Author(s)

Wei Wang, Hao Bai

Why was it done?

It depend on the pharmacokinetic (PK)/pharmacodynamic (PD) of vancomycin. Vancomycin can be described as a kinetic model with one compartment connected by a series of first-order kinetic rate processes. The mini programme uses two drug levels during the same dosing interval by the TDM to calculate the area under the curve (AUC) of vancomycin and integrated into patients’ condition and minimal inhibitory concentration of pathogen to provide an optimal dosing regimen of vancomycin.

What was done?

We designed and developed a mini programme support for personalised therapeutic drug monitoring (TDM) of vancomycin. This programme can be easily used in the WeChat by the mobile device.

How was it done?

The traditional vancomycin TDM strategy, which is guided by trough concentrations, has several limitations:
The recommended trough concentration range of 10-15mg/L assumes that the bacteria’s minimum inhibitory concentration (MIC) for vancomycin is ≤1mg/L. However, with the drifting of vancomycin’s MIC values over recent years, this trough concentration has not been able to effectively guide patient prognosis, as has been confirmed by many clinical studies.
There are practical difficulties: for example, the 2009 IDSA guidelines clearly specify that the trough concentration of vancomycin should be sampled half an hour before the fifth dose. However, in reality, due to misunderstandings by nursing staff or excessive workload, sampling times often deviate from this guideline.
After the trough concentration has been determined, there are no explicit measures for dose adjustment. The 2009 IDSA guidelines do not provide recommendations on how to adjust subsequent doses based on trough concentrations.
A decade later, in 2020, the IDSA released new vancomycin TDM guidelines. These guidelines suggest moving away from the trough concentration TDM strategy for vancomycin, and instead recommend using an AUC-guided strategy, determined by two-point blood concentration monitoring of vancomycin.

What has been achieved?

Vancomycin follows first-order pharmacokinetics. To monitor the AUC of vancomycin, it is necessary to measure the serum vancomycin concentration at two steady-state points, then use Monte Carlo simulations and Bayesian software to calculate the AUC and adjust the dosage. This process requires a large number of calculations. Therefore, there is an urgent need for an auxiliary decision making system in clinical practice that can facilitate personalised dosing of vancomycin.

What next?

This mini programme has run above 1 year, providing personalised medicine service of vancomycin to hundreds of patients in China, guiding the precise and rational use of antimicrobial drugs , enhancing the effectiveness of vancomycin and reducing drug toxicity in clinical practice.

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Author(s)

Alba María Fernández Varela, María Isaura Pedreira Vázquez, Sandra Koprivnik, Ana María Montero Hernández, Isaura Rodríguez Penín

Why was it done?

Therapeutic drug monitoring (TDM) allows an optimised pharmacological treatment and increases safety. Lately, we detected low interest in TDM which was confirmed from our annual activity report. An observational prospective study was carried out in a second- level hospital attending an area of 175 930 patients. The study included all inpatients prescribed a drug eligible for TDM from November 2020 to January 2021. The aim was to improve treatment individualisation of hospitalised patients through an active proposal for drug level determination of drugs susceptible for TDM at our institution: digoxin, vancomycin, antiepileptic drugs (carbamazepine, phenytoin, phenobarbital and valproic acid).

What was done?

The pharmacist encouraged therapeutic drug monitoring of susceptible treatments by an active proposal for drug level determination in the prescriptions programme.

How was it done?

Daily, a list of eligible patients was obtained. To this end, a filtering software was used. Taking into account patient’s demographics, clinical and analytical variables (creatinine clearance, the last TDM result, diagnosis) and active prescriptions (treatment initiation, interactions), the pharmacist makes a recommendation for plasma drug level determination.
Data sources: electronic prescription program, pharmacokinetic validation program and electronic medical record.

What has been achieved?

119 proposals of TDM were made in 107 patients: 79 digoxin, 31 vancomycin, 4 valproic acid, 3 carbamazepine and 2 phenytoin. 45,8% women.
74 drugs were discontinued before possible sample extraction and 5 monitorisations could not be performed due to patient death. Of the 40 remaining proposals, the physician requested monitoring of 35 drugs, which meant 87,5% acceptance rate.
It was observed that 17 levels were low or at a lower limit (a dose increase with subsequent verification of levels was proposed in 8 cases and accepted in all of them), 13 levels were in range, 4 were high or at an upper limit (in 3 of them the dose was decreased). One sample was extracted after the drug administration (vancomycin) therefore without value.

