Metformin-associated lactic acidosis and factors associated with 30-day mortality

Background

Metformin-associated lactic acidosis (MALA) is a rare event but underrecognition may lead to unfavorable outcomes in type 2 diabetes patients. While many risk factors of MALA have been identified, how to reduce mortality from MALA is a matter of debate. This study aimed to explore the factors associated with 30-day mortality amongst MALA patients.

Methods

An observational study enrolled patients diagnosed with MALA between January 2014 and December 2017. MALA was defined by a history of metformin administration, metabolic acidosis (arterial blood gas pH <7.35 or HCO₃ <15 mmol/L), and elevated plasma lactate level (>5 mmol/L). We examined risk factors including age, sex, underlying diseases, current medications, blood tests, disease severity, and dialysis data. Mortality status was identified from medical records or report on telephone.

Results

We included 105 MALA patients. Most patients (95.2%) were diagnosed acute kidney injury stage 3 according to KDIGO 2012 definition. The 30-day mortality rate was 36.2% and dialysis rate was 85.7%. The survivors had higher proportions of underlying chronic kidney disease, presence of metabolic acidosis, receiving renal replacement therapy within 6 hours, and haemodialysis, whereas the non-survivors had higher percentage of hypertension and disease severity. Lower APACHE II score (HR = 0.95; 95%CI, 0.91–0.99; p = 0.038), time to dialysis < 6 hours (0.31; 0.14–0.69; 0.004), and haemodialysis (0.20;0.06–0.67; 0.010) were associated with lower 30-day mortality, using multivariate Cox-regression analysis.

Conclusions

Mortality rate amongst patients with MALA was high. Early dialysis treatment within 6 hours after admission and haemodialysis were independently associated with lower 30-day mortality. The large scale, well-designed studies need to confirm these encouraging results.

Metformin-associated lactic acidosis exacerbated by acute kidney injury in an overseas traveler

We report the case of metformin-associated lactic acidosis (MALA) exacerbated by acute kidney injury (AKI) in a 65-year-old Asian American woman who was an overseas traveler. She had vomiting and diarrhea before arriving in Osaka, Japan, from the Philippines. She suffered from worsening respiratory distress, consciousness loss and anuria the day after coming to Japan. When she arrived at our emergency room via ambulance, she appeared to be in a state shock. Arterial blood gas analysis revealed severe lactic acidosis (pH 6.681, PO₂ 302 Torr under O₂ supplementation, PCO₂ 15 Torr, HCO₃⁻1.7 mmol/L, and lactate 17.00 mmol/L). She also had renal failure (BUN 108 mg/dL and serum creatinine 8.68 mg/dL) with hyperkalemia (6.1 mEq/L). We collected medical information from family members, and found her prescription medicines including metformin, diuretics and angiotensin-converting enzyme inhibitor (ACEI). We diagnosed her with MALA due to an unintended overdose of metformin resulting from acute kidney injury that can be induced by ACEI and diuretics in the volume-depleted condition. We immediately started hemodialysis therapy. Although she had a temporary cardiopulmonary arrest at the beginning of the treatment, her physical status was gradually improved and the severe acidemia resolved. On hospital day 4, she had urine and no longer needed hemodialysis therapy. On day 14, she was discharged and returned to the United States without noticeable sequelae. This is a case report of an overseas traveler who was successfully rescued through the collection of accurate medical information and understanding of the pathological condition.

Lactate and Myocadiac Energy Metabolism

The myocardium is capable of utilizing different energy substrates, which is referred to as “metabolic flexibility.” This process assures ATP production from fatty acids, glucose, lactate, amino acids, and ketones, in the face of varying metabolic contexts. In the normal physiological state, the oxidation of fatty acids contributes to approximately 60% of energy required, and the oxidation of other substrates provides the rest. The accumulation of lactate in ischemic and hypoxic tissues has traditionally be considered as a by-product, and of little utility. However, recent evidence suggests that lactate may represent an important fuel for the myocardium during exercise or myocadiac stress. This new paradigm drives increasing interest in understanding its role in cardiac metabolism under both physiological and pathological conditions. In recent years, blood lactate has been regarded as a signal of stress in cardiac disease, linking to prognosis in patients with myocardial ischemia or heart failure. In this review, we discuss the importance of lactate as an energy source and its relevance to the progression and management of heart diseases.

