Dosing adjustment of 10 antimicrobials for patients with renal impairment

Evaluation of applying drug dose adjustment by physicians in patients with renal impairment

OBJECTIVE

To determine whether appropriate dose adjustment was taken into account or not by the physicians when prescribing drugs in patients with renal impairment.

DESIGN

A retrospective chart review was performed and included 98 adult in-patients, diagnosed with renal impairment based on clinical evaluation and laboratory data, in King Abdulaziz University Hospital (KAUH), Jeddah, Saudi Arabia, who was admitted to the hospital from September 2005 to January 2011. Data of the patients were noted and recorded including baseline demographics, clinical data, laboratory data, renal state, treatment data and medications.

RESULTS

The initial number of the patients was reduced to 80 where a total of 502 drugs were investigated in the present study with an average of six drugs per patient. Of these 502 studied drugs, 196 (39%) required dose adjustment where 92 (46.9%) were adjusted and 104 (53.1%) were not adjusted. It was found also that most of the drugs requiring dose adjustment were antibiotics (39.8%).

CONCLUSION

The current study confirms that physicians still do not take into account sufficiently patients' renal function when prescribing drugs. Continuous medical education and collaboration with clinical pharmacist should be encouraged for quality improvement in patients with renal impairment.

Drug Use and Dosing in Chronic Kidney Disease

One of the most important drug-related problems in patients with chronic kidney disease (CKD) is medication dosing errors. Many medications and their metabolites are eliminated through the kidney. Thus, adequate renal function is important to avoid toxicity. Patients with renal impairment often have alterations in their pharmacokinetic and pharmacodynamic pa-rameters. The clearance of drugs eliminated primarily by renal filtration is decreased by renal disease. Therefore, special consideration should be taken when these drugs are prescribed to patients with impaired renal function. Despite the importance of dosage adjustment in patients with CKD, such adjustments are sometimes ignored. Physicians and pharmacists can work together to accomplish safe drug prescribing. This task can be complex and require a stepwise approach to ensure effectiveness, minimise further damage and prevent drug nephrotoxicity. Key words: Dosage adjustment, Renal impairment, Stepwise approach

Impact of a Renal Drug Dosing Service on Dose Adjustment in Hospitalized Patients with Chronic Kidney Disease

Background:

Appropriate drug selection and dosing for patients with chronic kidney disease (CKD) is important to avoid unwanted drug effects and ensure optimal patient outcomes.

Objective:

To assess the rate of inappropriate dosing in patients with CKD in a nephrology unit and to evaluate the impact on dose adjustment, adverse drug events (ADEs), and drug cost of having a pharmacist accompany a team of physicians on their rounds.

Methods:

This was a comparative study with a preintervention and postintervention design. The preintervention phase served as the control; it was prospective and observational only and was conducted from the beginning of February to the end of May 2007. The second phase (intervention phase) was conducted from the beginning of March to the end of June 2008. Two random samples of 300 patients with an estimated creatinine clearance less than or equal to 50 mL/min were included. During the intervention phase, a clinical pharmacist made rounds with the nephrology unit team and gave dosing adjustment recommendations when needed. A collection of reliable and up-to-date drug information references that are commonly used globally were used during the intervention.

Results:

In the preintervention group, drug dosage adjustment or avoidance, based on renal function, was necessary in 607 of 2814 (21.6%) prescriptions. Of these, 322 (53.0%) did not comply with guidelines. In the intervention group, adjustment was necessary for 640 of 2981 (21.5%) prescriptions. The pharmacist made 388 recommendations related to dosing adjustment, 212 (54.6%) of which were accepted by physicians. Clinicians' noncompliance with dosing guidelines decreased to 176 (27.5%) (p < 0.001). In the preintervention group, 64 (21.3%) patients had a suspected ADE, with a total of 73 events. In the intervention group, this number was significantly lower with 49 events in 48 (16.0%) patients (p < 0.05). The intervention resulted in drug cost savings of $2250 US.

Conclusions:

A renal drug dosing service for patients hospitalized with CKD can increase the proportion of drug dosing that is adjusted to take into account renal function. This can save drug costs and may prevent ADEs.

Comparison of methods of assessment of renal function in cystic fibrosis (CF) patients

Renal failure is increasingly being recognised in CF patients, usually as a consequence of long-term nephrotoxic therapy. There is a need for a simple method of assessment of renal function in this patient group. We compared measured creatinine clearance from validated timed urine collections (the generally accepted practical test of glomerular filtration) with 10 formulae used to estimate creatinine clearance in a group of 74 CF adult patients and 29 matched normal controls. Compared to direct measurement, formulae gave a range of values (95% CI for mean bias -13 to +27.9 ml/min). Even those with the best correlation (r=0.7) gave wide error ranges (limits of agreement: -42.3 to 45.9 ml/min). The most commonly used formulae (Cockroft-Gault [CGF] and abbreviated Modification of Diet in Renal Disease [aMDRD]) were not superior to most other formulae tested. Both CGF and aMDRD-derived estimates compared less favourably in CF patients than controls (mean bias: 9.7 vs 3.4 ml/min (p<0.05) and 4.9 vs 1.4 (p<0.05) respectively; 78% vs 95% (p<0.01) and 77% vs 97% (p<0.01) of estimates within 33% of measurement respectively). In particular, both CGF and aMDRD grossly overestimated renal function (mean bias 18.3 and 15.8 ml/min respectively, p<0.001) in CF patients with reduced creatinine clearance (<80 ml/min). CGF, aMDRD and other formulae cannot be used to reliably assess renal function in CF patients, since they will fail to detect those with renal impairment. Some form of carefully supervised direct measurement is still required.