What next?

Pharmacists can contribute to treatment optimisation by being proactive. Many resources are not needed unless the burden of care was a limiting factor. The education and promotion of TDM would be interesting to improve the use of this service.

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Author(s)

María Calvo Arbeloa, Ana Isabel Idoate Grijalba, Mónica Uxue Beunza Sola, Daniel Fresán Restituto, Regina Juanbeltz Zurbano, Diana Tejada Marín , Andrea Rodriguez Esquiroz, Maite Sarobe Carricas

Why was it done?

Patients with special characteristics show a great variability in pharmacokinetic and pharmacodynamics (PK/PD) parameters, which may influence the efficacy and safety of antibiotic therapy.

What was done?

A Clinical Unit of Pharmacokinetics was implemented in the Service of Pharmacy (PS) for therapeutic drug monitoring (TDM) in patients.

How was it done?

1. Selection of drugs to be monitored: Antimicrobials (Vancomycin, amikacin, linezolid and voriconazole), Immunosuppressants (tacrolimus), Antineoplastics (methotrexate) and digoxin.
2. Installation of the Abbottbase Pharmacokinetic System (Pks®) software.
3. Creation in the Computerised Clinical History (CCH) a sheet for collecting anthropometric and pharmacological data and pharmacokinetic interpretation of the results obtained.
4. Creation in CCH of a consultation option for clinicians to request monitoring from the PS.
5. Formative session for clinicians and nurses.

What has been achieved?

To begin with the unit, we selected three drugs: vancomycin, amikacin and voriconazole. The hospital pharmacist or the clinician chose the susceptible patients.
Between December 2021 and September 2022, 171 determinations were made in 73 patients: 134 (78.36%) for vancomycin, 24 (14.06%) for amikacin and 13 (7.60%) for voriconazole. Forty-six (63.01%) patients were men and the mean age was 56.58 (17-97) years- old. Eighteen (24.66%) patients were obese. The mean creatinine level was 0.82 (0.4-2.69) mg/ml and glomerular filtration according to the Cockcroft and Gault formula was 81.16 (23.68-161.98) ml/min/m².
For vancomycin, 45 (88.24%) patients started the treatment with a standard dose of 1000 mg every 12 hours. In first determinations, 27 (52.94%) were under-therapeutic and 20 (42.55%) were overdosed. After modifying the dosage regimen, 35 (74.47%) were in range, 3 (6.38%) under-therapeutic and 13 (27.66%) supra-therapeutic.
In case of amikacin, 17 (85%) patients started with a standard dose (1000 mg every 24 hours) achieving target levels only in one case. All were under-therapeutic. After modifying the dosage regimen, we achieved the objective in all of them.
For voriconazole 3 patients were monitored. In 10 (43.5%) determinations, a change in dosage regimen was suggested due to subtherapeutic levels. All (100%) of the recommendations given by the PS were accepted.

What next?

The implementation of the unit in our hospital shows the usefulness and the need to extend pharmacokinetic monitoring to other medical services and drugs.

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Author(s)

María Mar Alañón Pardo, Alejandro Marcos de La Torre, Beatriz Proy Vega, Adrián Pérez Facila, María Luisa Moreno Perulero, Clara Notario Dongil

Why was it done?

Numerous publications have demonstrated a correlation between serum concentrations (Cs) of anti-TNF drugs and the therapeutic response and a wide interindividual variability in pharmacokinetics among patients with IBD. TDM permits dosage individualization and optimization of anti-TNF therapy.

What was done?

Pharmacokinetic monitoring (TDM) of anti-TNF therapies (infliximab/adalimumab) in inflammatory bowel disease (IBD) was implemented in our hospital by a multidisciplinary team of pharmacists, gastroenterologists and clinical analysts.

How was it done?