The Association between Metformin Therapy and Lactic Acidosis

INTRODUCTION AND OBJECTIVES

There is increasing evidence to suggest that therapeutic doses of metformin are unlikely to cause lactic acidosis. The aims of this research were (1) to formally evaluate the association between metformin therapy and lactic acidosis in published case reports using two causality scoring systems, (2) to determine the frequency of pre-existing independent risk factors in published metformin-associated lactic acidosis cases, (3) to investigate the association between risk factors and mortality in metformin-associated lactic acidosis cases, and (4) to explore the relationship between prescribed metformin doses, elevated metformin plasma concentrations and the development of lactic acidosis in cases with chronic renal impairment.

METHODS

A systematic review was conducted to identify metformin-associated lactic acidosis cases. Causality was assessed using the World Health Organisation-Uppsala Monitoring Centre system and the Naranjo adverse drug reaction probability scale. Compliance to dosing guidelines was investigated for cases with chronic renal impairment as well as the association between steady-state plasma metformin concentrations prior to admission.

RESULTS

We identified 559 metformin-associated lactic acidosis cases. Almost all cases reviewed (97%) presented with independent risk factors for lactic acidosis. The prescribed metformin dose exceeded published guidelines in 60% of cases in patients with impaired kidney function. Metformin steady-state plasma concentrations prior to admission were predicted to be below the proposed upper limit of the therapeutic range of 5 mg/L.

CONCLUSIONS

Almost all cases of metformin-associated lactic acidosis reviewed presented with independent risk factors for lactic acidosis, supporting the suggestion that metformin plays a contributory role. The prescribed metformin dose, on average, exceeded the dosing recommendations by 1000 mg/day in patients with varying degrees of renal impairment but the predicted pre-admission plasma concentrations did not exceed the therapeutic range.

Demystifying Lactate in the Emergency Department

The role of lactic acid and its conjugate base, lactate, has evolved during the past decade in the care of patients in the emergency department (ED). A recent national sepsis quality measure has led to increased use of serum lactate in the ED, but many causes for hyperlactatemia exist outside of sepsis. We provide a review of the biology of lactate production and metabolism, the many causes of hyperlactatemia, and evidence on its use as a marker in prognosis and resuscitation. Additionally, we review the evolving role of lactate in sepsis care. We provide recommendations to aid lactate interpretation in the ED and highlight areas for future research.

Improved glycemic control with minimal systemic metformin exposure: Effects of Metformin Delayed-Release (Metformin DR) targeting the lower bowel over 16 weeks in a randomized trial in subjects with type 2 diabetes

Objective

Metformin use is restricted in patients with renal impairment due to potential excess systemic accumulation. This study evaluated the glycemic effects and safety of metformin delayed-release (Metformin DR), which targets metformin delivery to the ileum to leverage its gut-based mechanisms of action while minimizing systemic exposure.

Research designs and methods

Participants (T2DM [HbA1c 7–10.5%], eGFR ≥60 mL/min/1.73m², not taking metformin for ≥2 months) were randomized to QD placebo (PBO); QD Metformin DR 600, 900, 1200, or 1500 mg; or to single-blind BID Metformin immediate-release (IR) 1000 mg. The primary endpoint was change in HbA1c for Metformin DR vs. PBO at 16 weeks in the modified intent-to-treat (mITT) population (≥ 1 post-baseline HbA1c while on study drug), using a mixed-effects repeated measures model.

Results

571 subjects were randomized (56 years, 53% male, 80% white; BMI 32.2±5.5 kg/m²; HbA1c 8.6±0.9%; 51% metformin naive); 542 were in the mITT population. Metformin DR 1200 and 1500 mg significantly reduced HbA1c (-0.49±0.13% and -0.62±0.12%, respectively, vs. PBO -0.06±0.13%; p<0.05) and FPG (C_{average Weeks 4–16}: -22.3±4.2 mg/dL and -25.1±4.1 mg/dL, respectively vs. -2.5±4.2 mg/dL p<0.05). Metformin IR elicited greater HbA1c improvement (-1.10±0.13%; p<0.01 vs. Placebo and all doses of Metformin DR) but with ~3-fold greater plasma metformin exposure. Normalizing efficacy to systemic exposure, glycemic improvements with Metformin DR were 1.5-fold (HbA1c) and 2.1-fold (FPG) greater than Metformin IR. Adverse events were primarily gastrointestinal but these were less frequent with Metformin DR (<16% incidence) vs. Metformin IR (28%), particularly nausea (1–3% vs 10%).

