the mare.

Animals↗

HPLC determination of guaifenesin with selected medications on underivatized silica with an aqueous-organic mobile phase.

A high performance liquid chromatography procedure has been developed for the simultaneous determination of guaifenesin pseudoephedrine-dextromethorphan and guaifenesin-pseudoephedrine in commercially available capsule dosage forms and guaifenesin-codeine in a commercial cough syrup dosage form. The separation and quantitation are achieved on a 25-cm underivatized silica column using a mobile phase of 60:40%) v/v 6.25 mM phosphate buffer, pH 3.0 - acetonitrile at a flow rate of 1 ml min(-1) with detection of all analytes at 216 nm. The separation is achieved within 10 min for each drug mixture. The method showed linearity for the guaifenesin-pseudoephedrine-dextromethorphan mixture in the 50-200, 7.5-30 and 2.5-10, microg ml(-1) ranges, respectively. The intra- and inter-day RSDs ranged from 0.23 to 4.20%, 0.18 to 2.85%, and 0.13 to 5.04% for guaifenesin, pseudoephedrine, and dextromethorphan, respectively. The guaifenesin pseudoephedrine mixture yielded linear ranges of 25-100 and 3.75-15 microg ml(-1) and intra- and inter-day RSDs ranged from 0.65 to 4.18% and 0.23 to 3.00% for guaifenesin and pseudoephedrine, respectively. The method showed linearity for the guaifenesin-codeine mixture in the 25-100 and 2.5-10 microg ml(-1) ranges and RSDs ranged from 0.37 to 4.25% and 0.14 to 2.08% for guaifenesin and codeine, respectively.

Antitussive Agents↗

Guaifenesin enhances the analgesic potency of paracetamol in mice.

AIM OF INVESTIGATION: Guaifenesin is used as an expectorant and it has been reported to possess muscle relaxant and sedative activity. Guaifenesin has been used as a component of composite OTC analgesics containing paracetamol for many years. The aim of our study was to ascertain effects of guaifenesin on paracetamol analgesic activity and locomotor performance. METHODS: Antinociceptive efficacy was tested in mice using an acetic acid (0.7%) writhing test. Locomotor performance was tested in rota-rod test and activity cage. All drugs were given orally and tested in mice. RESULTS: In combination with a subeffective dose of guaifenesin (200 mg/kg), the ED(50) for paracetamol in the writhing test was significantly lower (82.2 mg/kg) than that of paracetamol administered alone (233.7 mg/kg). Guaifenesin alone did not show an analgesic effect. Guaifenesin did not produce statistically significant locomotor impairment in the rota-rod test at doses enhancing analgesic activity of paracetamol, although there was a trend for decreased locomotor activity in activity cage. CONCLUSION: The present results indicate that guaifenesin may enhance analgesic activity of paracetamol.

Acetaminophen↗

Alterations of nasal mucociliary clearance in association with HIV infection and the effect of guaifenesin therapy.

OBJECTIVES: To determine if human immunodeficiency virus (HIV) infection is associated with a prolonged mucociliary clearance time (MCT) and to evaluate the effect of guaifenesin on MCT in HIV+ patients. STUDY DESIGN: A cross-sectional study comparing HIV+ and HIV- volunteers followed by a prospective, randomized, double-blind, placebo-controlled study of HIV+ patients before and after guaifenesin treatment. METHODS: Twenty-five HIV+ patients and 29 HIV- controls were enrolled and MCT was measured using the saccharin method. A separate group of 20 HIV+ patients participated in the second arm of the study and underwent saccharin testing before and after a 3-week course of guaifenesin or placebo. All study participants completed a medical history questionnaire, a sinonasal symptom (SNOT-16) survey, and were examined with both anterior rhinoscopy and rigid nasal endoscopy. RESULTS: There was a significant difference (P < .002) in the MCT between the HIV+ group (13.3 +/- SD 7.5 minutes) and the HIV- controls (9.2 +/- SD 3.9 minutes). The difference in MCT between the guaifenesin and placebo groups did not reach statistical significance (P >.05). The HIV+ group had a higher SNOT-16 score compared to HIV- controls (21.1 vs. 7.4, P < .001). Guaifenesin therapy in HIV+ patients led to a significant improvement in the SNOT-16 score (P < .05). CONCLUSIONS: Compared to HIV- controls, HIV+ patients have a prolonged MCT and more sinonasal symptoms as indicated by a higher SNOT-16 score. Guaifenesin therapy was associated with improved SNOT-16 scores, although there was not a detectable improvement in MCT. Use of guaifenesin in HIV+ patients with sinonasal disease may lead to improved patient perception of quality of life.

