Assessment of acyclovir intraindividual pharmacokinetic variability during continuous hemofiltration, continuous hemodiafiltration, and continuous hemodialysis

Pharmacokinetic profile of acyclovir in a child receiving continuous kidney replacement therapy for acute liver failure

BACKGROUND

Continuous venovenous hemodiafiltration (CVVHDF) is one of the treatments of critically ill children presenting severe acute liver failure. This affliction might be induced by HSV infection requiring a treatment by acyclovir. Continuous kidney replacement therapy (CKRT) can alter its pharmacokinetics, according to its physicochemical properties and CVVHDF settings.

CASE-DIAGNOSIS/TREATMENT

The patient was a 21-month-old female presenting liver failure with hyperammonemia treated by acyclovir with presumed HSV infection. CKRT was initiated on day 1 with substantial replacement and dialysate flow rates (respectively 75 and 220 mL/kg/h). Acyclovir was intravenously administered every 8 h with a 1-h infusion of 500 mg/m2. Plasma and effluent concentrations were measured by liquid chromatography-tandem mass spectrometry assay to estimate the area under a curve (AUC) and CKRT clearance by 2 methods (one based on pre- and post-filter concentrations and the other one on dialysate flow rates). Clearance was estimated between 19.2 and 26.3 mL/min with the first method and between 27.6 and 44.3 mL/min with the second one. Concentrations were highly above the therapeutic index (peak concentration was measured at 28 mg/L), but AUC was appropriate.

CONCLUSIONS

This case describes acyclovir pharmacokinetics during CKRT in a pediatric patient treated by acyclovir. The patient was treated with adapted exposure with the usual dosing, but lower dosing should be investigated with complementary studies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02539407.

[A Pharmacist's Query Avoiding Exacerbation of Adverse Effects in a Patient with Acyclovir Encephalopathy: A Case Report]

We report a haemodialysis patient with end-stage renal failure whom a pharmacist aided in the management of acyclovir (ACV) encephalopathy, which may have been related to valacyclovir hydrochloride (VACV) administered without sufficient dose reduction. The patient 78 years was admitted with a tentative diagnosis of varicella zoster viral meningitis. A pharmacist suspected ACV encephalopathy related to excessive VACV administration and raised a query with the attending physician. According to the pharmacist's proposal, ACV administration was discontinued and continuous hemodiafiltration (CHDF) was performed. On day 5 of hospitalisation, the consciousness disorder was improved. In this report, we showed the detailed CHDF conditions of the present case, and the contribution of a pharmacist to treating and avoiding ACV encephalopathy was discussed.

Valacyclovir Neurotoxicity and Nephrotoxicity in an Elderly Patient Complicated by Hyponatremia

A 66-year-old women with no history of renal disease was admitted due to a coma and acute kidney injury with a serum creatinine level of 7.44 mg/dL which were ascribed to valacyclovir neurotoxicity and nephrotoxicity, respectively. She had received valacyclovir at a standard dosage for the treatment of herpes zoster and was finally discharged, having fully returned to her normal baseline mental status with a recovered serum creatinine level of 0.68 mg/dL. We feel that awareness of this pathology remains a challenge for physicians and therefore strongly recommend the further accumulation of experiences similar to our own. Our experience underscores the pitfalls of administering valacyclovir to elderly patients who barely appear to have a favorable renal function. Several concerns regarding the therapeutic management, including blood purification strategies, that emerged in this case are also discussed.

Therapeutic Drug Monitoring in Neonatal HSV Infection on Continuous Renal Replacement Therapy

Optimal acyclovir dosing under continuous renal replacement therapy (CRRT) in neonates is unknown. We monitored serum acyclovir levels and herpes simplex virus 1 (HSV-1) DNA levels in a neonate with disseminated HSV-1 infection and renal failure undergoing CRRT. A full-term, 5-day-old female presented with a 2-day history of lethargy and fever. She developed fulminant hepatitis and was diagnosed with HSV-1 infection by real-time polymerase chain reaction. Acyclovir was initiated at 60 mg/kg/day, which was lowered to 20 mg/kg/day because of development of renal failure. She was placed on continuous hemodialysis. Acyclovir dosing was adjusted according to serum acyclovir levels, and HSV-1 viral load was sequentially monitored. Semiquantification of serum HSV-1 levels was performed by real-time polymerase chain reaction. Acyclovir levels were measured by using liquid chromatography-tandem mass spectrometry. Acyclovir was administered at 20 mg/kg intravenously over 1 hour; peak concentration was 18.9 μg/mL. The half-life of acyclovir was estimated to be 2 to 3 h. Viral load remained high during dosing every 24 hours, with a decline of 0.17 log copies/24 hours. Acyclovir dosing was changed to 20 mg/kg/dose every 8 hours, with an average viral load decline of 0.44 log copies/24 hours. Despite the guideline recommendation of 24-hour redosing, acyclovir was dialyzed at a rate that resulted in suboptimal treatment. Individual therapeutic drug monitoring for acyclovir and dosing adjustment may be required to optimize therapy for patients undergoing CRRT.

