Metformin in chronic kidney disease: more harm than help?

Anticonstriction Effect of MCA in Rats by Danggui Buxue Decoction

Objective: Danggui Buxue decoction (DBD), consisting of Angelicae Sinensis Radix (ASR) and Astragali Radix (AR), is a famous prescription with the function of antivasoconstriction. This study intends to probe its mechanisms on the relaxation of the middle cerebral artery (MCA).

Methods: Vascular tension of rat MCA was measured using a DMT620 M system. First, the identical series of concentrations of DBD, ASR, and AR were added into resting KCl and U46619 preconstricted MCA. According to the compatibility ratio, their dilatation effects were further investigated on KCl and U46619 preconstricted vessels. Third, four K⁺ channel blockers were employed to probe the vasodilator mechanism on KCl-contracted MCA. We finally examined the effects of DBD, ASR, and AR on the vascular tone of U46619-contracted MCA in the presence or absence of Ca²⁺.

Results: Data suggested that DBD, ASR, and AR can relax on KCl and U46619 precontracted MCA with no effects on resting vessels. The vasodilator effect of ASR was greater than those of DBD and AR on KCl-contracted MCA. For U46619-contracted MCA, ASR showed a stronger vasodilator effect than DBD and AR at low concentrations, but DBD was stronger than ASR at high concentrations. Amazingly, the vasodilator effect of DBD was stronger than that of AR at all concentrations on two vasoconstrictors which evoked MCA. The vasodilator effect of ASR was superior to that of DBD at a compatibility ratio on KCl-contracted MCA at low concentrations, while being inferior to DBD at high concentrations. However, DBD exceeded AR in vasodilating MCA at all concentrations. For U46619-constricted MCA, DBD, ASR, and AR had almost identical vasodilation. The dilation of DBD and AR on KCl-contracted MCA was independent of K⁺ channel blockers. However, ASR may inhibit the K⁺ channel opening partially through synergistic interactions with Gli and BaCl₂. DBD, ASR, and AR may be responsible for inhibiting [Ca²⁺]_out, while ASR and AR can also inhibit [Ca²⁺]_in.

Conclusion: DBD can relax MCA with no effects on resting vessels. The mechanism may be related to ASR’s inhibition of K_ATP and K_ir channels. Meanwhile, the inhibition of [Ca²⁺]_out by DBD, ASR, and AR as well as the inhibition of [Ca²⁺]_in by ASR and AR may contribute to dilate MCA.

Novel management of diabetes in kidney transplantation

PURPOSE OF REVIEW

Posttransplant diabetes mellitus (PTDM) is a prevalent complication in kidney transplant recipients, and has been associated with worse short-term and long-term outcomes.

RECENT FINDINGS

While hyperglycemia is frequently seen in the early posttransplant period because of surgical stress, infection, and use of high-dose steroids, the diagnosis of PTDM should be established after patients are clinically stable and on stable maintenance immunosuppression. In the early posttransplant period, hyperglycemia is typically treated with insulin, and pilot data have suggested potential benefit of lower vs. higher glycemic targets in this setting. Growing data indicate lifestyle modifications, including dietary interventions, physical activity, and mitigation of obesity, are associated with improved posttransplant outcomes. While there are limited data to support a first-line antidiabetic medication for PTDM, more established pharmacotherapies such as sulfonylureas, meglitinides, and dipetidyl peptidase IV inhibitors are commonly used. Given recent trials showing the benefits of sodium-glucose cotransporter 2 inhibitors and glucagon-like peptide 1 receptor agonists upon kidney outcomes in nontransplant patients, further study of these agents specifically in kidney transplant recipients are urgently needed.

SUMMARY

Increasing evidence supports a multidisciplinary approach, including lifestyle modification, obesity treatment, judicious immunosuppression selection, and careful utilization of novel antidiabetic therapies in PTDM patients.

Hypoglycemia-Related Hospitalizations and Mortality Among Patients With Diabetes Transitioning to Dialysis

RATIONALE & OBJECTIVE

Diabetic patients with declining kidney function are at heightened risk for hypoglycemia. We sought to determine whether hypoglycemia-related hospitalizations in the interval before dialysis therapy initiation are associated with post-end-stage renal disease (ESRD) mortality among incident patients with ESRD with diabetes.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

US veterans from the national Veterans Affairs database with diabetes and chronic kidney disease transitioning to dialysis therapy from October 2007 to September 2011.

EXPOSURE

Hypoglycemia-related hospitalizations during the pre-ESRD period and antidiabetic medication regimens.

OUTCOME

The outcome of post-ESRD all-cause mortality was evaluated relative to pre-ESRD hypoglycemia. The outcome of pre-ESRD hypoglycemia-related hospitalization was evaluated relative to antidiabetic medication regimens.

ANALYTIC APPROACH

We examined whether the occurrence and frequency of pre-ESRD hypoglycemia-related hospitalizations are associated with post-ESRD mortality using Cox regression models adjusted for case-mix covariates. In a subcohort of patients prescribed 0 to 2 oral antidiabetic drugs and/or insulin, we examined the 12 most commonly prescribed antidiabetic medication regimens and risk for pre-ESRD hypoglycemia-related hospitalization using logistic regression models adjusted for case-mix covariates.