A computer platform was developed within the hospital electronic records system to manage consultations of gastroenterologists with the Clinical Pharmacokinetics Unit (CPU) of the Pharmacy Department. Variables in this electronic interconsultation system were: “anti-TNF drug”, “concomitant immunomodulator (IMM)”, “diagnosis”, “reason for consultation”, “date of last dose”, “date of extraction”, “weight/height”, and “observations”. Laboratory tests ordered from the Department of Clinical Analysis on the electronic request form included blood count, Cs of infliximab/adalimumab, albumin, C-reactive protein and faecal calprotectin. Quantum Blue® lateral flow immunoassay was used to quantify Cs of the anti-TNF drugs; when undetectable, the presence of anti-drug antibodies (ADAs) was investigated.
The CPU developed pharmacotherapeutic recommendations based on therapeutic algorithms, pharmacokinetic/pharmacodynamic principles and population models implemented using MW-Pharm++® software, which incorporates the principle of Bayesian estimation. For a correct interpretation of the Cs observed, adherence to anti-TNF ± IMM regimens was evaluated using electronic dispensing records and the self-administered Morisky-Green questionnaire.

What has been achieved?

Since its implementation (January 2019 – August 2020), the CPU has responded to 269 consultations on 121 patients treated with infliximab (46.3%) or adalimumab (53.7%): 70.2% were prescribed with IMM (89.4% with thiopurines); 93.4% adhered to the anti-TNF regimen and 82.4% to the IMM. Baseline anti-TNF Cs were subtherapeutic in 37.2% of patients, therapeutic in 35.5% and supratherapeutic in 27.3%. ADAs were positive in 28.6% of patients with undetectable anti-TNF Cs (n=28). A large proportion (84.8%) of consultations were related to proactive monitoring (to optimise treatment) and the remainder were reactive (after treatment failure). A very high percentage (89.9%) of the gastroenterology specialists accepted recommendations.

What next?

Extend TDM to other biological therapies and immune-mediated diseases.

Author(s)

VERA DOMINGOS, VERA PIRES, SÍLVIA SANTOS, PATRÍCIA TRINDADE, ANA INÁCIO, ELZA CANDEIAS, SUSANA SIMÕES, PAULO PAIXÃO, NUNO MIRANDA, ANTÓNIO GOUVEIA

Why was it done?

Personalized BU dosing is considered because BU has a narrow therapeutic index and exposure have been associated with important clinical outcomes. High exposures have been associated with an increased risk of toxicities (acute graft-versus-host disease and veno-occlusive disease) and low exposures with graft rejection and relapse.
For this reason, in a multidisciplinary working group, we identified an opportunity to improve the treatment of your patients.

What was done?

Implementation of a TDM procedure for Busulfan (BU) in conditioning therapy for hematopoietic stem cell transplantation (HSCT). Study variability in PK parameters and evaluate TDM efficacy. From this initial period, we perform TDM on all patients under Bu conditioning.

How was it done?

The steps followed were:
1. Pre-implementation: bibliographic research, identify reference centers to perform BU plasma assay. Development and validation of a LC-MS / MS method by the National Institute of Forensic Medicine. PK analysis using ADAPT-5 software.
2. Pilot: Trial and assess the feasibility of the procedure. Cross-validation of the results with UMC Utrecht.
3. Implementation: clinical practice, doing the necessary dose adjustments. Prospective collection of clinical and PK data.

The main obstacle is the lack of analytical methodology in our center and the turnaround time.

What has been achieved?

We performed a preliminary analysis with 21 patients. Mean clearance (CL) was 0,19L/h*kg±0,05L/h*kg and volume of distribution 0,65L*kg±0,22L*kg. Body weight was the most predictive covariance.
CL was significantly different between patients 10 years old (p = 0,024) and over treatment (p=0,0191). The type of conditioning regimen didn’t show relation with the BU CL (p=0,0514).
TDM increased the number of patients with an optimal exposure (target AUC ±10%) from 42% to 83%.Dose was reduced in 10 patients (max 37%) and increased in 3 (max 19%). 1 patient maintained the prescribed dose.

What next?

TDM increased significantly the number of patients with optimal exposure to BU.
This procedure is pioneer at a national level and it relies on a strict protocol which includes collaboration with several hospital departments and other highly-specialized external centers. This can be used as a tool for other drugs and to empower the pharmacist as an active agent in the clinical setting.