Intervention(s) (route, frequency, total dose/day)	Comparator(s) (route, frequency, total dose/day)
Avilés 1999	Insulin as before treatment of at least 50 U insulin/day + metformin, oral, 2500 mg/day, 5 tablets of 500 mg daily	Insulin as before treatment of at least 50 U insulin/day + placebo, 5 tablets daily
Barnett 2013	Insulin (premixed 67.4%, intermediate 16.8%, long‐acting 11.6%, intermediate + long‐acting 1.1%, intermediate + premixed 1.1, long‐acting + premixed 1.1) 53.6 U (range 30‐150) daily dose + saxagliptin, oral, 5 mg daily	Insulin (premixed 54.3%, intermediate 21.7%, long acting 13.0%, intermediate + long‐acting 6.5%, intermediate + premixed 4.3, long‐acting + premixed 0) 55.3 U (range 30‐149) daily dose + placebo daily
Casner 1988	NPH insulin twice a day, total of at least 25 U insulin/day + glibenclamide, oral, 3.39 ± 0.22 mg/day	NPH insulin twice a day, total of at least 25 U insulin/day + placebo, oral, 3.28 ± 0.28 mg/day
Chiasson 1994	Insulin (type and dose not mentioned) + acarbose, oral, 3 times a day, 50 mg to 200 mg/day	Insulin (type and dose not mentioned) + placebo, oral, 3 times a day
Coniff 1995	Insulin (type and dose not mentioned) + acarbose, oral, 3 times a day 50 mg to 300 mg/day	Insulin (type and dose not mentioned) + placebo, oral, 3 times a day
Feinglos 1998	Insulin (regular or NPH: 1 participant; daily, 26 participants; twice a day, 2 participants: 3 times a day, dose not mentioned) + glipizide, oral, 5‐40 mg/day, daily or twice a day	Insulin (regular or NPH: 1 participant; daily, 26 participants twice a day, 2 participants 3 times a day, dose not mentioned) + placebo, oral
Fonseca 2007	Injectable insulin (type not mentioned) of at least 30 U/day + vildagliptin, oral, 100 mg/day, twice a day 50 mg	Injectable insulin (type not mentioned) of at least 30 U/day + placebo, oral, twice a day
Fritsche 2000	NPH insulin twice a day (dose not mentioned) + metformin, oral, daily 850 mg ‐ 3 times a day	NPH insulin twice a day (dose not mentioned) + placebo, oral, daily ‐ 3 times a day
Giugliano 1993	Regular and lente insulin, mean dose 90 (9 SD) U/day, twice a day + metformin, oral, 850 mg twice daily	Regular and lente insulin, mean dose 90 (9 SD) U/day, twice a day + placebo, oral, twice daily
Groop 1985	Insulin (type and dose not mentioned) + glibenclamide, oral, 10 mg/day, twice a day 5 mg	Insulin (type and dose not mentioned) + placebo, oral, twice a day
Hermann 2001	Insulin (rapid‐acting + NPH or premixed) 0.75 (0.28 SD) U/kg/day + metformin, oral, 2 weeks daily 850 mg, thereafter twice a day 850 mg	Insulin (rapid‐acting + NPH or premixed) 0.73 (0.23 SD) U/kg/day + placebo, oral, 2 weeks daily, thereafter twice a day
Hirsch 1999	Insulin (type and dose not mentioned) + metformin, oral, 2.5 gram/day, frequency not stated	Insulin (type and dose not mentioned) + placebo, oral, frequency not stated
Hong 2012	Insulin (glargine, glargine + rapid‐acting, NPH + regular) at least 10 U/day + sitagliptin, oral, 100 mg/day	Increase insulin (glargine, glargine + rapid‐acting, NPH + regular) by ≥ 10% at random at the start of the intervention and again by ≥ 10% at 12 weeks if their HbA1c was not within target (≤ 7%) If glargine insulin 20 U daily was used, the dose increased to ≥ 22 U daily and to ≥ 24 U daily at 12 weeks. If 20‐10 U mixed insulin was used twice a day, the dose was increased to ≥ 22‐11 U twice a day and ≥ 24‐12 U twice a day at 12 weeks
Kitabchi 1987	Insulin (NPH, dose not mentioned) + tolazamide, oral, 1000 mg/day, twice a day 500 mg	NPH insulin alone
Krawczyk 2005	Insulin (type not mentioned) 57.5 (15.8 SD) U + metformin 1500 mg once daily	Insulin alone (type not mentioned) 59.5 (15.4 SD) U
Kyllastinen 1985	Insulin (type not mentioned) mean dose 58 (3 SD) U daily + glibenclamide, oral, 10 mg/day, twice a day 5 mg	Insulin (type not mentioned) mean dose 58 (3 SD) U daily + placebo, oral, twice daily
Lewitt 1989	Insulin (14 participants on daily, 17 on twice a day, 12 mixed, 19 premixed or intermediate‐acting insulin) mean dose 47 (21 SD) U + glibenclamide, oral, 15 mg/day, 10 mg in the morning and 5 mg in the evening	Insulin (14 participants on daily, 17 on twice a day, 12 mixed, 19 premixed or intermediate‐acting insulin) mean dose 47 (21 SD) U + placebo, oral, twice daily
Lindström 1999	Soluble insulin (total dose 100 U/ml 3 times a day) + intermediate‐acting insulin (100 U/ml daily) + glibenclamide, oral, 10.5 mg/day, 3 times daily 3.5 mg	Soluble insulin (total dose 100 U/ml three times a day) + intermediate‐acting insulin (100 U/ml daily) +placebo, oral 3 times daily
