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Duong JK, Kroonen MYAM, Kumar SS, Heerspink HL, Kirkpatrick CM, Graham GG, Williams KM, Day RO. A dosing algorithm for metformin based on the relationships between exposure and renal clearance of metformin in patients with varying degrees of kidney function. Eur J Clin Pharmacol 2017; 73:981-990. [PMID: 28451709 DOI: 10.1007/s00228-017-2251-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 03/30/2017] [Indexed: 02/02/2023]
Abstract
PURPOSE The aims of this study were to investigate the relationship between metformin exposure, renal clearance (CLR), and apparent non-renal clearance of metformin (CLNR/F) in patients with varying degrees of kidney function and to develop dosing recommendations. METHODS Plasma and urine samples were collected from three studies consisting of patients with varying degrees of kidney function (creatinine clearance, CLCR; range, 14-112 mL/min). A population pharmacokinetic model was built (NONMEM) in which the oral availability (F) was fixed to 0.55 with an estimated inter-individual variability (IIV). Simulations were performed to estimate AUC0-τ, CLR, and CLNR/F. RESULTS The data (66 patients, 327 observations) were best described by a two-compartment model, and CLCR was a covariate for CLR. Mean CLR was 17 L/h (CV 22%) and mean CLNR/F was 1.6 L/h (69%).The median recovery of metformin in urine was 49% (range 19-75%) over a dosage interval. When CLR increased due to improved renal function, AUC0-τ decreased proportionally, while CLNR/F did not change with kidney function. Target doses (mg/day) of metformin can be reached using CLCR/3 × 100 to obtain median AUC0-12 of 18-26 mg/L/h for metformin IR and AUC0-24 of 38-51 mg/L/h for metformin XR, with Cmax < 5 mg/L. CONCLUSIONS The proposed dosing algorithm can be used to dose metformin in patients with various degrees of kidney function to maintain consistent drug exposure. However, there is still marked IIV and therapeutic drug monitoring of metformin plasma concentrations is recommended.
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Affiliation(s)
- Janna K Duong
- School of Medical Sciences, Medicine, University of New South Wales, Sydney, Australia. .,Department of Clinical Pharmacology and Toxicology, St Vincent's Hospital, Sydney, Australia. .,Faculty of Pharmacy, The University of Sydney, Sydney, NSW, 2006, Australia.
| | - M Y A M Kroonen
- Department of Pharmacy and Pharmacology, University of Groningen, Groningen, The Netherlands
| | - S S Kumar
- School of Medical Sciences, Medicine, University of New South Wales, Sydney, Australia.,Department of Clinical Pharmacology and Toxicology, St Vincent's Hospital, Sydney, Australia
| | - H L Heerspink
- Department of Pharmacy and Pharmacology, University of Groningen, Groningen, The Netherlands
| | - C M Kirkpatrick
- Centre for Medicine Use and Safety, Monash University, Parkville, Australia
| | - G G Graham
- School of Medical Sciences, Medicine, University of New South Wales, Sydney, Australia.,Department of Clinical Pharmacology and Toxicology, St Vincent's Hospital, Sydney, Australia
| | - K M Williams
- School of Medical Sciences, Medicine, University of New South Wales, Sydney, Australia.,Department of Clinical Pharmacology and Toxicology, St Vincent's Hospital, Sydney, Australia
| | - R O Day
- School of Medical Sciences, Medicine, University of New South Wales, Sydney, Australia.,Department of Clinical Pharmacology and Toxicology, St Vincent's Hospital, Sydney, Australia.,St Vincent's Clinical School, Medicine, University of New South Wales, Sydney, Australia