Adult↗

Hemolytic potential of guaifenesin in cattle.

The hemolytic effect on bovine red blood cells of 5%, 10%, and 15% guaifenesin solutions in 5% dextrose, 0.9% saline (NaCl), or distilled water was determined in vitro at 2 plasma concentrations (250 micrograms/ml, 500 micrograms/ml). A solution of 5% guaifenesin in a 5% dextrose solution or 5% guaifenesin in 0.9% saline produced minimal hemolysis in vitro. The amount of hemolysis of bovine red blood cells in vitro was related to the concentration of guaifenesin, diluent (5% dextrose, 0.9% NaCl, distilled water) and the plasma concentration of guaifenesin. In addition, plasma hemoglobin was determined in 4 adult dairy cows following the IV administration of 5% and 10% guaifenesin. These studies suggest that a solution of 5% guaifenesin in 5% dextrose is the most suitable solution for clinical use in cattle.

Animals↗

Determination of guaifenesin in human plasma by liquid chromatography in the presence of pseudoephedrine.

A sensitive and specific liquid chromatography (LC) procedure was developed and validated for the determination of guaifenesin in human plasma in the presence of pseudoephedrine. Guaifenesin was extracted from plasma at pH 6.9-7.1 using methanol-methylene chloride (5:95, v/v) containing the internal standard mephenesin and pseudoephedrine. The organic layer was separated and evaporated to dryness and the residue reconstituted with the mobile phase containing methanol-acetonitrile-phosphate buffer (0.05 M) (11:11:78, v/v/v) containing 4 mM heptane sulphonic acid and 1% glacial acetic acid. The separation was performed on a mu Bondapak C18 column. The flow rate was 1.0 ml min-1. The retention times for guaifenesin and mephenesin were 7.9 and 15.7 min, respectively. Linearity of response was observed in the concentration ranges of 50-1000 ng ml-1 and 1-4 micrograms ml-1. Accuracy was within 15.4% of the true value for the inter-day and intra-day analysis. The precision, as measured by the RSD, ranged from 4.8 to 8.7% for intra-day. The reproducibility of inter-day ranged from 5.0 to 8.4%. The per cent recovery from plasma ranged from 88.6 to 97.6. Data are presented to illustrate the practicality of the method for the evaluation of guaifenesin plasma levels in the presence of pseudoephedrine after multiple oral administration of two sustained release tablets containing 600 mg of guaifenesin per tablet to six male healthy volunteers. The mean half-life of guaifenesin in human subjects was found to be 2.88 h and ranged from 1.36 to 5.25 h.

Chromatography, Liquid↗

Voltammetric assay of Guaifenesin in pharmaceutical formulation.

The electrochemical oxidation of Guaifenesin in a pharmaceutical formulation containing Guaifenesin has been carried out in Britton-Robinson buffer (BRB) (0.04 mol L-1) on platinum electrode. Guaifenesin exhibits a well-defined irreversible oxidation peak at 0.924 V/ref. The influence of pH on the oxidation of Guaifenesin was studied in BRB (pH range 2-5). A method for the analysis of Guaifenesin in BRB (0.04 mol L-1, pH 2), which allows quantification over the range 20-60 microg mL-1, was proposed and successfully applied to the determination of Guaifenesin in syrup with mean recovery and relative standard deviation of 103.3% and 1.32%, respectively.

Calibration↗

Pharmacokinetics and cardiopulmonary effects of guaifenesin in donkeys.

