What can clinicians learn from therapeutic studies about the treatment of acute oral methotrexate poisoning?

Navigating methotrexate toxicity: Examining the therapeutic roles of folinic acid and glucarpidase

Methotrexate (MTX) toxicity varies depending on factors such as dosing frequency (acute or repeated), dosage (low or high) and the administration route (oral, parenteral or intrathecal). Renal impairment can trigger or exacerbate MTX toxicity. Acute oral low-dose MTX (LDMTX) overdoses seldom lead to toxicity due to the saturable maximal bioavailable dose, but toxicity risks increase with repeated low doses (>3 days), high-dose MTX (HDMTX) or intrathecal poisoning. Folinic acid shares MTX transporters in the gut and cells and bypasses the MTX-induced dihydrofolate reductase inhibition. The required folinic acid dosage differs for low-dose and high-dose MTX toxicities. Acute LDMTX poisoning rarely requires folinic acid, while chronic LDMTX poisoning needs low-dose folinic acid until cellular function is restored. In HDMTX toxicities, early intravenous folinic acid administration is recommended, with dose and duration being guided by MTX concentrations and clinical improvement. In intrathecal MTX poisoning, folinic acid should be administered intravenously. Glucarpidase, a recombinant bacterial enzyme, has a high affinity for MTX and folate analogues in the intravascular or intrathecal systems. It decreases serum MTX concentrations by 90%-95% within 15 min. Its primary indication is for intrathecal MTX poisoning. It is rarely indicated in HDMTX toxicity unless patients have renal injury. However, there is no literature evidence supporting its use in HDMTX poisoning. Its use is limited by its significant cost and lack of availability. Haemodialysis can be potentially useful for MTX removal in cases where glucarpidase is not available. Additionally, fluid hydration, renal support and urine alkalinization are important adjunctive therapies for managing MTX toxicities.

Advances of autoimmune rheumatic diseases related to malignant tumors

BACKGROUND

Malignant neoplasms are a well-recognized global public health concern, with significant impacts on human health and quality of life. The interplay between tumors and autoimmune rheumatic diseases is complex, and the resulting tumor-associated rheumatic diseases represent a rare and intricate group of conditions that occur in the context of malignant tumors. In addition, various rheumatic diseases can arise as a consequence of oncology treatment. These diseases present with intricate clinical manifestations and pathological features, often rendering them challenging to diagnose and impacting patients' quality of life. Despite this, they have yet to be fully recognized.

METHODS

This article presents a literature review of published original articles and review articles concerning paraneoplastic rheumatic syndromes and rheumatic diseases associated with cancer treatment. We conducted a comprehensive literature search in PubMed, Web of Science and Google Scholar databases, excluding duplicated and irrelevant studies. In cases of duplicated research, we selected articles with higher impact factors for the review.

RESULTS

This review focuses on the clinical features, diagnosis, and treatment of paraneoplastic rheumatic diseases, as well as the pathogenesis of these diseases. Additionally, we summarize the autoimmune rheumatic diseases associated with cancer treatment. Ultimately, the goal of this review is to enhance recognition and improve the management of autoimmune rheumatic diseases related to tumors.

A pooled subgroup analysis of glucarpidase treatment in 86 pediatric, adolescent, and young adult patients receiving high-dose methotrexate therapy in open-label trials

BACKGROUND

Delayed methotrexate elimination can occur in patients undergoing high-dose methotrexate cancer treatment. Effectiveness of glucarpidase for rapidly reducing methotrexate concentrations was shown in compassionate-use trials in patients aged 0-84 years.

METHODS

We performed post hoc analyses of infants (≥28 days to <2 years), children (≥2 to <12 years), adolescents (≥12 to <15 years), and young adults (≥15 to <25 years) from four multicenter, open-label, single-arm, glucarpidase compassionate-use trials. Patients had toxic methotrexate levels due to delayed methotrexate elimination and/or renal dysfunction, and received glucarpidase (50 U/kg). The primary endpoint was clinically important reduction (CIR) in plasma methotrexate (methotrexate ≤1 μmol/L at all post-glucarpidase measurements) based on high-performance liquid chromatography.