Conclusion

Metformin DR exhibited greater efficacy per unit plasma exposure than Metformin IR. Future studies will evaluate the effects of Metformin DR in patients with type 2 diabetes and advanced renal disease.

Trial registration

Clinicaltrials.gov NCT02526524.

Effect of metformin on the survival of patients with ALL who express high levels of the ABCB1 drug resistance gene

BACKGROUND

In acute lymphoblastic leukemia (ALL), high ABCB1 gene expression has been associated with treatment resistance, which affects patient prognosis. Many preclinical reports and retrospective population studies have shown an anti-cancer effect of metformin. Therefore, the objective of this study was to assess the effect of metformin on the treatment regimen in patients with ALL who exhibited high levels of ABCB1 gene expression and to determine its impact on overall survival.

METHODS

A total of 102 patients with ALL were recruited; one group (n = 26) received metformin, and the other received chemotherapy (n = 76). Measurement of ABCB1 transcript expression was performed using qRT-PCR prior to treatment initiation. Survival analysis was performed using Kaplan-Meier curves. The impact of both the type of treatment and the level of expression on the response (remission or relapse) was analyzed by calculating the odds ratio.

RESULTS

The survival of patients with high ABCB1 expression was lower than those with low or absent ABCB1 gene expression (p = 0.030). In the individual analysis, we identified a benefit to adding metformin in the group of patients with high ABCB1 gene expression (p = 0.025). In the metformin user group, the drug acted as a protective factor against both therapeutic failure (odds ratio [OR] 0.07, 95% confidence interval [CI] 0.0037-1.53) and early relapse (OR 0.05, 95% CI 0.0028-1.153).

CONCLUSION

The combined use of metformin with chemotherapy is effective in patients with elevated levels of ABCB1 gene expression. Trial registration NCT 03118128: NCT.

Metformin-associated lactic acidosis (MALA): Moving towards a new paradigm

Although metformin has been used for over 60 years, the balance between the drug's beneficial and adverse effects is still subject to debate. Following an analysis of how cases of so-called "metformin-associated lactic acidosis" (MALA) are reported in the literature, the present article reviews the pitfalls to be avoided when assessing the purported association between metformin and lactic acidosis. By starting from pathophysiological considerations, we propose a new paradigm for lactic acidosis in metformin-treated patients. Metformin therapy does not necessarily induce metformin accumulation, just as metformin accumulation does not necessarily induce hyperlactatemia, and hyperlactatemia does not necessarily induce lactic acidosis. In contrast to the conventional view, MALA probably accounts for a smaller proportion of cases than either metformin-unrelated lactic acidosis or metformin-induced lactic acidosis. Lastly, this review highlights the need for substantial improvements in the reporting of cases of lactic acidosis in metformin-treated patients. Accordingly, we propose a check-list as a guide to clinical practice.

Metformin-Associated Lactic Acidosis Undergoing Renal Replacement Therapy in Intensive Care Units: A Five-Million Population-Based Study in the North-West of Italy

BACKGROUND

Metformin-associated lactic acidosis (MALA) is a severe complication of drug administration with significant morbidity and mortality. So far no study in large population areas have examined the incidence, clinical profile and outcome of acute kidney injury (AKI)-MALA patients admitted in intensive care units (ICUs) and treated by renal replacement therapy (MALA-RRT).

METHODS

Retrospective analysis over a 6-year period (2010-2015) in Piedmont and Aosta Valley regions (5,305,940 inhabitants, 141,174 diabetics treated with metformin) of all MALA-RRT cases.

RESULTS

One hundred and seventeen cases of AKI-MALA-RRT were observed (12.04/100,000 metformin treated diabetics, 1.45% of all RRT-ICU patients). Survival rate was 78.3%. The average duration of RRT was 4.0 days at mean dialysis effluent of 977 mL/kg/day. At admission most patients were dehydrated, and experienced shock and oliguria.