Five donkeys and three horses were given guaifenesin, intravenously, by gravity administration, until recumbency was produced. The time and dose required to produce recumbency, recovery time to sternal and standing were recorded. Blood samples were collected for guaifenesin assay at 10, 20, 30, 40, 50, 60 min, and 2, 3, 4 and 6 h after guaifenesin administration. Serum was analysed for guaifenesin using HPLC and pharmacokinetic values were calculated using a computer software package (RSTRIP). In donkeys, heart and respiratory rates and blood pressures were recorded before and at 5-min intervals during recumbency. Arterial blood samples were collected before and at 5 and 15 min intervals during recumbency for analysis of pH, CO2, and O2. ANOVA was used to evaluate dynamic data, while t-tests were used for kinetic values. Respiratory rate was decreased significantly during recumbency, but no other significant changes from baseline occurred. The mean (+/- SD) recumbency dose of guaifenesin was 131 mg/kg (27) for donkeys and 211 mg/kg (8) for horses. Recovery time to sternal (min) was 15 (SD, 11) for donkeys and 34 (SD, 1.4) for horses. Time to standing was 32 min for donkeys and 36 min for horses. Calculation of AUC (area under the concentration-time curve) microgram/mL) (dose-dependent variable) was 231 (SD, 33) for donkeys and 688 (SD, 110) for horses. The clearance (CL) (mL/h.kg) was 546 (SD, 73) for donkeys, which was significantly different from 313 (SD, 62) for horses. Mean residence time (MRT) (h) was 1.2 (SD, 0.1) for donkeys and 2.6 (SD, 0.5) for horses. Volume of distribution Vd(area) (mL/kg) was 678 (SD, 92) for donkeys and 794 (SD, 25) for horses. At the rate of administration used in this study, donkeys required less guaifenesin than horses to produce recumbency, but cleared it more rapidly.

Animals↗

Ephedrine- and guaifenesin-induced nephrolithiasis.

OBJECTIVES: Ephedrine and guaifenesin are herbal supplements that have experienced increased use over the past decade. Ephedrine has been used as a stimulant and weight-loss product, guaifenesin as an expectorant and cough suppressant; both are found in combination in many antitussives and expectorants. This paper reviews the reported cases of ephedrine- and guaifenesin-induced nephrolithiasis, as well as the diagnostic techniques and treatments that have been successfully used for these stones. DESIGN: A systematic review of the literature pertaining to nephrolithiasis and the compounds ephedrine and guaifenesin was conducted. RESULTS: Ephedrine and guaifenesin use results in over 35% of urinary stones that are related to pharmaceutical metabolites, and collectively are present in 0.1% of all urinary stones. These calculi are radiolucent, requiring the use of computerized tomography (CT scan) for diagnosis. Alkalinization therapy offers an alternative to surgical intervention and may have a role in prevention of recurrence. CONCLUSIONS: Ephedrine and guaifenesin have been shown to cause nephrolithiasis in cases of abuse when taken individually or in combination. It is important for the clinician to be aware of the potential for these compounds to cause nephrolithiasis.

Antitussive Agents↗

Guaifenesin- and ephedrine-induced stones.

PURPOSE: We report a new type of drug-induced stone that is caused by overconsumption of preparations containing guaifenesin and ephedrine. MATERIALS AND METHODS: Clinical and stone analysis data from the Molecular Structure Laboratory at the Veterans Affairs Medical Center in Milwaukee, Wisconsin, were reviewed. Stone analysis was performed by Fourier transform infrared spectroscopy, high-resolution X-ray crystallographic powder diffraction, or both. The urine and stone material from one of the subjects were analyzed with high-performance liquid chromatography. RESULTS: Stone analysis from seven patients demonstrated metabolites of guaifenesin. High-performance liquid chromatography revealed that the stone and urine from one subject had a high content of guaifenesin metabolites and a small amount of ephedrine. Demographic data were available on five patients. Three had a history of alcohol or drug dependency. All were consuming over-the-counter preparations containing ephedrine and guaifenesin. Four admitted to taking excessive quantities of these agents, mainly as a stimulant. Hypocitraturia was identified in two individuals subjected to urinary metabolic testing. These stones are radiolucent on standard X-ray imaging but can be demonstrated on unenhanced CT. Shockwave lithotripsy was performed in two patients, and the calculi fragmented easily. CONCLUSIONS: Individuals consuming large quantities of preparations containing ephedrine and guaifenesin may be at risk to develop stones derived mainly from metabolites of guaifenesin and small quantities of ephedrine. These patients may be prone to drug or alcohol dependency.