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Patel K, Batty KT, Moore BR, Gibbons PL, Kirkpatrick CM. Predicting the parasite killing effect of artemisinin combination therapy in a murine malaria model. J Antimicrob Chemother 2014; 69:2155-63. [DOI: 10.1093/jac/dku120] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Duong JK, Roberts DM, Furlong TJ, Kumar SS, Greenfield JR, Kirkpatrick CM, Graham GG, Williams KM, Day RO. Metformin therapy in patients with chronic kidney disease. Diabetes Obes Metab 2012; 14:963-5. [PMID: 22564555 DOI: 10.1111/j.1463-1326.2012.01617.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Revised: 04/12/2012] [Accepted: 05/02/2012] [Indexed: 12/11/2022]
Abstract
Metformin therapy is limited in patients with chronic kidney disease (CKD) due to the potential risk of lactic acidosis. This open-label observational study investigated metformin and lactate concentrations in patients with CKD (n = 22; creatinine clearances 15-40 ml/min) and in two dialysed patients. Patients were prescribed a range of metformin doses (250-2000 mg daily) and metformin concentrations were compared with data from healthy subjects (scaled to 1500 mg twice daily). A subset of patients (n = 7) was controlled on low doses of metformin (250 or 500 mg daily). No correlation between metformin and lactate concentrations was observed. Three patients had high lactate concentrations (>2.7 mmol/l) and two had high metformin concentrations (3-5 mg/l), but none had any symptoms of lactic acidosis. Reducing metformin dosage and monitoring metformin concentrations will allow the safe use of metformin in CKD, provided that renal function is stable.
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MESH Headings
- Acidosis, Lactic/blood
- Acidosis, Lactic/chemically induced
- Acidosis, Lactic/etiology
- Aged
- Aged, 80 and over
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/complications
- Diabetes Mellitus, Type 2/drug therapy
- Dose-Response Relationship, Drug
- Drug Administration Schedule
- Female
- Humans
- Hypoglycemic Agents/administration & dosage
- Hypoglycemic Agents/adverse effects
- Lactic Acid/blood
- Male
- Metformin/administration & dosage
- Metformin/adverse effects
- Middle Aged
- Renal Dialysis
- Renal Insufficiency, Chronic/blood
- Renal Insufficiency, Chronic/complications
- Renal Insufficiency, Chronic/therapy
- Risk Factors
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Stickland MD, Kirkpatrick CM, Begg EJ, Duffull SB, Oddie SJ, Darlow BA. An extended interval dosing method for gentamicin in neonates. J Antimicrob Chemother 2001; 48:887-93. [PMID: 11733474 DOI: 10.1093/jac/48.6.887] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Traditional gentamicin dosing every 8-24 h depending on age and weight in neonates does not provide the ideal concentration-time profile to both optimize the concentration-dependent killing by aminoglycosides and minimize toxicity. Fifty-three neonates were audited prospectively while receiving gentamicin 2.5 mg/kg every 8-24 h, aiming for peak concentrations (Cmax) of 6-10 mg/L and trough concentrations (Cmin) <2 mg/L. After the first dose, the mean (+/- s.d.) Cmax was 5.5 +/- 0.7 mg/L with sub-therapeutic concentrations (<6 mg/L) in 62% of patients, while the mean Cmin was >2 mg/L in 15% of the neonates. After the third dose the Cmax was 7.5 +/- 1.5 mg/L, with 17% <6 mg/L, whereas the mean Cmin was 2.2 +/- 1.1 mg/L with 49% of values >2 mg/L. An extended interval dosing method (24, 36 and 48 h) for infant weights of 0.75-5 kg was developed by simulation, and audited prospectively in 51 neonates. Prospective analysis of the extended interval dosing method showed a mean Cmax after the first dose of 13.1 +/- 3.6 mg/L, while the mean Cmin was 0.7 +/- 0.6 mg/L. Seventy-eight per cent had Cmax of >10 mg/L after the first dose. The mean area under the concentration versus time curve AUC0-24 was 93 mg*h/L (target = 100 mg*h/L). The extended interval dosing achieved higher Cmax values while ensuring that overall exposure per 24 h was acceptable. Prospective testing of the method demonstrated good predictive ability.
