[Combination therapy with insulin/sulfonylurea in the long-term therapy of type II diabetes following "secondary failure"]

Insulin Monotherapy Versus Insulin Combined with Other Glucose-Lowering Agents in Type 2 Diabetes: A Narrative Review

CONTEXT

Insulin can be prescribed as a monotherapy or a combined therapy with other anti-diabetic medications. In this narrative review, the authors aimed to gather data related to comparison of insulin monotherapy versus combination of insulin and other anti-diabetic treatments with regards to different outcome measures in type 2 diabetes.

EVIDENCE ACQUISITION

This study searched and focused on the most recently published systematic reviews and their references investigating issues related to the primary aim.

RESULTS

The current data available on this topic is heterogeneous and suffers from low quality with respect to most combination treatments. Considering the efficacy and safety of combination therapy of insulin with older hypoglycemic agents, in general metformin and pioglitazone have the best and worst profiles, respectively. Compared to insulin monotherapy, combination of insulin and metformin is associated with better glycemic control, reduced daily insulin dose, less hypoglycemia, and weight gain; combination of insulin and pioglitazone results in greater hypoglycemia and weight gain and is associated with increased risk of edema and heart failure. Regarding sulphonylurea, there is some concern regarding hypoglycemia and weight gain. Addition of dipeptidyl peptidase-4 inhibitors to insulin seems to be beneficial with respect to glycemic control without any significant adverse effects. New drugs, including glucagon-like peptide-1 agonists and sodium glucose co-transporter 2 inhibitors, have acceptable profiles with significant benefits regarding weight reduction when added on insulin therapy.

CONCLUSIONS

Considering the quality and longevity of evidence, compared to insulin monotherapy, insulin combined with metformin and pioglitazone has the best and worst profiles, respectively. New anti-diabetic medications have acceptable profiles yet are expensive. It is important for clinicians to meticulously weigh the advantages of combination therapy against the possible adverse effects with each drug class in every patient, individually.

Insulin monotherapy compared with the addition of oral glucose-lowering agents to insulin for people with type 2 diabetes already on insulin therapy and inadequate glycaemic control

BACKGROUND

It is unclear whether people with type 2 diabetes mellitus on insulin monotherapy who do not achieve adequate glycaemic control should continue insulin as monotherapy or can benefit from adding oral glucose-lowering agents to the insulin therapy.

OBJECTIVES

To assess the effects of insulin monotherapy compared with the addition of oral glucose-lowering agents to insulin monotherapy for people with type 2 diabetes already on insulin therapy and inadequate glycaemic control.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, ClinicalTrials.gov, the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) and reference lists of articles. The date of the last search was November 2015 for all databases.

SELECTION CRITERIA

Randomised controlled clinical trials of at least two months' duration comparing insulin monotherapy with combinations of insulin with one or more oral glucose-lowering agent in people with type 2 diabetes.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed risk of bias, extracted data and evaluated overall quality of the evidence using GRADE. We summarised data statistically if they were available, sufficiently similar and of sufficient quality. We performed statistical analyses according to the statistical guidelines in the Cochrane Handbook for Systematic Reviews of Interventions.