Adult↗

Effects of 5% and 10% guaifenesin infusion on equine vascular endothelium.

Twelve horses of various breeds and either sex were anesthetized with xylazine and ketamine injected into a median or lateral thoracic vein. During anesthesia, with the horse in sternal recumbency, a 14-gauge, 8.9 cm catheter was inserted into each jugular vein by using aseptic technique. Guaifenesin in water (100 mg/kg or a maximum dose of 50 grams) was infused into one jugular vein and an equal volume of 0.9% saline solution was infused into the other jugular vein. Seven horses received 10% guaifenesin, and five horses received 5% guaifenesin. The catheters were removed before the horses recovered from anesthesia. The horses were euthanatized approximately 48 hours later, and the jugular veins were removed for histologic examination. Adherent thrombus material was observed in all veins exposed to 10% guaifenesin and in one vein exposed to 5% guaifenesin. No evidence of thrombus was observed in four veins infused with 5% guaifenesin or in those infused with saline solution. These findings are of particular significance with horses at increased risk for thrombosis or thrombophlebitis.

Animals↗

Effect of guaifenesin on cough reflex sensitivity.

BACKGROUND: Guaifenesin, a commonly used agent for the treatment of cough, is termed an expectorant since it is believed to alleviate cough discomfort by increasing sputum volume and decreasing its viscosity, thereby promoting effective cough. Despite its common usage, relatively few studies, yielding contrasting results, have been performed to investigate the action and efficacy of guaifenesin. STUDY OBJECTIVES: To evaluate the effect of guaifenesin on cough reflex sensitivity. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Academic medical center. PARTICIPANTS: Fourteen subjects with acute viral upper respiratory tract infection (URI) and 14 healthy volunteers. INTERVENTIONS: On 2 separate days, subjects underwent capsaicin cough challenge 1 to 2 h after receiving a single, 400-mg dose (capsules) of guaifenesin or matched placebo. MEASUREMENTS AND RESULTS: The concentration of capsaicin inducing five or more coughs (C(5)) was determined. Among subjects with URI, mean (+/- SEM) log C(5) after guaifenesin and placebo were 0.92 +/- 0.17 and 0.66 +/- 0.14, respectively (p = 0.028). No effect on cough sensitivity was observed in healthy volunteers. CONCLUSIONS: Our results demonstrate that guaifenesin inhibits cough reflex sensitivity in subjects with URI, whose cough receptors are transiently hypersensitive, but not in healthy volunteers. Possible mechanisms include a central antitussive effect, or a peripheral effect by increased sputum volume serving as a barrier shielding cough receptors within the respiratory epithelium from the tussive stimulus.

Adult↗

Sensitive liquid chromatography-tandem mass spectrometry method for the simultaneous determination of paracetamol and guaifenesin in human plasma.

A rapid and sensitive method for the simultaneous determination of paracetamol and guaifenesin in human plasma was developed and validated, using high-performance liquid chromatographic separation with tandem mass spectrometric detection. After extracted from plasma samples by diethyl ether-dichloromethane (3:2, v/v), the analytes and internal standard osalmide were chromatographed on a C18 column. Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via atmospheric pressure chemical ionization (APCI). The method was linear in the concentration range of 0.05-20.0 microg/ml for paracetamol and 5.0-2000.0 ng/ml for guaifenesin. The intra- and inter-day precision was within 14% for both paracetamol and guaifenesin. The assay accuracy was within +/-2.4% for the analytes. This is the first assay method described for the simultaneous determination of paracetamol and guaifenesin in plasma using one chromatographic run. The method was successfully employed in a pharmacokinetic study after an oral administration of a multicomponent formulation, containing 650 mg paracetamol, 200 mg guaifenesin, 60 mg pseudoephedrine and 20 mg dextrorphan.

Acetaminophen↗

High-pressure liquid chromatographic assay of dextromethorphan hydrobromide, guaifenesin, and sodium benzoate in an expectorant syrup.