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Affiliation(s)
- M D Stickland
- Department of Paediatrics, Neonatal Intensive Care Unit, Christchurch Womens Hospital, Christchurch, New Zealand
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Kirkpatrick CM, Howard G, Vella-Brincat J. Comment: serum concentrations of cefuroxime after continuous infusion in coronary bypass graft patients. Ann Pharmacother 2001; 35:1295-6. [PMID: 11675869 DOI: 10.1345/aph.10183a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Abstract
AIMS To review the basis and optimal use of therapeutic drug monitoring of antimicrobial agents. METHODS Antimicrobial agents for which a reasonable case exists for therapeutic drug monitoring are reviewed under the following headings: pharmacokinetics, why monitor, therapeutic range, individualization of therapy, sampling times, methods of analysis, interpretative problems and cost-effectiveness of monitoring. RESULTS There is a strong historical case for monitoring aminoglycosides. The recent move to once-daily dosing means that criteria for therapeutic drug monitoring need to be redefined. Vancomycin has been monitored routinely but many questions remain about the most appropriate approach to this. A case can be made for monitoring teicoplanin, flucytosine and itraconazole in certain circumstances. CONCLUSIONS The approach to monitoring aminoglycosides is being redefined in the light of once daily dosing. It may be that less stringent monitoring is required in some circumstances but toxicity, especially ototoxicity, remains a problem with these drugs. Monitoring to avoid high AUCs (areas under the concentration-time curve) is recommended. The ideal method for monitoring vancomycin remains to be defined although a reasonable case exists for measuring trough concentrations, mainly to ensure efficacy. Teicoplanin is sometimes monitored to ensure efficacy while flucytosine may be monitored to avoid high concentrations associated with toxicity. Itraconazole has various pharmacokinetic problems and monitoring has been suggested to ensure that adequate concentrations are achieved.
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Affiliation(s)
- E J Begg
- Department of Clinical Pharmacology, Christchurch Hospital, Christchurch, New Zealand.
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Gardiner SJ, Begg EJ, Barclay ML, Kirkpatrick CM. Genetic polymorphism and outcomes with azathioprine and 6-mercaptopurine. Adverse Drug React Toxicol Rev 2000; 19:293-312. [PMID: 11212460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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Abstract
AIMS 1. To determine the population pharmacokinetics of gentamicin in 957 patients with varying renal function dosed once daily. 2. To see if current starting doses for once daily aminoglycoside dosing are appropriate. 3. To test whether calculating creatinine clearance using an adjusted Cockcroft and Gault method (CLCr,adjusted ) was a better predictor of gentamicin clearance than the standard Cockcroft and Gault method (CLCr,unadjusted ). METHODS Nine hundred and fifty-seven patients were dose-individualized for gentamicin using SeBA-GEN, a Bayesian dosing method. This method returns estimates of the values of gentamicin CL and V d from which the 24 h AUC can be estimated. The goal of therapy was to attain an AUC of 70-100 mg l-1 h depending on the severity of the infection. The population was divided into four groups of differing renal function. Linear regression analysis was performed to determine the relationship between V d and various indices of weight, and gentamicin CL and either CLCr,adjusted or CLCr,unadjusted. RESULTS The mean V d (+/-s. d.) and CL (+/-s.d.) of gentamicin in our total population were 17.4 (+/-4.1) l and 4.0 (+/-1.8) l h-1, respectively. There was a decrease in V d with reducing renal function when comparing patients with normal renal function and patients with poor renal function. The lower of total body weight (TBW) and lean body weight (LBW), termed dosing weight (DWT), was a slightly better predictor of V d (r2=0.28) than either TBW (r2=0.21) or LBW (r2=0.21). CLCr,adjusted (r2=0.80) was a better predictor of gentamicin CL than CLCr, unadjusted (r2=0.57). CONCLUSIONS The mean population values of V d and CL of gentamicin dosed once daily are similar to those described by others in relation to multiple daily dosing. Given that previous methods have been based on population values of V d and CL from multiple daily dosing, the currently recommended starting doses for once daily aminoglycoside dosing would seem appropriate. The V d reduced with decreasing renal function, with a maximum of 23% difference between patients with normal and poor renal function. The Cockcroft and Gault method of calculating creatinine clearance does not appear to perform well at low values of serum creatinine concentration. An adjustment of the Cockcroft and Gault method is proposed to allow for this.