MAIN RESULTS

We included 37 trials with 40 treatment comparisons involving 3227 participants. The duration of the interventions ranged from 2 to 12 months for parallel trials and two to four months for cross-over trials.The majority of trials had an unclear risk of bias in several risk of bias domains. Fourteen trials showed a high risk of bias, mainly for performance and detection bias. Insulin monotherapy, including once-daily long-acting, once-daily intermediate-acting, twice-daily premixed insulin, and basal-bolus regimens (multiple injections), was compared to insulin in combination with sulphonylureas (17 comparisons: glibenclamide = 11, glipizide = 2, tolazamide = 2, gliclazide = 1, glimepiride = 1), metformin (11 comparisons), pioglitazone (four comparisons), alpha-glucosidase inhibitors (four comparisons: acarbose = 3, miglitol = 1), dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors) (three comparisons: vildagliptin = 1, sitagliptin = 1, saxagliptin = 1) and the combination of metformin and glimepiride (one comparison). No trials assessed all-cause mortality, diabetes-related morbidity or health-related quality of life. Only one trial assessed patients' treatment satisfaction and showed no substantial differences between the addition of either glimepiride or metformin and glimepiride to insulin compared with insulin monotherapy.Insulin-sulphonylurea combination therapy (CT) compared with insulin monotherapy (IM) showed a MD in glycosylated haemoglobin A1c (HbA1c) of -1% (95% confidence interval (CI) -1.6 to -0.5); P < 0.01; 316 participants; 9 trials; low-quality evidence. Insulin-metformin CT compared with IM showed a MD in HbA1c of -0.9% (95% CI -1.2 to -0.5); P < 0.01; 698 participants; 9 trials; low-quality evidence. We could not pool the results of adding pioglitazone to insulin. Insulin combined with alpha-glucosidase inhibitors compared with IM showed a MD in HbA1c of -0.4% (95% CI -0.5 to -0.2); P < 0.01; 448 participants; 3 trials; low-quality evidence). Insulin combined with DPP-4 inhibitors compared with IM showed a MD in HbA1c of -0.4% (95% CI -0.5 to -0.4); P < 0.01; 265 participants; 2 trials; low quality evidence. In most trials the participants with CT needed less insulin, whereas insulin requirements increased or remained stable in participants with IM.We did not perform a meta-analysis for hypoglycaemic events because the included studies used different definitions.. In most trials the insulin-sulphonylurea combination resulted in a higher number of mild episodes of hypoglycaemia, compared to the IM group (range: 2.2 to 6.1 episodes per participant in CT versus 2.0 to 2.6 episodes per participant in IM; low-quality evidence). Pioglitazone CT also resulted in more mild to moderate hypoglycaemic episodes compared with IM (range 15 to 90 episodes versus 9 to 75 episodes, respectively; low-quality evidence. The trials that reported hypoglycaemic episodes in the other combinations found comparable numbers of mild to moderate hypoglycaemic events (low-quality evidence).The addition of sulphonylureas resulted in an additional weight gain of 0.4 kg to 1.9 kg versus -0.8 kg to 2.1 kg in the IM group (220 participants; 7 trials; low-quality evidence). Pioglitazone CT caused more weight gain compared to IM: MD 3.8 kg (95% CI 3.0 to 4.6); P < 0.01; 288 participants; 2 trials; low-quality evidence. Metformin CT was associated with weight loss: MD -2.1 kg (95% CI -3.2 to -1.1), P < 0.01; 615 participants; 7 trials; low-quality evidence). DPP-4 inhibitors CT showed weight gain of -0.7 to 1.3 kg versus 0.6 to 1.1 kg in the IM group (362 participants; 2 trials; low-quality evidence). Alpha-glucosidase CT compared to IM showed a MD of -0.5 kg (95% CI -1.2 to 0.3); P = 0.26; 241 participants; 2 trials; low-quality evidence.Users of metformin CT (range 7% to 67% versus 5% to 16%), and alpha-glucosidase inhibitors CT (14% to 75% versus 4% to 35%) experienced more gastro-intestinal adverse effects compared to participants on IM. Two trials reported a higher frequency of oedema with the use of pioglitazone CT (range: 16% to 18% versus 4% to 7% IM).

AUTHORS' CONCLUSIONS

The addition of all oral glucose-lowering agents in people with type 2 diabetes and inadequate glycaemic control who are on insulin therapy has positive effects on glycaemic control and insulin requirements. The addition of sulphonylureas results in more hypoglycaemic events. Additional weight gain can only be avoided by adding metformin to insulin. Other well-known adverse effects of oral glucose-lowering agents have to be taken into account when prescribing oral glucose-lowering agents in addition to insulin therapy.

Insulin monotherapy versus combinations of insulin with oral hypoglycaemic agents in patients with type 2 diabetes mellitus

BACKGROUND

It is unclear whether patients with type 2 diabetes who have poor glycaemic control despite maximal oral hypoglycaemic agents (OHAs) should be commenced on insulin as monotherapy, or insulin combined with oral hypoglycaemic agents (insulin-OHA combination therapy).

OBJECTIVES

To assess the effects of insulin monotherapy versus insulin-OHA combinations therapy.

SEARCH STRATEGY

Eligible studies were identified by searching MEDLINE, EMBASE, and The Cochrane Library. Date of last search: May 2004.

SELECTION CRITERIA

Randomised controlled trials (RCTs) with 2 months minimum follow-up duration comparing insulin monotherapy (all schemes) with insulin-OHA combination therapy.

DATA COLLECTION AND ANALYSIS

Data extraction and assessment of study quality were undertaken by three reviewers in pairs.

MAIN RESULTS

Twenty RCTs (mean trial duration 10 months) including 1,811 participants, with mean age 59.8 years and mean known duration of diabetes 9.6 years. Overall, study methodological quality was low. Twenty-eight comparisons in 20 RCTs were ordered according to clinical considerations. No studies assessed diabetes-related morbidity, mortality or total mortality. From 13 studies (21 comparisons), sufficient data were extracted to calculate pooled effects on glycaemic control. Insulin-OHA combination therapy had statistically significant benefits on glycaemic control over insulin monotherapy only when the latter was applied as a once-daily injection of NPH insulin. Conversely, twice-daily insulin monotherapy (NPH or mixed insulin) provided superior glycaemic control to insulin-OHA combination therapy regimens where insulin was administered as a single morning injection. In more conventional comparisons, regimens utilising OHAs with bedtime NPH insulin provided comparable glycaemic control to insulin monotherapy (administered as twice daily, or multiple daily injections). Overall, insulin-OHA combination therapy was associated with a 43% relative reduction in total daily insulin requirement compared to insulin monotherapy. Of the 14 studies (22 comparisons) reporting hypoglycaemia, 13 demonstrated no significant difference in the frequency of symptomatic or biochemical hypoglycaemia between insulin and combination therapy regimens. No significant differences in quality of life related issues were detected. Combination therapy with bedtime NPH insulin resulted in statistically significantly less weight gain compared to insulin monotherapy, provided metformin was used +/-sulphonylurea. In all other comparisons no significant differences with respect to weight gain were detected.