Presence and accuracy of drug dosage recommendations for continuous renal replacement therapy in tertiary drug information references

BACKGROUND

Clinicians commonly rely on tertiary drug information references to guide drug dosages for patients who are receiving continuous renal replacement therapy (CRRT). It is unknown whether the dosage recommendations in these frequently used references reflect the most current evidence.

OBJECTIVE

To determine the presence and accuracy of drug dosage recommendations for patients undergoing CRRT in 4 drug information references.

METHODS

Medications commonly prescribed during CRRT were identified from an institutional medication inventory database, and evidence-based dosage recommendations for this setting were developed from the primary and secondary literature. The American Hospital Formulary System-Drug Information (AHFS-DI), Micromedex 2.0 (specifically the DRUGDEX and Martindale databases), and the 5th edition of Drug Prescribing in Renal Failure (DPRF5) were assessed for the presence of drug dosage recommendations in the CRRT setting. The dosage recommendations in these tertiary references were compared with the recommendations derived from the primary and secondary literature to determine concordance.

RESULTS

Evidence-based drug dosage recommendations were developed for 33 medications administered in patients undergoing CRRT. The AHFS-DI provided no dosage recommendations specific to CRRT, whereas the DPRF5 provided recommendations for 27 (82%) of the medications and the Micromedex 2.0 application for 20 (61%) (13 [39%] in the DRUGDEX database and 16 [48%] in the Martindale database, with 9 medications covered by both). The dosage recommendations were in concordance with evidence-based recommendations for 12 (92%) of the 13 medications in the DRUGDEX database, 26 (96%) of the 27 in the DPRF5, and all 16 (100%) of those in the Martindale database.

CONCLUSIONS

One prominent tertiary drug information resource provided no drug dosage recommendations for patients undergoing CRRT. However, 2 of the databases in an Internet-based medical information application and the latest edition of a renal specialty drug information resource provided recommendations for a majority of the medications investigated. Most dosage recommendations were similar to those derived from the primary and secondary literature. The most recent edition of the DPRF is the preferred source of information when prescribing dosage regimens for patients receiving CRRT.

[Drugs dosing in intensive care unit during continuous renal replacement therapy]

Drug dosing in the intensive care unit can be challenging. Acute kidney injury (AKI) is a common complication of sepsis and a part of multiple organ dysfunction syndrome. Continuous renal replacement therapy (CRRT) is increasingly used as dialysis therapy in this critically ill population. Available data demonstrate that sepsis, AKI and different modalities of CRRT can profoundly change drugs pharmacokinetic. The severity of these changes depends on molecules characteristics (volume of distribution, plasma protein binding, molecular weight, plasma half-life, plasma clearance), patient itself (volemia, residual renal function, tissue perfusion, hepatic dysfunction) and modality of CRRT (diffusion, convection, adsorption). There are no available recommendations to adapt drug dosing in a given critically ill patient with a given modality of CRRT. It is necessary to fully understand the different methods of CRRT and drug pharmacokinetic to prescribe the appropriate dose and to avoid under or potentially toxic overdosing. Monitoring the plasma level of drug - when available - can establish a relation between the blood concentration and its effect; thus, facilitating drug dosing.

Improved clinical outcome of paediatric bone marrow recipients using a test dose and Bayesian pharmacokinetic individualization of busulfan dosage regimens

In order to control busulfan pharmacokinetic variability and toxicity, a specific monitoring protocol was instituted in our bone marrow transplant BMT paediatric patients including a test dose, daily Bayesian forecasting of busulfan plasma levels, and Bayesian individualization of busulfan dosage regimens. Twenty-nine children received BMT after a busulfan-based conditioning regimen. Individual pharmacokinetic parameters were obtained following a 0.5 mg*kg test dose and were used for daily individualization of dosage regimens during the subsequent 4-day course of treatment. Doses were adjusted to reach a target mean AUC per 6 h between 4 and 6 microg.h.ml(+1). Plasma busulfan assays were performed by liquid chromatography. Pharmacokinetic analysis used the USC*PACK software. The performance of the test dose to predict AUC during the busulfan regimen was evaluated. Incidence of toxicity, chimerism and relapse, overall Kaplan-Meier survival, and VOD-free survival were compared after matching our patients (group A) with patients conditioned by using standard doses of busulfan (group B). Busulfan doses were decreased in 69% of patients compared to conventional doses. Expected AUC was significantly correlated with observed AUC and predictability of the test dose was 101.9 +/- 17.9%. Incidence of VOD in group A was 3.4% vs 24.1% in group B, while the incidence of stomatitis was similar. Engraftment was successful in all patients in group A. The rate of full engraftment at 3 months post-BMT was higher in group A (P = 0.012). Long-term overall survival did not differ between the two groups, in contrast to the 90-day survival. VOD-free survival was higher in group A (P = 0.026). Pharmacokinetic monitoring and individualization of busulfan dosage regimen are useful in improving clinical outcome and reducing early mortality in paediatric bone marrow transplant recipients.