Pharmacokinetics and efficacy of digoxin specific Fab fragments in a child following massive digoxin overdose

Detecting the therapeutic drugs in blood samples through PDMS-printed paper spray mass spectrometry

In this paper, paper microfluidic channel fabricated by directly screen-printing of polydimethylsiloxane (PDMS) is proposed for paper spray mass spectrometry analysis of therapeutic drugs in the blood samples. Compared with traditional paper spray, PDMS-printed paper spray (PP-PS) allows fluid to flow to the tip of paper with less sample loss which significantly improved the signal intensity of target compounds in blood samples. As paper can reduce the matrix effect, PP-PS also has a greater advantage than electro-spray Ionization (ESI) when directly analyzing complex biological sample in terms of the detection efficiency. Linearity and limits of detection (LOD) were evaluated for five psychotropic drugs: olanzapine, quetiapine, 9-hydroxyrisperidone, clozapine, risperidone. As a result, PP-PS improved the signal intensity of the psychotropic drugs at a concentration of 250 ng/ml in blood samples by a factor of 2-5 times and lowered the relative standard deviation (RSD) by a factor of 2-5.6 times compared with traditional paper spray. And PP-PS also improved signal intensity by a factor of 9-33 times compared with ESI. Quantitative experiments of PP-PS mass spectrometry indicated that the linear range was 5-500 ng/ml and the LOD were improved by a factor of 5-71 times for all these drugs compared with traditional paper spray. In addition, PP-PS was applied to the home-made miniaturized mass spectrometer and the precursor ions of all five psychotropic drugs (250 ng/ml) in the mass spectrometry results were obtained as well. These could prove that PP-PS has the potential to analyze complex biological samples in application on the miniaturized mass spectrometer which can be used outside the laboratory.

Knowledge and Attitude of Healthcare Practitioners Toward Therapeutic Drug Monitoring Practices in the Najran Region, Kingdom of Saudi Arabia

BACKGROUND

Therapeutic drug monitoring (TDM) is one of the useful clinical tools that aim to improve and ensure the best therapeutic effects while avoiding drug-related toxicity. We aimed to evaluate the knowledge and attitude toward TDM practices among healthcare practitioners in the Najran region, Saudi Arabia.

METHODOLOGY

A cross-sectional study was conducted between May 2021 and October 2021 for assessing the awareness and attitude of licensed doctors and pharmacists working in Saudi Arabia regarding TDM practices. A 31-item questionnaire was distributed to the healthcare professionals via an electronic link. Descriptive and inferential statistics were used to report the data.

RESULTS

A total of 392 participants submitted questionnaires. More than half of the professionals (55.9%) had an overall awareness of the TDM, while only 3.1% did not. Only 16% and 23% of those who were surveyed indicated that TDM is used at the beginning of medication administration and when shifting from one drug to another, respectively. The majority of the professionals responded that TDM is revealed with laboratory changes in liver and kidney function (81%), and TDM is specified with suspected therapeutic failure (93%). Only half of the respondents claimed that they had ever requested or suggested a TDM in their practice. More than 90% of the respondents claimed that they were aware of the indications for vancomycin (n = 381), gentamicin (n = 375), lithium (n = 369), digoxin (n = 380), and theophylline (n = 369).

CONCLUSION

This study found that the majority of the healthcare professionals in Najran were aware of the TDM, particularly those with more than 10 years of professional experience. In addition, TDM service is not widely available in smaller hospitals in Najran. There is a need to conduct customized training programs for junior healthcare professionals, thus increasing the levels of awareness toward TDM. Future studies in Saudi Arabia can explore the role of clinical pharmacists in the provision of TDM services by assessing the clinical and economic outcomes of pharmacist interventions in TDM.

Overview of therapeutic drug monitoring

Therapeutic drug monitoring (TDM) is the clinical practice of measuring specific drugs at designated intervals to maintain a constant concentration in a patient's bloodstream, thereby optimizing individual dosage regimens. It is unnecessary to employ TDM for the majority of medications, and it is used mainly for monitoring drugs with narrow therapeutic ranges, drugs with marked pharmacokinetic variability, medications for which target concentrations are difficult to monitor, and drugs known to cause therapeutic and adverse effects. The process of TDM is predicated on the assumption that there is a definable relationship between dose and plasma or blood drug concentration, and between concentration and therapeutic effects. TDM begins when the drug is first prescribed, and involves determining an initial dosage regimen appropriate for the clinical condition and such patient characteristics as age, weight, organ function, and concomitant drug therapy. When interpreting concentration measurements, factors that need to be considered include the sampling time in relation to drug dose, dosage history, patient response, and the desired medicinal targets. The goal of TDM is to use appropriate concentrations of difficult-to-manage medications to optimize clinical outcomes in patients in various clinical situations.