RESULTS

Among 30,156 patients who met eligibility criteria, the occurrence of pre-ESRD hypoglycemia-related hospitalization(s) was associated with higher post-ESRD mortality risk: adjusted HR (aHR), 1.25; 95% CI, 1.17-1.34 (reference group: no hypoglycemia hospitalization). Increasing frequency of hypoglycemia-related hospitalizations was independently associated with incrementally higher mortality risk: aHRs of 1.21 (95% CI, 1.12-1.30), 1.47 (95% CI, 1.19-1.82), and 2.07 (95% CI, 1.46-2.95) for 1, 2, and 3 or more hypoglycemia-related hospitalizations, respectively (reference group: no hypoglycemia hospitalization). Compared with patients who were prescribed neither oral antidiabetic drugs nor insulin, medication regimens that included sulfonylureas and/or insulin were associated with higher risk for hypoglycemia.

LIMITATIONS

Residual confounding cannot be excluded.

CONCLUSIONS

Among incident patients with ESRD with diabetes, a dose-dependent relationship between frequency of pre-ESRD hypoglycemia-related hospitalizations and post-ESRD mortality was observed. Further study of diabetic management strategies that prevent hypoglycemia as patients with chronic kidney disease transition to ESRD are warranted.

Fatal Case of Metformin-Associated Lactic Acidosis Associated With Temporary Ileostomy: A Case Report

BACKGROUND

Metformin is considered a first choice for oral treatment of patients with type 2 diabetes in the absence of contraindications. Colorectal cancer is the second most frequent cancer among the general population; low anterior resections and temporary diverting ileostomies are commonly performed in this population. As the incidence of type 2 diabetes increases, the use of metformin in patients with both type 2 diabetes and an ileostomy will most likely increase as well.

CASE

We present the case of a patient affected by colorectal cancer who developed a severe metformin-associated lactic acidosis (MALA) after creation of a temporary ileostomy to protect a low colorectal anastomosis. High-volume output from his ileostomy led to significant fluid loss and electrolyte imbalance, his condition was complicated by MALA, resulting in death.

CONCLUSION

The population of ileostomy patients who also have type 2 diabetic and taking metformin is at risk for MALA. High stomal output can lead to dehydration, with a loss of fluids and electrolytes and metformin could aggravate this condition, potentiating the risk of MALA.

Risks of Metformin in Type 2 Diabetes and Chronic Kidney Disease: Lessons Learned from Taiwanese Data

Like other biguanide agents, metformin is an anti-hyperglycemic agent with lower tendency towards hypoglycemia compared to other anti-diabetic drugs. Given its favorable effects on serum lipids, obese body habitus, cardiovascular disease, and mortality, metformin is recommended as the first-line pharmacologic agent for type 2 diabetes in the absence of contraindications. However, as metformin accumulation may lead to type B non-hypoxemic lactic acidosis, especially in the setting of kidney injury, chronic kidney disease, and overdose, regulatory agencies such as the United States Food and Drug Administration (FDA) have maintained certain restrictions regarding its use in kidney dysfunction. Case series have demonstrated a high fatality rate with metformin-associated lactic acidosis (MALA), and the real-life incidence of MALA may be underestimated by observational studies and clinical trials that have excluded patients with moderate-to-advanced kidney dysfunction. A recent study of advanced diabetic kidney disease patients in Taiwan in Lancet Endocrinology and Diabetes has provided unique insight into the potential consequences of unrestricted metformin use, including a 35% higher adjusted mortality risk that was dose-dependent. This timely study, as well as historical data documenting the toxicities of other biguanides, phenformin and buformin, suggest that the recent relaxation of FDA recommendations to expand metformin use in patients with kidney dysfunction (i.e., those with estimated glomerular filtration rates ≥30 instead of our recommended ≥45 ml/min/1.73 m2) may be too liberal. In this article, we will review the history of metformin use; its pharmacology, mechanism of action, and potential toxicities; and policy-level changes in its use over time.

Should Restrictions Be Relaxed for Metformin Use in Chronic Kidney Disease? No, We Should Never Again Compromise Safety!

Metformin is and has been considered as first-line therapy for type 2 diabetes for over a quarter of a century. Like other biguanides, metformin can cause a lactic acidosis that is exceptionally rare but fatal. The likelihood of metformin-associated lactic acidosis is substantially higher in patients with kidney impairment and also among those with seemingly normal kidney function who are at risk of acute kidney injury (AKI). Hence, regulatory agencies in many industrialized nations have maintained strict renal restrictions surrounding metformin. However, there have been millions of people exposed to metformin for many years, many of them with serum creatinine values at or close to 1.5 mg/dL with estimated glomerular filtration rates (eGFRs) much below 60 mL/min/1.73 m(2) who have not developed lactic acidosis. Thus, there clearly remains controversy in this area, and there has been heightened pressure to remove the renal restrictions of metformin. To provide a discussion on the pros and cons of relaxing the renal restrictions for metformin use, we provide a Point-Counterpoint. In the point narrative below, Drs. Kalantar-Zadeh and Kovesdy provide their argument that although there is little evidence of the potential benefits of metformin in kidney disease, just considering the sheer numbers of metformin users and the high fatality rate of its associated lactic acidosis, the most appropriate practice is to avoid metformin use in people with eGFR <45 mL/min/1.73 m(2) or in those who are at high risk of AKI irrespective of underlying eGFR. In the following counterpoint narrative, Drs. Bakris and Molitch argue that the data from a very large analysis demonstrate clearly that serum creatinine should be supplanted with eGFR as the criteria for metformin use and that the incidence of lactic acidosis is only elevated in those with a reduced eGFR who become dehydrated for various reasons or in those exposed to some toxin resulting in AKI. Otherwise the data clearly support the use of metformin under normal circumstances down to eGFR >30 mL/min/1.73 m(2)-William T. CefaluEditor in Chief, Diabetes Care.

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.