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

Drug-Induced Kidney Stones and Crystalline Nephropathy: Pathophysiology, Prevention and Treatment

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favour crystallisation in the urine. Among them, drugs used for the treatment of patients with human immunodeficiency, namely atazanavir and other protease inhibitors, and sulphadiazine used for the treatment of cerebral toxoplasmosis, are the most frequent causes. Besides these drugs, about 20 other molecules may induce nephrolithiasis, such as ceftriaxone or ephedrine-containing preparations in subjects receiving high doses or long-term treatment. Calculi analysis by physical methods including infrared spectroscopy or X-ray diffraction is needed to demonstrate the presence of the drug or its metabolites within the calculi. Some drugs may also provoke heavy intra-tubular crystal precipitation causing acute renal failure. Here, the identification of crystalluria or crystals within the kidney tissue in the case of renal biopsy is of major diagnostic value. The second group includes drugs that provoke the formation of urinary calculi as a consequence of their metabolic effects on urinary pH and/or the excretion of calcium, phosphate, oxalate, citrate, uric acid or other purines. Among such metabolically induced calculi are those formed in patients taking uncontrolled calcium/vitamin D supplements, or being treated with carbonic anhydrase inhibitors such as acetazolamide or topiramate. Here, diagnosis relies on a careful clinical inquiry to differentiate between common calculi and metabolically induced calculi, of which the incidence is probably underestimated. Specific patient-dependent risk factors also exist in relation to urine pH, volume of diuresis and other factors, thus providing a basis for preventive or curative measures against stone formation.

Role of guaifenesin in the management of chronic bronchitis and upper respiratory tract infections

Guaifenesin, a mucoactive drug, acts by loosening mucus in the airways and making coughs more productive. It is used for relief of wet cough and chest congestion due to the common cold, and remains the only legally marketed expectorant in the US (per OTC Monograph). An ingredient in numerous over-the-counter (OTC) cough/cold medications, guaifenesin has a secondary indication for use in stable chronic bronchitis (professional indication). Clinical pharmacology and patient studies support the clinical utility of guaifenesin in respiratory conditions where mucus hypersecretion is prevalent: acute upper respiratory tract infections (URTIs), stable chronic bronchitis, and possibly rhinosinusitis. Guaifenesin has a well-established and favorable safety and tolerability profile in adult and pediatric populations. Its dosing range (200–400 mg 4-hourly, up to 6× daily) allows flexible dose titration to allow an increase of plasma concentrations. Multiple daily doses are needed to maintain 24-h therapeutic effect with immediate-release formulations. Extended-release guaifenesin tablet formulations are available, providing convenience with 12-hourly dosing and portability compared to liquids. Guaifenesin is considered as a safe and effective expectorant for the treatment of mucus-related symptoms in acute URTIs and stable chronic bronchitis. Its clinical efficacy has been demonstrated most widely in chronic respiratory conditions, where excess mucus production and cough are more stable symptoms. Progress is being made to establish clinical models and measures that are more appropriate for studying symptomatic relief with guaifenesin in acute respiratory infections. This will help generate the up-to-date and high-quality data needed to optimize guaifenesin’s effectiveness in established uses, and in new respiratory indications associated with mucus hypersecretion.

Guaifenesin stone matrix proteomics: a protocol for identifying proteins critical to stone formation

Drug-related kidney stones are a diagnostic problem, since they contain a large matrix (protein) fraction and are frequently incorrectly identified as matrix stones. A urine proteomics study patient produced a guaifenesin stone during her participation, allowing us to both correctly diagnose her disease and identify proteins critical to this drug stone-forming process. The patient provided three random midday urine samples for proteomics studies; one of which contained stone-like sediment with two distinct fractions. These solids were characterized with optical microscopy and Fourier transform infrared spectroscopy. Immunoblotting and quantitative mass spectrometry were used to quantitatively identify the proteins in urine and stone matrix. Infrared spectroscopy showed that the sediment was 60 % protein and 40 % guaifenesin and its metabolite guaiacol. Of the 156 distinct proteins identified in the proteomic studies, 49 were identified in the two stone-components with approximately 50 % of those proteins also found in this patient's urine. Many proteins observed in this drug-related stone have also been reported in proteomic matrix studies of uric acid and calcium containing stones. More importantly, nine proteins were highly enriched and highly abundant in the stone matrix and 8 were reciprocally depleted in urine, suggesting a critical role for these proteins in guaifenesin stone formation. Accurate stone analysis is critical to proper diagnosis and treatment of kidney stones. Many matrix proteins were common to all stone types, but likely not related to disease mechanism. This protocol defined a small set of proteins that were likely critical to guaifenesin stone formation based on their high enrichment and high abundance in stone matrix, and it should be applied to all stone types.