CONCLUSION

Our data showed that MALA-RRT is a common complication, needing more prevention. Adopted policy of early, extended, continuous and high efficiency dialysis could contribute to an observed high survival rate. Video Journal Club "Cappuccino with Claudio Ronco" at http://www.karger.com/?doi=471917.

Comparison of baseline characteristics and clinical course in Japanese patients with type 2 diabetes among whom different types of oral hypoglycemic agents were chosen by diabetes specialists as initial monotherapy (JDDM 42)

Little is known about the relationships between patient factors and the antihyperglycemic agents that have been prescribed as initial therapy by diabetes specialists for patients with type 2 diabetes. Moreover, there has been little clarification of the subsequent usage patterns and related factors that influenced the continuation or discontinuation of the drug or the addition of another drug. To provide information on these issues, we evaluated the clinical characteristics of Japanese patients with type 2 diabetes for whom different types of oral hypoglycemic agents (i.e., either sulfonylureas, biguanides, or DPP-4 inhibitors (DPP-4Is)) were chosen as initial monotherapy by diabetes specialists and evaluated subsequent usage patterns.Prescription data on 3 different antidiabetic agents from December 2009 to March 2015 from diabetes specialists' patient registries were used to identify variables at baseline related to initial prescriptions; also, the addition of another hypoglycemic drug or discontinuation of the initial therapy was evaluated 1 year after the initial prescription. Analyzed were data on 2666 patients who received initial monotherapy with either a sulfonylurea (305 patients), biguanide (951 patients), or DPP-4I (1410 patients). Patients administered sulfonylureas were older, had a lower body mass index (BMI), longer duration of diabetes, and worse glycemic control than recipients of biguanides. Use of biguanides was related to younger age, short duration of diabetes, and obesity but was negatively associated with poor glycemic control. Older age but neither obesity nor poor glycemic control was associated with DPP-4Is. In all 3 groups a high HbA1c value was related to adding another hypoglycemic agent to the initial therapy. Moreover, adding another drug to a DPP-4I was related to a younger age and higher BMI.Patients' age, duration of diabetes, obesity, and glycemic control at baseline influenced the choice of hypoglycemic agents. Selection of a biguanide differs greatly from that of a sulfonylurea or DPP-4I with regard to age and obesity.

Retrospective analysis of lactic acidosis-related parameters upon and after metformin discontinuation in patients with diabetes and chronic kidney disease

PURPOSE

To investigate association between renal functions, lactic acid levels and acid-base balance in type 2 diabetes patients with chronic kidney disease under metformin treatment and after metformin discontinuation in a real-life setting.

METHODS

A total of 65 patients with diabetes (mean age 68.5 ± 8.9 years, 56.9 % females) in whom metformin treatment was discontinued due to reduced glomerular filtration rate (GFR) were included in this retrospective study. Data on patient demographics, metformin treatment and laboratory findings on the last day of metformin treatment and 2-3 weeks after metformin discontinuation including blood lactate and creatinine, estimated glomerular filtration rate (eGFR) and acid-base balance measurements in blood [pH, bicarbonate, base excess] were collected from medical records. The correlation of lactate levels with eGFR, blood pH and creatinine levels and changes in laboratory findings after metformin discontinuation were evaluated.

RESULTS

Before metformin discontinuation, hyperlactatemia was observed in 78.5 % of patients and metabolic acidosis in 36.9 % of patients, but none had lactic acidosis. Patients with normolactatemia and hyperlactatemia were similar in terms of metformin dosage and laboratory parameters. Lactate levels were not significantly correlated with serum creatinine (r = -0.14; p = 0.263) and eGFR (r = 0.11, p = 0.374). After metformin discontinuation, a significant decrease was observed in median lactate levels (from 2.20 to 1.85 mmol/L; p = 0.002).

CONCLUSION

In conclusion, our findings support the low risk of MALA among patients with mild-to-moderate renal impairment and the likelihood of metformin to be an innocent bystander without a pathogenic role in the lactic acidosis in most cases.