RESULTS

Among 86 patients included in efficacy analyses, CIR was achieved by zero of one infant (0.0%), five of 16 children (31.3%), seven of 24 adolescents (29.2%), and 26/45 young adults (57.8%). Median methotrexate reduction was 98.7% or higher in each group 15 minutes post-glucarpidase. Patients with pre-glucarpidase methotrexate less than 50 μmol/L (35/42, 83.3%) were more likely to achieve CIR than those with methotrexate 50 μmol/L or higher (1/37, 2.7%). The most common treatment-related adverse event was paresthesia, occurring in three adolescents (4.5%) and six young adults (5.2%). No other treatment-related adverse event occurred in 5% or higher of any age group.

CONCLUSION

After accounting for pre-glucarpidase methotrexate levels, glucarpidase efficacy at inducing CIR in pediatric/young adult patients was consistent, with efficacy observed in the overall study population (i.e., patients aged 0-84), and no unexpected safety findings were observed. These findings demonstrate glucarpidase (50 U/kg) is an effective and well-tolerated dose for pediatric, adolescent, and young adult patients.

Oral Chemotherapeutic Ingestions Reported to a Poison Control Center Treated in a Health Care Facility

BACKGROUND

The approach to cancer chemotherapy has changed in recent years, and there are several new oral chemotherapeutics that offer convenience to patients. These medications have toxicity, which may be particularly amplified in an overdose.

STUDY DESIGN

This was a retrospective review of all oral chemotherapy overdoses reported to the California Poison Control System between January 2009 and December 2019. Inclusion criteria were all ingestions coded as "antineoplastic, monoclonal antibody, or thalidomide" that were evaluated at a health care facility. We evaluated outcomes per AAPCC criteria (stratified as death, major, moderate, mild, or no effect) as well as symptoms and interventions.

RESULTS

There were 314 total cases reported; 169 single-substance ingestions (54%) and 145 cases with coingestant(s) (46%). One hundred eighty cases were female (57%) and 134 male (43%). Age ranges were as follows: ages 1-10 years old (87 cases); ages 11-19 years old (26 cases); 20-59 years old (103 cases); ages 60 and older (98 cases). The majority of cases were unintentional ingestions (199, 63%). The most common medication reported was methotrexate with 140 cases (45%), followed by anastrozole (32 cases) and azathioprine (25 cases). One hundred thirty-eight cases were admitted to the hospital for further care (ICU 63 cases; non-ICU 75 cases). Eighty-four of the methotrexate cases received the antidote leucovorin (60%). Five of the capecitabine ingestions received uridine (36%). Outcomes included 124 cases with no effect, 87 cases with minor effect, 73 case with moderate effect, 26 cases with major effect, and 4 deaths.

CONCLUSION

Although methotrexate is the most common oral chemotherapeutic agent involved in overdoses reported to the California Poison Control System, there are many other oral chemotherapeutics from various drug classes, which can lead to toxicity. Although deaths are rare, further studies are needed to determine if particular drugs or drug classes warrant more scrutiny.

Peptide-drug conjugates (PDCs): a novel trend of research and development on targeted therapy, hype or hope?

Peptide-drug conjugates (PDCs) are the next generation of targeted therapeutics drug after antibody-drug conjugates (ADCs), with the core benefits of enhanced cellular permeability and improved drug selectivity. Two drugs are now approved for market by US Food and Drug Administration (FDA), and in the last two years, the pharmaceutical companies have been developing PDCs as targeted therapeutic candidates for cancer, coronavirus disease 2019 (COVID-19), metabolic diseases, and so on. The therapeutic benefits of PDCs are significant, but poor stability, low bioactivity, long research and development time, and slow clinical development process as therapeutic agents of PDC, how can we design PDCs more effectively and what is the future direction of PDCs? This review summarises the components and functions of PDCs for therapeutic, from drug target screening and PDC design improvement strategies to clinical applications to improve the permeability, targeting, and stability of the various components of PDCs. This holds great promise for the future of PDCs, such as bicyclic peptide‒toxin coupling or supramolecular nanostructures for peptide-conjugated drugs. The mode of drug delivery is determined according to the PDC design and current clinical trials are summarised. The way is shown for future PDC development.