Acute renal failure after ingestion of guaifenesin and dextromethorphan

BACKGROUND

Guaifenesin is a common nonprescription medication that has been implicated in drug-induced nephrolithiasis. Dextromethorphan, a nonprescription antitussive found in some guaifenesin-containing preparations, is increasingly recognized as a substance of abuse by many youth and young adults. Renally excreted medications known to have poor solubility in urine have the potential to precipitate when ingested in large quantity, leading to acute obstruction of the ureters and renal failure.

OBJECTIVE

We describe the case of a 22-year-old male who developed severe bilateral flank pain, hematuria, and oliguria after an isolated recreational ingestion of guaifenesin and dextromethorphan.

CASE REPORT

The patient was found to have bilateral ureteral obstruction and acute renal failure, suspected to be secondary to precipitation of medication metabolites in the urine.

CONCLUSIONS

This case highlights the potential for acute renal failure secondary to guaifenesin and dextromethorphan abuse.

Urological complications of illicit drug use

Illicit drug use is prevalent worldwide; over 24 million people are estimated to have used recreational drugs during the past month in the UK and USA alone. Illicit drug use can result in a wide spectrum of potential medical complications that include many urological manifestations. To ensure optimal care and treatment, urologists need to be cognizant of these complications in their patients, particularly among youths. Ketamine uropathy is thought to affect over one-quarter of ketamine users and can lead to severe lower urinary tract symptoms, as well as upper tract obstruction. Cannabis use has been associated with an increased risk of bladder cancer, prostate cancer and nonseminomatous germ cell tumours in case-control studies. Fournier's gangrene has been reported following injection of heroin and cocaine into the penis. Excessive use of cough medicines can lead to the development of radiolucent stones composed of ephedrine, pseudoephedrine and guaifenesin. As the current evidence is mostly limited to case reports and case series, future epidemiological studies are needed to fully address this issue.

Recommendations for the proper use of nonprescription cough suppressants and expectorants in solid-organ transplant recipients

OBJECTIVE

To describe the pharmacology and safety of oral over-the-counter cough suppressants and expectorants and to present recommendations for the use of these agents in solid-organ transplant recipients based on the potential for adverse drug reactions or drug-disease interactions.

DATA SOURCES AND EXTRACTION

Data from journal articles and other sources describing the pharmacology and safety of over-the-counter cough suppressants and expectorants, drug-drug interactions with immunosuppressive agents, and drug-disease state interactions are reviewed.

DATA SYNTHESIS

Potential and documented drug-drug interactions between immunosuppressive agents and over-the-counter cough medications guaifenesin, dextromethorphan, diphenhydramine, and codeine were evaluated on the basis of pharmacokinetic and pharmacodynamic principles. Interactions between these cough medications and the physiological changes in the body following transplantation also were examined.

CONCLUSION

Diphenhydramine requires additional monitoring when used to treat cough in transplant recipients owing to its anticholinergic properties and the potential for interactions with cyclosporine. Dextromethorphan can be used in most transplant recipients, although greater caution should be exercised if the patient has undergone liver transplant or has liver impairment. Guaifenesin can be used in transplant recipients but should be used with caution in patients receiving kidney or lung transplants and in patients with renal impairment. Codeine combined with guaifenesin is another option for cough and can be used in most transplant patients although those with reduced renal function should be monitored carefully for adverse events.

Recommendations for the Proper Use of Nonprescription Cough Suppressants and Expectorants in Solid-Organ Transplant Recipients

Objective

To describe the pharmacology and safety of oral over-the-counter cough suppressants and expectorants and to present recommendations for the use of these agents in solid-organ transplant recipients based on the potential for adverse drug reactions or drug-disease interactions.

Data Sources and Extraction

Data from journal articles and other sources describing the pharmacology and safety of over-the-counter cough suppressants and expectorants, drug-drug interactions with immunosuppressive agents, and drug-disease state interactions are reviewed.

Data Synthesis

Potential and documented drug-drug interactions between immunosuppressive agents and over-the-counter cough medications guaifenesin, dextromethorphan, diphenhydramine, and codeine were evaluated on the basis of pharmacokinetic and pharmacodynamic principles. Interactions between these cough medications and the physiological changes in the body following transplantation also were examined.

Conclusion

Diphenhydramine requires additional monitoring when used to treat cough in transplant recipients owing to its anticholinergic properties and the potential for interactions with cyclosporine. Dextromethorphan can be used in most transplant recipients, although greater caution should be exercised if the patient has undergone liver transplant or has liver impairment. Guaifenesin can be used in transplant recipients but should be used with caution in patients receiving kidney or lung transplants and in patients with renal impairment. Codeine combined with guaifenesin is another option for cough and can be used in most transplant patients although those with reduced renal function should be monitored carefully for adverse events.