An ion-pair reversed-phase high-pressure liquid chromatographic assay is developed that allows simultaneous quantitation of guaifenesin, dextromethorphan hydrobromide, and sodium benzoate in an expectorant syrup. The method is rapid and accurate. Average recoveries of 99.6, 99.8, and 99.7% with relative standard deviations of 0.5, 0.9, and 0.2% are obtained for guaifenesin, dextromethorphan hydrobromide, and sodium benzoate, respectively, from laboratory prepared samples. Chromatographic conditions are selected to afford a pH that provides adequate separation of guaifenesin, dextromethorphan hydrobromide, sodium benzoate, and sodium saccharin and a detection wavelength that effectively compensates for the great disparity in quantity between guaifenesin and dextromethorphan hydrobromide present in syrups. The relationships between the retention volume of dextromethorphan hydrobromide and the alkyl chain length as well as the concentration of the counterion are studied. The retention profiles for sodium saccharin, guaifenesin, sodium benzoate, and dextromethorphan hydrobromide in the apparent pH range of 2.5 to 6.6 are established.

Benzoates↗

Effects of guaifenesin on nasal mucociliary clearance and ciliary beat frequency in healthy volunteers.

STUDY OBJECTIVE: Mucociliary clearance is an important host defense function of the upper respiratory tract that requires the coordinated beating of cilia and results in the transport of mucus to the oropharynx. Guaifenesin is a commonly prescribed drug that is reported to improve the clearance of respiratory secretions. We hypothesized that guaifenesin increases nasal mucociliary clearance related to increases in ciliary beat frequency (CBF) and that a direct relationship exists between nasal CBF and nasal mucociliary clearance. DESIGN: Double-blind placebo-controlled crossover study. PARTICIPANTS: Ten healthy volunteers with a previous history of sinus disease. INTERVENTIONS: Subjects received guaifenesin or placebo on days 1 to 7 or days 14 to 21. MEASUREMENTS AND RESULTS: In vivo saccharine transit time (STT) was measured by noting the time in minutes required for the subject to taste a saccharin particle placed on the inferior turbinate of the naris. The CBF was determined by video microscopy on ten separate groups of beating ciliated nasal mucosal cells obtained by brushing immediately after each STT determination. We found that there was no significant change between the guaifenesin-or placebo-treated groups from baseline values of STT (p = 0.94) or CBF (p = 0.46). Regression analysis demonstrated no relationship between STT and CBF for repeated measures within subjects (mean r2 = 0.18; mean p = 0.66) and between STT and CBF when all paired measurements were combined across subjects (r2 = 0.47; p = 0.46). CONCLUSION: We conclude that guaifenesin exerts no measurable effect on in vivo nasal mucociliary clearance or ex vivo nasal ciliary motility in healthy volunteers with previous sinus disease. In addition, there appears to be no relationship between nasal STT measured in vivo and CBF measured ex vivo. The lack of correlation is most likely due to variations in CBF related to sampling artifacts introduced by the nasal brushing process.

Cilia↗

Antitussive effect of guaifenesin in young adults with natural colds. Objective and subjective assessment.

The efficacy of guaifenesin in reducing cough frequency in young adults with acute respiratory disease was evaluated by both an objective cough counting system and a questionnaire. A guaifenesin cough preparation and the syrup vehicle were administered in a double-blind manner. Coughs were recorded on tape over a 24-hour baseline evaluation period and a 36-hour treatment period for 42 patients. A pronounced diurnal variation in cough frequency was observed. The evaluation of efficacy was based upon comparisons between equivalent six-hour time periods of successive days. No antitussive effect of guaifenesin was demonstrated. The questionnaire was administered to 65 patients, including the 42 whose coughs were recorded. Of 26 patients with productive cough receiving guaifenesin, 25 (96 percent) reported a decrease in sputum thickness compared to 13 (54 percent) of 24 patients receiving the vehicle (p = 0.01, Fisher exact test). Twenty-three of 26 (88 percent) patients receiving guaifenesin also reported reduction in sputum quantity compared to 15 of 24 (62.5 percent) receiving the vehicle (p = 0.07, Fisher exact test). The diurnal variation in cough frequency measured by the tape recording was not apparent from the subjective cough frequency estimates obtained by the questionnaire.

Adolescent↗