Methotrexate and Triptolide regulate Notch signaling pathway by targeting the Nedd4-Numb axis

Methotrexate (MTX) is used to treat rheumatoid arthritis, acute leukemia, and psoriasis. MTX can cause certain side effects, such as myelosuppression, while the exact mechanism of myelosuppression caused by MTX is unknown. Notch signaling pathway has been considered to be essential to regulate hematopoietic stem cell (HSC) regeneration and homeostasis, thus contributing to bone marrow hematopoiesis. However, whether MTX affects Notch signaling remains unexplored. Here, our study provides evidence that MTX strongly suppresses the Notch signaling pathway. We found that MTX inhibited the interaction between Nedd4 with Numb, thus restricting K48-linked polyubiquitination of Numb and stabilizing Numb proteins. This in turn inhibited the Notch signaling pathway by reducing Notch1 protein levels. Interestingly, we found that a monomeric drug, Triptolide, is capable of alleviating the inhibitory effect of MTX on Notch signaling pathway. This study promotes our understanding of MTX-mediated regulation of Notch signaling and could provide ideas to alleviate MTX-induced myelosuppression.

Toxicological Aspects of Methotrexate Intoxication: Concentrations in Postmortem Biological Samples and Autopsy Findings

The aim of this study was the establishment of a UHPLC-QqQ-MS/MS method to determine methotrexate in postmortem biological samples and quantify the postmortem distribution of methotrexate in a case of fatal intoxication of this drug. A volume of 100 μL or 100 mg of postmortem specimens was precipitated with 400 μL of cold methanol and then analyzed using UHPLC-QqQ-MS/MS. The validation parameters of the method were as follows: limit of quantification: 0.1−1.0 ng/mL or ng/g, coefficient of determination: >0.998 (R2), matrix effect, intra- and inter-day accuracies and precisions: not greater than 13.6%, 14.8% and 17.4%, respectively. The recoveries were: 89.0−113.6%. The postmortem distribution studies revealed methotrexate concentrations as follows: blood—7.2 ng/mL, vitreous humor—0.8 ng/mL, liver—43.7 ng/g, kidney—20.6 ng/g, bone marrow—29.9 ng/g, lumbar vertebra—20.0 ng/g. The highest concentrations of methotrexate after poisoning were found in the tissues with the most rapidly dividing cells. The method described is simple, precise and selective. Methotrexate concentrations can be routinely determined in postmortem specimens. Determination of methotrexate in the postmortem biological material is possible after a few days of intensive treatment.

Availability of Antidotes for Management of Acute Toxicity Cases at Emergency Departments in Qassim Hospitals: A Retrospective Study

Background: Drug overdose is a medico-social issue worldwide that may occur intentionally or unintentionally. It is one of the most common reasons for emergency department visits, and it is also a frequent cause of morbidity and mortality globally. This study aims to determine the occurrence of acute toxicity cases and their management outcomes at the emergency departments in Qassim Province hospitals in Saudi Arabia. In addition, the study aims to investigate the antidote availabilities at those medical centers.

Methods: A retrospective hospital record-based study of acute toxicity cases admitted to the emergency department in hospitals in Qassim during the period from January 1, 2020, to December 31, 2020, was conducted. Data were collected based on hospital resources such as gastrointestinal decontamination, stabilization, elimination enhancement resources, and antidotes from Qassim hospitals, and the availability of antidotes as well as the clinical data of the patients with the management outcome.