Safety assessment of drug metabolites: Characterization of chemically stable metabolites

Drug molecules are typically subjected to a variety of biotransformation reactions, and the metabolites formed through these reactions must be considered when conducting safety testing programs for new chemical entities. Metabolites that are chemically stable sometimes have pharmacological activity profiles similar to those of the parent compound but rarely have potent activity against off-target receptors that is unique relative to the parent profile. This fact argues for the thorough testing of drug metabolites for their pharmacological activity. It also argues for a significantly lower need for the thorough characterization and quantitation of stable metabolites not thought to substantially contribute to the pharmacodynamic effect. Given the tremendous resource requirements involved in the thorough characterization of drug metabolites, a more flexible, tiered approach to stable metabolite characterization would seem to provide the best utilization of resources while still allowing a complete evaluation of the toxicological profile of a new drug.

Involvement of enzymes other than CYPs in the oxidative metabolism of xenobiotics

Although the majority of oxidative metabolic reactions are mediated by the CYP superfamily of enzymes, non-CYP-mediated oxidative reactions can play an important role in the metabolism of xenobiotics. The (major) oxidative enzymes, other than CYPs, involved in the metabolism of drugs and other xenobiotics are: the flavin-containing monooxygenases, the molybdenum hydroxylases (aldehyde oxidase and xanthine oxidase), the prostaglandin H synthase, the lipoxygenases, the amine oxidases (monoamine, polyamine, diamine and semicarbazide-sensitive amine oxidases) and the alcohol and aldehyde dehydrogenases. In a similar manner to CYPs, these oxidative enzymes can also produce therapeutically active metabolites and reactive/toxic metabolites, modulate the efficacy of therapeutically active drugs or contribute to detoxification. Many of them have been shown to be important in endobiotic metabolism, and, consequently, interactions between drugs and endogenous compounds might occur when they are involved in drug metabolism. In general, most non-CYP oxidative enzymes appear to be noninducible or much less inducible than the CYP system, although some of them may be as inducible as some CYPs. Some of these oxidative enzymes exhibit polymorphic expression, as do some CYPs. It is possible that the contribution of non-CYP oxidative enzymes to the overall metabolism of xenobiotics is underestimated, as most investigations of drug metabolism in discovery and lead optimisation are performed using in vitro test systems optimised for CYP activity.

Lithiases médicamenteuses

Drug-induced renal calculi represent 1-2% of all renal calculi. They include two categories: those resulting from the urinary crystallisation of a highly excreted, poorly soluble drug or metabolite, and those due to the metabolic effects of a drug. Indinavir, used in HIV-infected patients, sulfonamides, especially sulfadiazine, and triamterene, which is less prescribed today, are the most frequent. Besides these drugs, about twenty other molecules, among them silicate-containing drugs and some antibiotics have been reported in patients receiving high doses or long-term treatments. Calculi analysis by physical methods such as infrared spectroscopy or x-ray diffraction can demonstrate the presence of the drug or its metabolites inside the calculi. In those calculi due to the metabolic effects of a drug, diagnosis relies on both stone analysis and clinical inquiry. Incidence of such calculi is probably underestimated, especially those due to calcium/vitamin D supplements or carbonic anhydrase inhibitors. Drug-induced calculi occur more often during high-dose or long term treatments, but there are also patient-related risk factors in relation to urine pH, urine output and other parameters, which can provide a basis for preventive treatment of such calculi. A better knowledge of these lithogenic complications of treatments and of solubility characteristics of drugs should reduce the incidence of drug-induced nephrolithiasis, especially in patients with identified risk factors.

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.

Bilateral guaifenesin ureteral calculi

We report on a patient with bilateral ureteral calculi composed of guaifenesin metabolite as determined by infrared spectroscopy. These stones may be associated with excessive guaifenesin intake related to the current popularity of ephedrine preparations.

Resolution of ephedrine stones with dissolution therapy

A patient with a history of ingesting large quantities of an over-the-counter stimulant developed renal calculi that on further analysis, after stone passage, revealed increased amounts of ephedrine. Over the course of 7 months, all of the patient's ephedrine stones were managed successfully by alkalinization. Similar to previously reported ephedrine calculi, these stones were radiolucent on x-ray imaging, but their course was monitored on serial nonenhanced computed tomography scans. We believe this to be the first reported use of alkaline therapy for the dissolution of renal stones containing ephedrine.