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Affiliation(s)
- C M Kirkpatrick
- Department of Clinical Pharmacology, Christchurch Hospital, PO Box 4710, Christchurch, New Zealand
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Abstract
After 50 years of clinical experience with the aminoglycoside agents, there is continuing debate over the most appropriate administration regimen for these drugs. In recent years, once daily administration has been used increasingly, in the hope of both improving efficacy and reducing toxicity. At least 30 controlled clinical trials have compared once versus conventional multiple daily administration. Efficacy was assessed in some, but not all, studies using clinical and/or bacteriological cure. Toxicity was generally determined using rather nonsensitive end-points such as measurement of serum creatinine for nephrotoxicity and clinically detectable hearing loss for ototoxicity. The results of individual clinical trials and subsequent meta-analyses have been variable. However, 5 of 9 meta-analyses found clinical efficacy to be significantly better with once daily administration, and in 3 of the 9 there were significantly less nephrotoxicity with once daily administration. The results were not significant for ototoxicity in any of the meta-analyses. There is debate about how therapeutic drug monitoring should be performed, and whether it is still required with once daily administration. Previous experience with the aminoglycosides, especially in patients with impaired drug clearance caused by renal impairment, suggests that monitoring is still prudent. Results from the once daily administration trials appear to support this. Various methods of monitoring and dose adjustment have been proposed. The most common is to measure a 24-hour trough concentration and to adjust the dose to maintain the trough concentration below a value of 2, 1 or 0.5 mg/L. However, this method allows for greater total aminoglycoside exposure than has been permitted with conventional dosages, increasing the likelihood of toxicity in patients with impaired aminoglycoside clearance. Other methods measure drug concentrations at a time-point or points within the dose interval (when the concentration is still measurable), and adjust the dose according to concentration-time curve nomograms or to a target area under the concentration-time curve. This allows the use of higher doses in those with high drug clearance. Furthermore, in patients with impaired clearance, drug exposure is limited to the same extent as, or less than, that with conventional multiple daily administration. To date no controlled trials have compared methods of dose-individualisation. In summary, in addition to a slight overall improvement in efficacy, once daily administration has resulted in a small reduction in nephrotoxicity. In the studies using more sensitive measures of toxicity, the differences in toxicity were greater, strengthening the case for once daily administration. Therapeutic drug monitoring is probably required with once daily administration. Methods which use mid-dosage interval concentrations to gauge drug exposure would seem to be preferable over trough concentration measurement.
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Affiliation(s)
- M L Barclay
- Department of Clinical Pharmacology, Christchurch Hospital, New Zealand
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Abstract
AIMS The excretion of phospholipids in urine may be a marker of the early renal toxicity of the aminoglycoside antibiotics. Urinary phospholipids are formed in myeloid bodies which develop in the lysosomes of proximal tubules during treatment with the aminoglycosides, and overflow into the urine. METHODS Published assays were modified in order to measure the total phospholipid concentrations in human urine. Phospholipids were extracted from freeze-dried urine samples, digested in concentrated sulphuric acid, and the inorganic phosphorus content determined by complexing with ammonium molybdate and measuring the absorbance at 820 nm. Ten septicaemic patients treated with gentamicin for 5-7 days had significantly higher urine phospholipid concentrations than 10 healthy untreated control subjects (P < 0.0001). There was a negative linear relationship between phospholipid excretion and creatinine clearance (r2 = 0.71). RESULTS In 34 patients with acute pyelonephritis, increased phospholipid concentrations were observed prior to treatment compared with healthy controls (P < 0.001) and did not alter during treatment with gentamicin. However, the phospholipid concentrations decreased significantly after treatment was completed (P < 0.03). CONCLUSIONS These studies suggest that urinary phospholipids may indicate early aminoglycoside toxicity but with poor specificity, as many of the infections being treated may themselves be associated with phospholipiduria.