Results: A total of 264 patients with acute toxicity were admitted to the emergency departments of 14 hospitals in Qassim Province in 2020. Of the 264 cases, 179 (68%) were males, and 85 (32%) cases were females. Ninety-five percent of the cases were admitted to public hospitals, whereas 5% were admitted to private hospitals. The largest group by age of admitted cases were aged 11-20 years (19.3%). This study showed that 99% received appropriate treatment for their cause of toxicity, whereas 1% did not. The most common causes of toxicity in Qassim were found to be food poisoning (20.5%), followed by intentional suicide attempts with warfarin/enoxaparin/aspirin overdoses (15.9%) and acetaminophen (paracetamol) overdosage seen in 15.5% of admitted cases. Flagyl, in addition to fluids, was used in the management of 16.7% of cases, N-acetyl cysteine was used for 16.3%, and vitamins K and B6 were used for 14.0% of cases. Activated charcoal, atropine, calcium chloride, calcium gluconate, flumazenil, insulin, magnesium, sodium bicarbonate, and vitamin K were available at all the studied hospitals. However, all the hospitals lacked both ethylenediaminetetraacetic acid (EDTA) and a cyanide kit. Methylene blue and leucovorin were available in only one of the studied hospitals.

Methotrexate Pneumonitis After a Low-Dose Medication Error: A Case Report

Methotrexate is recommended as the first choice of standard drug therapy following the diagnosis of rheumatoid arthritis. Pneumonitis related to methotrexate is a serious, unpredictable adverse event that may become life-threatening. We reported a case of a 68-year-old woman with rheumatoid arthritis that misunderstood the directions for use and took methotrexate daily, instead of weekly, leading to hepatic, hematological, and pulmonary toxicity.Although the histological evaluation was not performed, patient’s clinical presentation, in addition to subsequent investigational findings, supported a diagnosis of pneumonitis resulting from MTX exposure. Toxic dosing over a long period of time along with the concomitant taking of pantoprazole and hypoalbuminemia could have increased the incidence of some adverse events. Concerning pneumonitis related to methotrexate, the toxic dose may have accelerated the pulmonary manifestations, but we do not know if correct dose had been taken, this adverse event would occur. This case enlightened two important issues in rheumatoid arthritis treatment: the possibility of medication errors and the rare, but potentially life-threatening, methotrexate-induced pneumonitis. Improving education and warnings when prescribing and dispensing low-dose methotrexate is essential.

Extracorporeal Treatment for Methotrexate Poisoning: Systematic Review and Recommendations from the EXTRIP Workgroup

Methotrexate is used in the treatment of many malignancies, rheumatological diseases, and inflammatory bowel disease. Toxicity from use is associated with severe morbidity and mortality. Rescue treatments include intravenous hydration, folinic acid, and, in some centers, glucarpidase. We conducted systematic reviews of the literature following published EXtracorporeal TReatments In Poisoning (EXTRIP) methods to determine the utility of extracorporeal treatments in the management of methotrexate toxicity. The quality of the evidence and the strength of recommendations (either "strong" or "weak/conditional") were graded according to the GRADE approach. A formal voting process using a modified Delphi method assessed the level of agreement between panelists on the final recommendations. A total of 92 articles met inclusion criteria. Toxicokinetic data were available on 90 patients (89 with impaired kidney function). Methotrexate was considered to be moderately dialyzable by intermittent hemodialysis. Data were available for clinical analysis on 109 patients (high-dose methotrexate [>0.5 g/m²]: 91 patients; low-dose [≤0.5 g/m²]: 18). Overall mortality in these publications was 19.5% and 26.7% in those with high-dose and low-dose methotrexate-related toxicity, respectively. Although one observational study reported lower mortality in patients treated with glucarpidase compared with those treated with hemodialysis, there were important limitations in the study. For patients with severe methotrexate toxicity receiving standard care, the EXTRIP workgroup: (1) suggested against extracorporeal treatments when glucarpidase is not administered; (2) recommended against extracorporeal treatments when glucarpidase is administered; and (3) recommended against extracorporeal treatments instead of administering glucarpidase. The quality of evidence for these recommendations was very low. Rationales for these recommendations included: (1) extracorporeal treatments mainly remove drugs in the intravascular compartment, whereas methotrexate rapidly distributes into cells; (2) extracorporeal treatments remove folinic acid; (3) in rare cases where fast removal of methotrexate is required, glucarpidase will outperform any extracorporeal treatment; and (4) extracorporeal treatments do not appear to reduce the incidence and magnitude of methotrexate toxicity.