REVIEWERS' CONCLUSIONS

Bedtime NPH insulin combined with oral hypoglycaemic agents provides comparable glycaemic control to insulin monotherapy and is associated with less weight gain if metformin is used.

Insulin versus a combination of insulin and sulfonylurea in the treatment of NIDDM patients with secondary oral failure

AIM

Comparison of the effectiveness of combined therapy vs. an insulin regimen in NIDDM patients with secondary failure of oral hypoglycemic agents. RESEARCH DESIGN, PATIENTS AND METHODS: 27 NIDDM patients were randomly allocated to Group A (n = 14, insulin) and Group B (n = 13, insulin and sulfonylurea) with crossover after 3 months. After the next 3 months a decision was made about the further treatment according to the metabolic control. The patients were then treated for another year with the more successful regimen. Metabolic control, residual beta-cell secretory capacity, degree of peripheral insulin resistance (clamp) and insulin dose were followed during the whole study.

RESULTS

(median, interquartile range, in brackets; *, statistically significant difference at P < 0.05): the combined therapy was better than insulin alone in 2/3 of patients. Glycemic control was better (HbA1c at 3 months: Group A = 7.9(1.1)% vs. Group B = 7.0(0.5)%*; HbA1c at 6 months: Group A = 7.4(1.5)% vs. Group B = 8.1(1.5)%. Insulin dose was lower during the combined therapy in the first 3 months: Group A = 0.62(0.18) U/kg body weight vs. Group B = 0.39(0.16) U/kg body weight*. Combined treatment was associated with increased C-peptide excretion both fasting and postprandially. No significant differences in peripheral insulin resistance were noted between the two groups. The combined treatment remained successful even after one year. The two groups of patients with different effective treatment did not differ significantly in any of the observed parameters.

CONCLUSIONS

the combined therapy was more effective than insulin alone. Its favourable effect persisted after treatment for a year. It seems better to start the treatment of the oral failure with combined therapy compared with insulin first and later followed by combined therapy. On the basis of the observed parameters it is impossible to determine in advance which kind of treatment is more suitable for the individual patient.

Comparison of insulin regimens in patients with non-insulin-dependent diabetes mellitus

BACKGROUND

Insulin is widely used to improve metabolic control in patients with non-insulin-dependent diabetes mellitus (NIDDM), but there is no consensus about the optimal regimen of insulin treatment.

METHODS

We treated 153 patients with NIDDM for three months with five regimens: (1) oral hypoglycemic drug therapy plus NPH insulin given at 7 a.m. (the morning-NPH group), (2) oral hypoglycemic drug therapy plus NPH insulin given at 9 p.m. (the evening-NPH group), (3) NPH and regular insulin (ratio, 70 units to 30 units) given before breakfast and dinner (the two-insulin-injection group), (4) NPH insulin at 9 p.m. and regular insulin before meals (the multiple-insulin-injection group), and (5) continued oral hypoglycemic drug therapy (the control group).

RESULTS

The mean (+/- SE) value for glycosylated hemoglobin decreased similarly in all four insulin-treatment groups (1.7 +/- 0.3, 1.9 +/- 0.2, 1.8 +/- 0.3, and 1.6 +/- 0.3 percent, respectively). The decrease was significantly greater in these four groups than in the control group (0.5 +/- 0.2 percent; P < 0.001 vs. all insulin-treated groups). Weight gain was significantly less (1.2 +/- 0.5 kg) in the evening-NPH group than in the other insulin-treatment groups (2.2 +/- 0.5 kg in the morning-NPH group, 1.8 +/- 0.5 kg in the two-insulin-injection group, and 2.9 +/- 0.5 kg in the multiple-injection group; P < 0.05). In addition, the increment in the mean diurnal serum free insulin concentration was 50 to 65 percent smaller in the evening-NPH group than in the other insulin-treatment groups. Subjective well-being improved significantly more in the insulin-treatment groups than in the control group (P < 0.001).

CONCLUSIONS

In patients with NIDDM who are receiving oral hypoglycemic drug therapy, the addition of NPH insulin in the evening improves glycemic control in a manner similar to combination therapy with NPH insulin in the morning, a two-insulin-injection regimen, or a multiple-insulin-injection regimen, but induces less weight gain and hyperinsulinemia. The data thus suggest that patients with NIDDM do not benefit from multiple insulin injections and that nocturnal insulin administration appears preferable to daytime administration.