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Abstract
AIMS Bayesian dose-individualization methods have been shown to have good predictive performance using minimal data points, and are now used widely in clinical practice. This study was designed to compare two computerised Bayesian dose-individualization methods, ABBOTTBASE and SeBA-GEN, in once-daily dosing of aminoglycosides. METHODS ABBOTTBASE uses the maximum a posteriori estimator (MAP) algorithm which analyses all available serum drug concentration data for individual patients simultaneously, while the prior model remains unchanged. SeBA-GEN analyses each data set sequentially while continually modifying the individual patient's prior model, allowing within-patient variability to be modelled. One hundred consecutive patients who received once-daily dosing of aminoglycosides were prospectively dose-individualized using either of these methods. Retrospectively the alternative dosing method was used to provide comparative data. The ability of the methods to predict subsequent serum aminoglycoside concentration data was assessed in terms of their predictive performance, bias and precision. RESULTS From the 100 patients, 277 serum aminoglycoside concentrations were available. Ninety-eight patients had serum concentrations available from the first dose and 55 from the second dose. Gentamicin was used in 96 patients. There was no significant bias when predicting peak concentrations from the prior model using either SeBA-GEN or ABBOTTBASE. The prior model used by ABBOTTBASE did, however, significantly underpredict the mid-dose concentration (mean bias = -0.79 mg l-1, 95% Confidence Interval [CI]: -1.3 to -0.3). When using the Bayesian algorithms for prediction of the second set of concentrations neither method was biased when predicting the peak concentration. ABBOTTBASE significantly overpredicted the mid-dose concentration (mean bias = 0.38 mg l-1, 95% CI: 0.03 to 0.74). The prior model used by SeBA-GEN was more precise at predicting both peak and mid-dose concentrations (P < 0.01), indicating better use of covariates. There was no difference between the methods in terms of estimation of the value of volume of distribution, but they differed significantly in the estimation of clearance (mean difference = 0.24 l h-1 for SeBA-GEN-ABBOTTBASE, 95% CI: 0.05 to 0.43). CONCLUSIONS Bayesian techniques appear to work well with once-daily aminoglycoside dosing. The method of incorporation of individual patient information into the prior model appears to be important in the optimum choice of the first dose. SeBA-GEN has an advantage in this and in the lack of bias related to predicting low concentrations compared with ABBOTTBASE.
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Affiliation(s)
- S B Duffull
- Department of Clinical Pharmacology, Christchurch Hospital, New Zealand
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Begg EJ, Duffull SB, Kirkpatrick CM. Single or multiple daily doses of aminoglycosides. Exposure to aminoglycosides should be monitored during treatment. BMJ 1996; 313:491. [PMID: 8776328 PMCID: PMC2351871 DOI: 10.1136/bmj.313.7055.491] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Abstract
Of 73 wild and domestic mammals tested from an area endemic for pseudorabies in swine, 16 showed natural pseudorabies virus infection, 8 from farms with no pseudorabies history. In transmission experiments with swine and raccoons (Procyon lotor), pseudorabies was not transmitted between raccoons but was transmitted reciprocally between raccoons and swine by contact and when either consumed infected carrion of the other. The fluorescent antibody tissue section test proved valuable in diagnosis of pseudorabies, especially when employed with the virus isolation test.
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Affiliation(s)
- C. M. Kirkpatrick
- Purdue University Agricultural Experiment Station Lafayette, Indiana
| | - A. C. Leopold
- Purdue University Agricultural Experiment Station Lafayette, Indiana
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