Poisoning related to therapeutic error in prolonged low-dose methotrexate treatment

AIMS

To study the predictive factors for the development of clinical manifestations in poisoning due to the erroneous taking of low-dose methotrexate (MTX).

METHODS

A retrospective observational study was performed. Only cases of erroneous administration in non-oncologic outpatients were included (July 2008-March 2020).

RESULTS

Forty-one cases were included. All patients were taking MTX for the first time. In 36 cases, patients took MTX daily instead of weekly. In the other five patients, MTX was sold instead of methylergometrine. Clinical manifestations were absent in 12/41 patients (29.3%). All 29 (70.7%) symptomatic patients recognized the medication error when they developed clinical manifestations: dermatological, haematological and gastrointestinal symptoms. Statistical results showed that symptomatic patients were older, received a higher amount of total dose and were treated for longer. Moreover, the probability of being symptomatic increases as a function of age and of total dose. Asymptomatic patients were treated with folinic acid (30 mg/m² /day) for 5 days. Symptomatic patients were treated with folinic acid together with treatments for the specific clinical manifestations. No patients were treated with glucarpidase. All patients fully recovered.

CONCLUSIONS

When MTX is prescribed for the first time, it is important to clearly communicate with patients to avoid therapeutic errors. In our experience, age, total dose taken and number of days of assumption are predictive for the presence/absence of clinical manifestations. These parameters must be evaluated together to identify patients needing maximum starting treatment with folinic acid and closer monitoring.

Methotrexate overdose in clinical practice

BACKGROUND

A folic-acid antagonist, methotrexate, is one of the most commonly prescribed drugs with its expanding use in clinical practice. The drug requires regular monitoring given its wide range of adverse effects including bone marrow suppression, hepatic or renal dysfunction, gastrointestinal distress, mucocutaneous damage, and neurotoxicity. The toxicity usually occurs rapidly and leads to severe neutropenia, sepsis, and advanced renal failure that are difficult to manage.

METHODS

This review is an update for the clinicians to understand the pharmacology, clinical features, laboratory evaluation, and treatment of patients with methotrexate overdose. High-quality literature of the past six decades was collected and reviewed in this article. Several landmark articles were reviewed using PubMed, EMBASE Ovid, and the Cochrane Library, that have important implications in current clinical practice.

RESULTS

Methotrexate overdose has complex toxicokinetic and produces myriad clinical features mimicking conditions of lesser severity. Organ dysfunction related to bone marrow, kidney or central nervous system is lifethreatening. The management should focus on high-quality supportive care, antidotal therapy (folinic acid and carboxypeptidase- G2) and plasma alkalization.

CONCLUSION

In accordance with the dictum "prevention is better than cure", the author emphasizes on the role of patient education, regular clinical observation, and laboratory monitoring for prompt recognition and diagnosis of methotrexate overdosing at the earliest stage.

Cytopenia induced by low-dose methotrexate: An analysis of 433 cases from the French pharmacovigilance database

INTRODUCTION

Up to 5% of individuals exposed to low-dose methotrexate (MTX) (i.e., ≤30 mg/week) may develop cytopenia. However, MTX-induced cytopenia have been poorly described.

MATERIAL AND METHODS

All cases of cytopenia (i.e., anaemia, leukopenia, thrombocytopenia, bi- or pancytopenia) in patients receiving low-dose MTX reported to the French pharmacovigilance database during 2006-2016 were analysed. Three groups were defined: cytopenia due to MTX medication errors (e.g., daily rather than weekly administration), cytopenia in people receiving several medications including MTX, cytopenia in people receiving only MTX.