The use of digoxin-specific Fab fragments for severe digitalis intoxication in children

BACKGROUND

Because life-threatening digitalis intoxication is unusual in children, treatment with digoxin-specific-antibody Fab fragments (Fab) has rarely been reported. We describe the efficacy of Fab in the treatment of children with severe digitalis intoxication.

METHODS

Twenty-nine children with intoxication due to digoxin (28) or digitoxin (1) received Fab at 21 participating hospitals between 1974 and 1986. Data were gathered about the patients' medical illnesses, doses and serum concentrations of digitalis, responses to Fab therapy, and outcomes.

RESULTS

In the infants and young children with acute digoxin intoxication, the digoxin doses ranged from 0.30 to 0.96 mg per kilogram of body weight; two adolescents had severe intoxication after doses of only 0.20 and 0.26 mg per kilogram. The serum digoxin concentrations ranged from 3.0 to greater than 100 ng per milliliter (mean, 13.8). Atrioventricular block (present in 22 patients [76 percent]) was the most common sign of toxicity. All the patients in this series had severe disturbances of cardiac rhythm, hyperkalemia (mean serum potassium concentration, 5.4 mmol per liter), or both. In 27 patients (93 percent), digitalis toxicity resolved after the administration of Fab. Of the 19 patients for whom data were available on the timing of the response to Fab, 15 responded within 180 minutes. Three patients required retreatment with Fab. Seven died of complications unrelated to the administration of Fab.

CONCLUSIONS

We recommend that Fab be used in the treatment of digitalis poisoning in infants and young children who have ingested greater than or equal to 0.3 mg of digoxin per kilogram, who have underlying heart disease, or who have a serum digoxin concentration of greater than or equal to 6.4 nmol per liter (greater than or equal to 5.0 ng per milliliter) in the elimination phase; and who also have a life-threatening arrhythmia, hemodynamic instability, hyperkalemia, or rapidly progressive toxicity. Adolescents, who are more sensitive to the toxic effects of digoxin than younger children, may require treatment with Fab after ingesting lower doses.

Age-related differences in digoxin toxicity and its treatment

Digoxin toxicity remains a common medical problem for both adults and children. In addition to a vastly improved understanding of the mechanisms for digoxin action on the heart, there are now data which clearly demonstrate that there are potentially important developmental differences in both the pharmacodynamics and pharmacokinetics of digoxin which have a direct impact on its efficacy and toxicity profile. The developmental pharmacokinetics of the drug have been extensively studied such that profiles for age-dependent differences in the apparent volume of distribution, plasma and renal clearance and elimination half-life now exist. It is these data which have also produced the current age-specific dosing guidelines for the therapeutic administration of digoxin in various paediatric subpopulations. Despite this new knowledge, both accidental and iatrogenic digoxin toxicity still occurs in paediatric patients, with potentially life-threatening arrhythmias being produced when steady-state serum digoxin concentrations exceed 5.1 nmol/L. Consequently, the clinician may be faced with the decision to use antidotal therapy with digoxin-specific Fab fragments (d-Fab). This article reviews the developmental basis for digoxin disposition and its pharmacological and toxic effects. Additionally, the treatment of acute digoxin toxicity in children is reviewed, especially as pertains to the therapeutic use of d-Fab.

Results of multicenter studies of digoxin-specific antibody fragments in managing digitalis intoxication in the pediatric population

Digitalis toxicity continues to be a problem for pediatric patients undergoing therapy with cardiac glycosides for heart failure or arrhythmias, as well as in accidental ingestions. In this article the previous use of digoxin-specific antibody Fab fragments to treat digitalis overdose or intoxication in children is reviewed. The case reports cited in the medical literature and the 57 pediatric cases gathered as a result of the multicenter clinical trial and postmarketing surveillance study reported here indicate that digoxin-specific antibody Fab fragments are effective in ameliorating signs of digitalis poisoning in children. Not only can Fab fragments rapidly eradicate potentially life-threatening arrhythmias and conduction defects, but they are also effective in treating hyperkalemia and other noncardiac manifestations of digitalis toxicity. In the small samples of patients studied to date, complications have been minimal and no allergic reactions to digoxin-specific Fab fragments have been observed. Recommendations for the management of digitalis intoxication in children are outlined.