Metformin-associated lactic acidosis: Current perspectives on causes and risk

Although metformin has become a drug of choice for the treatment of type 2 diabetes mellitus, some patients may not receive it owing to the risk of lactic acidosis. Metformin, along with other drugs in the biguanide class, increases plasma lactate levels in a plasma concentration-dependent manner by inhibiting mitochondrial respiration predominantly in the liver. Elevated plasma metformin concentrations (as occur in individuals with renal impairment) and a secondary event or condition that further disrupts lactate production or clearance (e.g., cirrhosis, sepsis, or hypoperfusion), are typically necessary to cause metformin-associated lactic acidosis (MALA). As these secondary events may be unpredictable and the mortality rate for MALA approaches 50%, metformin has been contraindicated in moderate and severe renal impairment since its FDA approval in patients with normal renal function or mild renal insufficiency to minimize the potential for toxic metformin levels and MALA. However, the reported incidence of lactic acidosis in clinical practice has proved to be very low (<10 cases per 100,000 patient-years). Several groups have suggested that current renal function cutoffs for metformin are too conservative, thus depriving a substantial number of type 2 diabetes patients from the potential benefit of metformin therapy. On the other hand, the success of metformin as the first-line diabetes therapy may be a direct consequence of conservative labeling, the absence of which could have led to excess patient risk and eventual withdrawal from the market, as happened with earlier biguanide therapies. An investigational delayed-release metformin currently under development could potentially provide a treatment option for patients with renal impairment pending the results of future studies. This literature-based review provides an update on the impact of renal function and other conditions on metformin plasma levels and the risk of MALA in patients with type 2 diabetes.

The Primary Glucose-Lowering Effect of Metformin Resides in the Gut, Not the Circulation: Results From Short-term Pharmacokinetic and 12-Week Dose-Ranging Studies

OBJECTIVE

Delayed-release metformin (Met DR) is formulated to deliver the drug to the lower bowel to leverage the gut-based mechanisms of metformin action with lower plasma exposure. Met DR was assessed in two studies. Study 1 compared the bioavailability of single daily doses of Met DR to currently available immediate-release metformin (Met IR) and extended-release metformin (Met XR) in otherwise healthy volunteers. Study 2 assessed glycemic control in subjects with type 2 diabetes (T2DM) over 12 weeks.

RESEARCH DESIGN AND METHODS

Study 1 was a phase 1, randomized, four-period crossover study in 20 subjects. Study 2 was a 12-week, phase 2, multicenter, placebo-controlled, dose-ranging study in 240 subjects with T2DM randomized to receive Met DR 600, 800, or 1,000 mg administered once daily; blinded placebo; or unblinded Met XR 1,000 or 2,000 mg (reference).

RESULTS

The bioavailability of 1,000 mg Met DR b.i.d. was ∼50% that of Met IR and Met XR (study 1). In study 2, 600, 800, and 1,000 mg Met DR q.d. produced statistically significant, clinically relevant, and sustained reductions in fasting plasma glucose (FPG) levels over 12 weeks compared with placebo, with an ∼40% increase in potency compared with Met XR. The placebo-subtracted changes from baseline in HbA1c level at 12 weeks were consistent with changes in FPG levels. All treatments were generally well tolerated, and adverse events were consistent with Glucophage/Glucophage XR prescribing information.

CONCLUSIONS

Dissociation of the glycemic effect from plasma exposure with gut-restricted Met DR provides strong evidence for a predominantly lower bowel-mediated mechanism of metformin action.

Metformin associated lactic acidosis (MALA): clinical profiling and management

Metformin (MF) accumulation during acute kidney injury is associated with high anion gap lactic acidosis type B (MF-associated lactic acidosis, MALA), a serious medical condition leading to high mortality. Despite dose adjustment for renal failure, diabetic patients with chronic kidney disease (CKD) stage III-IV are at risk for rapid decline in renal function by whatever reason, so that MF toxicity might arise if the drug is not timely withdrawn. Sixteen consecutive patients were admitted to our Hospital's Emergency Department with clinical findings consistent with MALA. Fifteen had prior history of CKD, 60 % of them with GFR between 30 and 60 ml/min. Of these, 5 required mechanical ventilation and cardiovascular support; 3 promptly recovered renal function after rehydration, whereas 10 (62 %) required continuous veno-venous renal replacement treatment. SOFA and SAPS II scores were significantly related to the degree of lactic acidosis. In addition, lactate levels were relevant to therapeutic choices, since they were higher in dialyzed patients than in those on conservative treatment (11.92 mmol/l vs 5.7 mmol/l, p = 0.03). The overall death rate has been 31 %, with poorer prognosis for worse acidemia, as serum pH was significantly lower in non-survivors (pH 6.96 vs 7.16, p > 0.04). Our own data and a review of the literature suggest that aged, hemodynamically frail patients, with several comorbidities and CKD, are at greater risk of MALA, despite MF dosage adjustment. Moreover, renal replacement therapy rather than simple acidosis correction by administration of alkali seems the treatment of choice, based on eventual renal recovery and overall outcome.