RESULTS

433 cases were analysed. Eighty-four cases (19.4%) were due to medication errors, 180 (41.6%) occurred in individuals exposed both to MTX and other drugs, and 169 (39.0%) occurred in individuals only exposed to MTX. By comparison to other patients, those with cytopenia due to medication errors were older (74 ± 13 vs 69 ± 15 years, p = 0.002), received more frequently MTX orally (92.9% vs 65.3%, p<0.001) and had more frequently pancytopenia (71.4% vs 54.4%, p = 0.005). By comparison to individuals exposed to multiple drugs (n = 180), those exposed only to MTX (n = 169) were older (71 ± 15 vs 67 ± 14, p = 0.02), and had more often pancytopenia (62.7% vs 46.7%, p = 0.001). Among those only exposed to MTX, most cases (n = 140, 82.8%) were considered as toxic rather than idiosyncratic reactions and a trigger (e.g. diarrhoea) was found in 59.3% of those cases. Overall 30 (6.9%) deaths occurred, including 8 in the "medication error" group and 8 in the "MTX only" group.

CONCLUSION

These data may be useful for defining optimal biological monitoring of patients prescribed low-dose MTX.

Development of an algorithm to detect methotrexate wrong frequency error using computerized health care data

PURPOSE

We validated an algorithm to detect frequency errors in computerized healthcare data and estimated the incidence of these errors in an integrated healthcare system.

METHODS

We applied Sentinel System analytic tools on the electronic health records of Kaiser Permanente, Northern California, January 1, 2010, through May 30, 2015,to identify rheumatoid arthritis (RA) patients with new use of methotrexate (365-day baseline period). We identified potential methotrexate frequency errors using ICD-9 code 995.20 (adverse drug event), Current Procedural Terminology (CPT) code 96409 for injection of leucovorin and prescription refill patterns. We performed chart review to confirm the frequency errors, assessed performance for detecting frequency errors, and estimated the incidence of chart-confirmed errors.

RESULTS

The study included 24,529 methotrexate dispensings among 3,668 RA patients. Among these, 722 (3%) had one dispensing and 23,807 (97.1%) had ≥2 dispensings during 1-year follow-up period. We flagged 653 (2.7%) with a potential medication error (46 with one dispensing and 607 with ≥2 dispensings). We sampled 94 for chart review, and confirmed three methotrexate errors. All three confirmed frequency errors involved a first methotrexate dispensing followed by injected rescue therapy, leucovorin, (positive predictive value, 60%; 95% confidence interval [CI], 15-95%). No potential errors were found among patients with ≥2 dispensings. We estimated the frequency error incidence among one methotrexate dispensing to be 0.4% (95%CI, 0.1% to 1.2%).

CONCLUSION

Rescue therapy is a specific indicator of methotrexate overdose among first methotrexate dispensings. This method is generalizable to other medications with serious adverse events treated with antidotes.

Acute versus chronic methotrexate poisoning; a cross-sectional study

Background

Data is limited on comparison of acute and chronic methotrexate (MTX) poisoning. Methotrexate is an anti-folate drug that may be prescribed in some malignant or chronic inflammatory conditions. The aim of the current study was to compare signs and symptoms, complications, treatment and final outcome of acute and chronic MTX toxicity.

Method

In a retrospective study in a referral center between March 2010 and March 2018, all patients who had been referred with the history of MTX poisoning and hospitalized due to acute or chronic poisoning were evaluated and compared.

Results

Of the total 27 patients admitted during the study period, 13 had referred with acute (group 1; consumption of MTX for less than 7 days) and 14 had referred with chronic toxicity (group 2; consumption of MTX for more than 7 days). Mean age was significantly higher in the second group (P < 0.001). Median total dose of MTX was similar between the groups (P = 0.90). Mucosal ulcers and skin lesions (P < 0.001 and 0.02, respectively) were the only symptoms significantly different between the two groups. Leukopenia (P < 0.001), thrombocytopenia (P < 0.001), and anemia (P = 0.04) were significantly more common in the second group. Blood urea nitrogen and creatinine were also significantly higher in the second group of the patients (P < 0.001 and P = 0.048). Median leucovorin administered dose was 200 mg [14, 480] versus 150 mg [75, 187] (P = 0.69) in groups 1 and 2, respectively.