Pharmacodynamics of antiinfective therapy: taking what we know to the patient's bedside

Applied pharmacokinetics has long been a lifeline of clinical pharmacy services. National surveys during the past decade documented clinical pharmacy services and demonstrated that a substantial rate of growth occurred in clinical pharmacokinetic consultations and management of drug therapy protocols. Pharmacodynamic principles of antiinfective agents are rapidly becoming a new paradigm of clinical pharmacy services. beta-Lactams, aminoglycosides, and fluoroquinolones represent the three classes of antiinfective agents that have made the most progress toward the clinical applications of pharmacodynamics. Pharmacodynamic parameters are being used to select and compare agents within an antiinfective class (e.g., fluoroquinolones), make modifications in the dosage (e.g., extended-interval dosing of aminoglycosides) and/or mode of administration (e.g., continuous infusion of beta-lactams), develop in vivo breakpoint determinations, and assess the development of bacterial resistance. In addition, pharmacodynamic parameters have influenced the clinical drug development of new (e.g., linezolid) and older (amoxicillin-clavulanate, fluoroquinolones) antiinfective agents. Further investigations are needed to explore the clinician's use of validated prediction methods and patient-specific pharmacodynamic parameters at the bedside. By linking pharmacokinetic services with pharmacodynamic principles, the opportunity for continued progress toward our assessment and decisions for successful clinical outcomes is possible with old and new antiinfective agents.

Drug dosage in patients with renal failure optimized by immediate concurrent feedback

OBJECTIVE

To examine the impact of immediate concurrent feedback on dose adjustment in patients with renal failure.

DESIGN

Prospective 12-month study in patients with various degrees of renal failure, with comparison to a retrospective control group.

SETTING

A 39-bed unit of a university hospital providing primary and tertiary care.

PATIENTS

Patients with renal failure (estimated creatinine clearance < or = 50 mL/min) receiving at least 1 pharmacologically active drug.

INTERVENTIONS

Education of physicians and immediate concurrent feedback on the ward giving estimated creatinine clearance and dose recommendations for renally eliminated drugs adjusted to individual renal function.

MEASUREMENTS AND MAIN RESULTS

The percentage of dosage regimens adjusted to renal function and cost assessment of drug therapy were calculated. Overall, 17% of the patients had at least 1 estimated creatinine clearance < or = 50 mL/min. In the intervention group, the dose of 81% of renally eliminated drugs was adjusted to renal function, compared with 33% in the control group ( P <.001). The mean difference in cost between standard and adjusted dose of renally eliminated drugs in the intervention and control groups was 5.3 +/- 12.3 and 0.75 +/- 2.8 Swiss francs (approximately US$3.5 and US$0.5), respectively ( P <.001), accounting for 16.5% and 2.8%, respectively, of daily medication costs of all drugs.

CONCLUSIONS

The proportion of doses of renally eliminated drugs adjusted to renal function can be substantially increased by immediate concurrent feedback. This saves drug costs and has the potential to prevent adverse drug reactions.

Pharmacokinetics and pharmacodynamics of ceftizoxime in patients with dosages adjusted for renal function

STUDY OBJECTIVE

Our institution developed dosing guidelines for patients with renal impairment based on pharmacokinetic data and class-specific pharmacodynamics. Ceftizoxime was chosen as a model agent to evaluate if the modified guidelines achieved similar minimal plasma concentration (Cp(min)) and time above the minimum inhibitory concentration of the infecting organism (T>MIC) in patients with renal impairment versus those with normal renal function.

DESIGN

Prospective pharmacokinetic and pharmacodynamic evaluation of ceftizoxime dosages.

SETTING

University-affiliated hospital.

PATIENTS

Forty-three patients with suspected or documented infection were enrolled and classified into four groups based on creatinine clearance (Cl(cr); ml/min): group 1, above 100; group 2, 61-99; group 3, 31-60; and group 4, 15-30.

INTERVENTIONS

Ceftizoxime serum concentrations were obtained at steady state.

MEASUREMENTS AND MAIN RESULTS

Pharmacokinetic and pharmacodynamic parameters were calculated. As expected, clearance and elimination rate constant were reduced, and half-life tended to be greater in patients with renal impairment. The Cp(min) and area under the concentration-time curve over 24 hours were similar between groups (p=0.39, p=0.42). The T>MIC was 100% for all patient isolates, and 90% or more versus our clinical strain for all groups. Clinical outcomes were similar among all groups.

CONCLUSION

Our dosing guidelines achieved similar Cp(min) among all groups of patients. Our results support that recommendations for dosing adjustments should be based on pharmacokinetic data and must also consider pharmacodynamic parameters.