Comparison of clinical characteristics in patients with type 2 diabetes among whom different antihyperglycemic agents were prescribed as monotherapy or combination therapy by diabetes specialists

AIMS/INTRODUCTION

We compared clinical characteristics in patients with type 2 diabetes for whom different antihyperglycemic agents were prescribed as monotherapy or combination therapy by diabetes specialists in Japan.

MATERIALS AND METHODS

Prescription data for 2005, 2008 and 2011 from diabetes specialists' patient registries identified variables related to prescription of different antihyperglycemic agents.

RESULTS

A total of 33,251 prescriptions in 2005, 25,119 in 2008 and 20,631 in 2011 were analyzed. Prescribing insulin was related to younger age, long duration of diabetes and glycated hemoglobin (HbA1c) ≥8.0%, but was negatively associated with obesity. Prescribing sulfonylureas was related to older age and long duration of diabetes, but not to obesity. Use of biguanides was related to younger age, short duration of diabetes and obesity, but was negatively associated with HbA1c ≥8.0%. A short duration of diabetes and HbA1c ≥8.0% were associated with use of a DPP-4 inhibitor, but not with obesity. Prescribing GLP-1 receptor agonists was related to younger age, obesity and HbA1c ≥8.0%. Odds ratios for each antihyperglycemic combination therapy were determined based on the characteristics of each included antihyperglycemic agent.

CONCLUSIONS

These results could be expected to reflect in part the consensus of diabetes specialists, and might provide guidance regarding pharmacotherapy in the clinical setting.

Achieving glycemic control in elderly patients with type 2 diabetes: a critical comparison of current options

The prevalence of type 2 diabetes mellitus (T2DM) is increasing in the elderly. Because of the unique characteristics of elderly people with T2DM, therapeutic strategy and focus should be tailored to suit this population. This article reviews the guidelines and studies related to older people with T2DM worldwide. A few important themes are generalized: 1) the functional and cognitive status is critical for older people with T2DM considering their life expectancy compared to younger counterparts; 2) both severe hypoglycemia and persistent hyperglycemia are deleterious to older adults with T2DM, and both conditions should be avoided when determining therapeutic goals; 3) recently developed guidelines emphasize the avoidance of hypoglycemic episodes in older people, even in the absence of symptoms. In addition, we raise the concern of glycemic variability, and discuss the rationale for the selection of current options in managing this patient population.

Inappropriate metformin prescribing in elderly type 2 diabetes mellitus (T2DM) patients

PURPOSE

Metformin is the most commonly prescribed anti-diabetic medication. However, it is often used despite the presence of contraindications and in unlicensed indications. The main aim of this study was to evaluate the frequency of metformin use before hospitalization in spite of contraindications in patients with type 2 diabetes mellitus (T2DM) and to evaluate the prevalence of metformin - associated side effects.

MATERIAL/METHODS

558 hospitalized patients (mean age = 66.65 ± 12.73 years) with poorly controlled T2DM were enrolled. Detailed medical history including the duration of T2DM, duration of hypoglycemic agents usage prior to hospitalization and possible metformin-associated side effects was recorded. Patients were subjected to a thorough physical examination and indispensable biochemical and diagnostic research panel was performed to establish the degree of heart failure, sufficiency of the respiratory system and kidney function.

RESULTS

335 out of 558 patients were treated before hospitalization with metformin alone or in combination with other hypoglycemic agents, mostly sulfonylureas. Contraindications to metformin were found in 275 patients and despite this 120 of them were using this medication in an average dose of 1793.91 ± 701.61 mg. However, none of them reported any serious adverse effects and no significant pH changes were observed. Only three patients reported moderate dyspepsia.