Conclusions

Chronic MTX poisoning is more serious than acute toxicity and accompanies higher dermatologic, hematologic, and hepatic complications necessitating more aggressive treatments including administration of higher doses of leucovorin or bone marrow stimulants such as G-CSF. This may be attributable to the underlying diseases and features (including older ages) which predispose these patients to complications.

Construction of Persistent Luminescence-Plastic Antibody Hybrid Nanoprobe for In Vivo Recognition and Clearance of Pesticide Using Background-Free Nanobioimaging

We prepared a specific adsorptive nanocarrier for pesticide due to its challenge to cleanup and low detoxification in the treatment after intake, whether intentional or by mistake. We modified the plastic antibody (molecularly imprinted polymer (MIP)) on the surface of persistent luminescence nanoparticle (La₃Ga₅GeO₁₄: Cr³⁺, Zn²⁺, LGGO) as the specific adsorptive nanocarrier for toxic molecules and realized the nanocarrier was widely distributed for absorbing pesticide and real-time in vivo bioimaging. We used LGGO as the core and trichlorphon as the template to prepare the plastic antibody nanocarrier. After in vivo bioimaging and biodistribution of mice, LGGO@MIP could be distributed evenly in the gastrointestinal tract, circulated in the blood for a long time, and finally excreted to achieve the adsorption and removal of pesticide in the body. The LGGO@MIP nanocarrier prepared in this study opens a new way for the treatment of poisoning.

Adverse consequences of low-dose methotrexate medication errors: data from French poison control and pharmacovigilance centers

OBJECTIVE

The objectives of this study are to carefully describe the context of methotrexate medication errors, to details medical consequences and management approaches, and to determine the rate of fatal outcome.

METHODS

Data on methotrexate medication errors were obtained from the French network of poison control and pharmacovigilance centres, which collected and documented reported drug-induced adverse effects. Cases were included if the intake was more than 2-fold the intended weekly dose or a weekly cumulative dose ≥ 30 mg and a follow-up of at least 4 days after the last dose. Data were analysed for demographics, treatment indication, prescribed dose, drug interactions, clinical complications and medical outcomes.

RESULTS

Seventy four patients were included. The causes of methotrexate errors resulted from an erroneous prescription renewal (23.3%), incomprehensiveness of the weekly schedule by patients or at-home caregivers (56.2%) and administration of a wrong dose by a health care professional (20.5%). Of the 70 patients who took methotrexate daily, the mean daily dose received over the whole duration of the error was 9.6 ± 4.1 mg (range 2.5-22.5) with a mean duration of the error of 11.7 ± 12.2 days (range 2 to 90). Thirteen (18%) patients remained asymptomatic and 61 (82%) developed complications of which 46 (62.2%) were severe. Nine (14.8%) patients died within 11 to 45 days after the first dosing error. Compared to patients with no or mild symptoms, those with severe symptoms were more likely to be older (75.6 ± 10.8 vs. 69.5 ± 12.9 years) and to be exposed to a higher cumulative dose (94.8 ± 46.2 vs. 68.0 ± 45.7 mg).

CONCLUSIONS

This study confirms that dosing errors with methotrexate can be lethal and persisted despite several warnings from drug agencies. Further measures are awaited from the European Medicine Agency.

Medication Error- A Case Report of Misadventure with Methotrexate

Methotrexate is an antimetabolite drug with antineoplastic and immunomodulatory properties, useful as an antineoplastic agent in various haematological and solid tumours. MTX toxicity can occur because of accidental ingestion/overdose by the patient or because of prescription error. The toxic effects manifest as severe mucositis or as organ damage (bone marrow depression, renal/hepatic injury). The toxicity usually results from parenteral overdose or repeated chronic drug ingestion. Acute high dose ingestion does not result in MTX toxicity because of saturable absorption kinetics. We present a case of MTX toxicity occurring as a result of prescription error resulting in repeat daily dosing of the drug, and the challenges associated with the management of the same, in a patient with multiple comorbidities. The present case emphasizes on a note of caution on the part of the prescriber and the suggestions regarding the measures which can be taken to avoid MTX toxicity. Keywords: drug overdose; Methotrexate; mucositis; pancytopenia.