Longnecker 1986	Insulin (5 participants daily insulin injection: 1 participant on isophane insulin suspension alone (40 U daily), 4 participants on isophane insulin suspension (48 (8 SD) U) + regular insulin injections (23 (9 SD) U); 6 participants twice a day insulin injections: mean morning dose 38 (6 SD) U (regular, isophane suspension, or both) + mean afternoon dose 25 (7 SD) U (regular, isophane suspension, or both) + tolazamide, oral, 1000 mg, twice daily 250 mg	Insulin (5 participants daily insulin injection: 1 participant on isophane insulin suspension alone (40 U daily), 4 participants on isophane insulin suspension (48 (8 SD) U) + regular insulin injections (23 (9 SD) U); 6 participants DIB insulin injections: mean morning dose 38 (6 SD) U (regular, isophane suspension, or both) + mean afternoon dose 25 (7 SD) U (regular, isophane suspension, or both) + placebo, oral, twice daily
Mattoo 2005	Insulin (type and dose not mentioned) + pioglitazone 30 mg	Insulin (type and dose not mentioned) + placebo, oral
Mauerhoff 1986	Usual insulin (type and dose not mentioned) + Hb420 (galenic form of glibenclamide) 7 mg before breakfast and 3.5 mg before supper	Usual insulin (type and dose not mentioned) + placebo, oral
Mezitis 1992	Biosynthetic human insulin (dose not mentioned) + glibenclamide, oral, twice daily 2 tablets (dose not mentioned)/day	Biosynthetic human insulin + placebo, oral
Mudaliar 2010	Insulin (type and dose not mentioned) + pioglitazone, oral, 30 mg for 4 weeks, then titrated to 45 mg	Insulin (type and dose not mentioned) + placebo, oral
Nemoto 2011	Insulin (type and dose not mentioned) + miglitol, oral, 50 mg 3 times a day	Insulin (type and dose not mentioned) + placebo, oral, 3 times a day
Osei 1984	Insulin (intermediate‐acting insulin alone or in combination with short‐acting insulin twice a day (dose not mentioned)) + glibenclamide, oral, 5‐20 mg once daily	Insulin (intermediate‐acting insulin alone or in combination with short‐acting insulin twice a day (dose not mentioned)) + placebo, oral
Quartraro 1986	Monocomponent porcine insulin (mean dose 95 (2 SD) U daily) + gliclazide 40‐240 mg once daily	Insulin alone (mono component porcine insulin (mean dose 95 (2 SD) U daily))
Reich 1987	Insulin (intermediate‐acting, dose not mentioned) + glibenclamide, oral, 5‐40 mg once daily	Insulin (intermediate‐acting, dose not mentioned) + placebo, oral
Relimpio 1998	Insulin (premixed formulation of soluble and NPH or NPH only, twice a day in 23 participants and 3 times a day in 1 participant) + metformin 1275‐2550 mg once daily	Insulin dose increase (premixed formulation of soluble and NPH or NPH only, twice a day in 22 participants and 3 times a day in 1 participant), insulin increase by 10%
Robinson 1998	Trial 1: insulin (type and dose not mentioned) + metformin 1000 mg/day increasing to 2000 mg /day	Insulin (type and dose not mentioned) + placebo
Rosenstock 2002	I1: insulin (type and dose not mentioned) + pioglitazone 15 mg once daily	Insulin (type and dose not mentioned) + placebo once daily
	I2: insulin (type and dose not mentioned) + pioglitazone 30 mg once daily
Schade 1987	Insulin (intermediate‐acting or short‐acting) mean dose at least 28 U/day (daily or twice a day) + glibenclamide 20 mg once daily	Insulin (intermediate‐acting or short‐acting, mean dose at least 28 U/day, daily or twice a day) + placebo, oral
Schiel 2007	I1: insulin glargine (before treatment dose) + glimepiride 3 mg/day	Insulin alone (75/25 or 70/30 premixed human insulin)
	I2: insulin glargine (before treatment dose) + glimepiride 3 mg/day + metformin 1700 mg/day
Simpson 1990	Usual insulin soluble + isophane twice a day or soluble + zinc‐complexed insulin daily or twice a day) + glipizide 10 mg twice a day	Usual insulin soluble + isophane twice a day or soluble + zinc‐complexed insulin daily or twice a day) + placebo, oral
Stenman 1988	Insulin (intermediate‐acting daily or twice a day or intermediate‐ and short‐acting daily) + glibenclamide, oral, 15 mg once daily	Insulin (intermediate‐acting daily or twice a day or intermediate‐ and short‐acting daily) + placebo, oral
Strowig 2002	I1: insulin (type and dose not mentioned) + metformin, oral, 2000 mg once daily	Insulin alone (type and dose not mentioned)
	I2: insulin (type and dose not mentioned) + troglitazonea, oral, 600 mg once daily
Wulffelé 2002	Insulin (Actrapid + Insulatard 4 times daily or mixed Actrapid (10%‐50%) + Insulatard (90%‐50%) twice a day) + metformin, oral, 3 x 850 mg once daily	Insulin (Actrapid + Insulatard 4 times daily or mixed Actrapid (10%‐50%) + Insulatard (90%‐50%) twice a day) + placebo, oral
Yilmaz 2007	I1: insulin (mixed 30% insulin aspart + 70% NPH insulin twice a day) + acarbose, oral, 300 mg once daily	Insulin alone (mixed 30% insulin aspart + 70% NPH insulin twice a day)
	I2: insulin (mixed 30% insulin aspart + 70% NPH insulin twice a day) + metformin, oral, 1700 mg once daily
	I3: insulin (mixed 30% insulin aspart + 70% NPH insulin twice a day) + rosiglitazonea, oral, 8 mg once daily
aoff the market I: intervention; NPH: Neutral Protamine Hagedorn; SD: standard deviation; U: units