CONCLUSIONS

The results of this study indicate a relatively good tolerability of metformin by patients with the traditional contraindications to this drug. These findings support other authors' suggestion that indications and contraindications to metformin should be re-evaluated.

Drug therapy in patients with chronic renal failure

BACKGROUND

Roughly 20% of patients in hospital have impaired kidney function. This is frequently overlooked because of the creatinine-blind range in which early stages of renal failure are often hidden. Chronic kidney disease is divided into 5 stages (CKD 1 to 5).

METHODS

Selective literature search.

RESULTS

Methotrexate, enoxaparin and metformin are examples of drugs that should no longer be prescribed if the glomerular filtration rate (GFR) is 60 mL/min or less. With antidiabetic (e.g. glibenclamide), cardiovascular (e.g. atenolol) or anticonvulsive (e.g. gabapentin) drugs, the advice is to use alternative preparations such as gliquidone, metoprolol or carbamazepine which are independent of kidney function. Drug dose adjustment should be considered with antimicrobial (e.g. ampicillin, cefazolin), antiviral (e.g. aciclovir, oseltamivir) and, most recently, also for half of all chemotherapeutic and cytotoxic drugs in patients with impaired kidney function (with e.g. cisplatin, for instance, but not with paclitaxel).

CONCLUSION

Decisions concerning drug dose adjustment must be based on the pharmacokinetics but this is an adequate prerequisite only in conjunction with the pharmacodynamics. There are two different dose adjustment rules: proportional dose reduction according to Luzius Dettli, and the half dosage rule according to Calvin Kunin. The latter leads to higher trough concentrations but is probably more efficient for anti-infective therapy.

Review on pharmacokinetics and pharmacodynamics and the aging kidney

In people who are aged >65 years, pharmacokinetics are influenced more by the loss of kidney function than by the aging process of any other organ. A GFR of 30 to 60 ml/min, suggestive of stage 3 kidney disease, is observed in 15 to 30% of elderly people. Drug dosing must be adjusted to both changing pharmacokinetics and pharmacodynamics; the pharmacodynamics might be influenced by the aging of other organs, too. Using our NEPharm database, we extracted abstracts with pharmacokinetic parameters since 1999 from a weekly PubMed search. The recorded data were analyzed and compared with published recommendations on drug dosage and use in the elderly. Purely age-related changes in pharmacokinetic parameters were recorded from publications on 127 drugs. The analysis of our NEPharm records revealed an average (mean +/- SD) age-related prolongation of half-life of 1.39-fold (corresponding to +39 +/- 61%). Contrasting to common opinion, mean changes in clearance (-1 +/- 54%) and volume of distribution (+24 +/- 56%) were even less. The modest changes in pharmacokinetics do not suggest general dosage modifications in the elderly for most drugs. Changes in pharmacodynamics justify the common medication rule in the elderly-"start low + go slow"-especially for drugs that act on the central nervous system; however, in the case of anti-infective and anticancer therapy, the rule should be "hit hard = start high + go fast" to produce the target effect also in the elderly.

Impact of acute kidney injury on metformin-associated lactic acidosis

OBJECTIVES

Metformin has been shown to reduce diabetic complications in overweight patients, and is increasingly used to treat this condition. However, this agent is associated with a rare but serious risk of lactic acidosis.

METHODS

From January 2004 to November 2008, 11 cases of metformin-associated lactic acidosis were seen at a medical center in Taiwan. The patients' records were retrospectively reviewed with respect to clinical presentation, biochemical data, therapeutic strategies, and outcomes.

RESULTS

Ten out of 11 patients with acute kidney injury were enrolled in this study. From their pre-existing states, these patients would have been considered at low risk of developing lactic acidosis. However, all of them had acute intercurrent conditions that might compromise renal function. Among them, six patients were ventilated and five patients had severe hypotension with vasoactive support. Nine patients received renal replacement therapy to clear the acidosis and treat the renal failure. All but one of our patients survived. Recovery of renal function was the general rule in survivors.

CONCLUSIONS

Metformin-associated lactic acidosis is commonly accompanied with acute kidney injury. In spite of the severity of their illness, the outcome is favorable with intensive support of the cardiovascular, respiratory, and renal systems.