Table 1.

Summary of the included studies

Study	Total (N)	Length of study	Constipation type	Baseline stool frequency (SD)	Concomitant laxative use	Age mean (SD) years	Gender (% male)	Polyethylene glycol formulation and daily dose	Polyethylene glycol (N)	Comparator and daily dose	Comparator (N)
Andorsky RI 1990 [12]	37	2 × 5 days	Chronic	87.5 % ≤ 2 stools/week	Continued use of fibre and bulk-forming agents. Laxatives or enemas for treatment failure: P = 12.5 %, C = 18.8 %	P1: 62	P1: 25 %	PEG3350 + E	High dose 16	Placebo	16
						P2: 58	P2: 19 %	High dose 16 oz	Low dose 16
								Low dose 8 oz
Attar A 1999 [13]	115	4 weeks	Chronic	Not specified	Suppositories, micro-enemas allowed. Any use: P = 16 %, C = 34 %	P: 55 (24)	P: 15 %	PEG3350 + E	60	Lactulose	55
						C: 55 (22)	C: 22 %	13–39 g		10–30 g
Awad RA 2010 [14]	47	30 days	Irritable bowel syndrome (IBS-C)	P: 1.3 (0.6)	Not allowed. P: 1 use of glycerine suppository	P: 30.7 (8)	12 %	PEG3350	23	Placebo	24
				C: 1.5 (0.7)	C: 1 use of enema	C: 36.5 (10)		10.35 g
Bouhnik Y 2004 [15]	65	28 days	Chronic, idiopathic	85 % < 3 stools/week	Suppositories, enemas allowed during washout, stopped 48 hours before baseline. 9 % of patients took concomitant treatment at study entry and all were stopped	57 (18)	14 %	PEG4000 10–30 g	32	Lactulose 10–30 g	33
Chapman RW 2013 [16]	139	28 days	Irritable bowel syndrome (IBS-C)	P: 1.28 (0.912)	Rescue medication bisacodyl if no bowel movement for 3 consecutive days. Mean No. weekly rescue doses: P = 0.30, C = 0.44	41.3 (14.8)	17 %	PEG3350 + E	68	Placebo	71
				C: 1.37 (0.849)				13.8–41.4 g
Chaussade S 2003 [17]	266	2 weeks	Chronic, idiopathic	P(H): 2.0 (0.9)	Rescue medication suppository if no bowel movement for 3 consecutive days. Stools post-suppository use were not included in study results	52.2 (18.5)	15 %	PEG3350 + E	High dose 69	PEG4000 High dose 20 g	High dose 67
				P(L): 2.2 (1.3)				High dose 11.8 g	Low dose 69	Low dose 10 g	Low dose 65
								Low dose 5.9 g
				C(H): 2.4 (1.7)
				C(L): 1.8 (1.0)
Cinca R 2013 [18]	240	2 weeks	Chronic	P: 0.7 (0.8)	Rescue medication ducosate micro-enema if no bowel movement for 3 consecutive days. Use of micro-enema: P = 0.8 %, C = 3.4 %	P: 40.0 (14.5)	0 %	PEG335 0 + E	120	Prucalopride 1–2 mg (serotonin [5-HT4] agonist)	116
				C: 0.7 (0.8)		C: 40.5 (13.2)		13.71–27.42 g
Cleveland MV 2001 [19]	23	2 × 2 weeks	History of constipation	2.6 (1.75)	Not allowed	47.7	4 %	PEG3350 10.35 g	23	Placebo	23
Corazziari E 1996 [20]	55	4 weeks	Chronic	P: 2.2 (0.5)	Rescue medication, laxatives if no bowel movement for 5 consecutive days. Use of laxatives: P = 16 %, C = 48 %	41.8 (14.8)	P: 32 %	PEG4000 + E 17.5 g	25	Placebo	23
				C: 1.9 (0.8)			C: 13 %
Corazziari E 2000 [21]	70	20 weeks	Chronic	P: 1.53 (1.35)	Rescue medication, laxatives if no bowel movement for 5 consecutive days. Use of laxatives was less frequent in PEG + E than placebo (P < 0.001)	43 (15)	17 %	PEG4000 + E 35 g	33	Placebo	37
				C: 1.29 (1.04)
Di Palma JA 1999 [22]	AM: 50 LT 35	10 days	Reported constipation	Not specified	Not allowed	AM: 36.2	AM: 6 %	PEG3350	AM high dose: 50	Placebo	AM: 50
						LT: 75.7	LT: 46 %	AM high dose: 34 g	AM low dose: 50		LT: 17
								AM low dose: 17 g	LT high dose: 17
								LT high dose: 12 g	LT low dose: 17
								LT low dose: 6 g
Di Palma JA 2000 [23]	151	14 days	History of constipation	Not specified	Not allowed	45.2	13 %	PEG3350 17 g	80	Placebo	71
Di Palma JA 2007A [24]	100	4 Weeks	Secondary to medications	Not specified	Fibre or other laxatives not allowed	58	26 %	PEG3350 17 g	46	Placebo	46
Di Palma JA 2007B [25]	304	6 months	Chronic	P: 86.5 % < 3 stools/week	Fibre not allowed. Rescue medication bisacodyl if no bowel movement for 4 consecutive days. Mean use of bisacodyl 5 mg: P = 2.8, C = 3.9 tablets/week	53	15 %	PEG3350 17 g	202	Placebo	100
				C: 94.4 % < 3 stools/week
Di Palma JA 2007C [26]	237	28 days	Chronic	100 % < 3 stools/week	Fibre not allowed. Rescue medication bisacodyl if no bowel movement for 4 consecutive days. Mean use of bisacodyl 5 mg: P = 1.4, C = 1.0 tablets/week	46	10 %	PEG3350 17 g	118	Tegaserod 12 mg (serotonin [5-HT4] agonist)	116
Freedman MD 1997 [27]	57	3 × 2 weeks	Opioid-induced	Not specified	Additional milk of magnesia or bisacodyl allowed. No difference in use between PEG + E and lactulose	Range 18–50	Not specified	PEG3350 + E 14 g	57	Placebo Lactulose 30 mL	Placebo 57
											Lactulose 57
Klauser AG 1995 [28]	8	2 × 6 weeks	Chronic	Median 3	Sodium picosulfate was allowed except for the last week of each study period. Median drops per day: P = 0, C = 4	46 (4)	0 %	PEG4000 60 g	8	Placebo	8
Seinela L 2009 [29]	65	4 weeks	Chronic functional	P: 9.3	Continued use of Plantago ovata seeds was allowed. Rescue medication bisacodyl 10 mg suppository if no bowel movement for 3 consecutive days. Use of suppositories: PEG + E = 12.5 %	86	34 %	PEG4000 + E 6–24 g	32	PEG4000 6–24 g	30
				C: 8.4
					PEG = 3.3 %
Wang H 2005 [30]	126	2 weeks	Chronic functional	P: 1.18 (0.77)	Not allowed	P: 51. 2 (14.8)	40 %	PEG3350 + E 27.6 g	63	Isphagula husk 7 g (bulk forming)	63
				C: 1.33 (0.68)		C: 50.0 (17.1)
Zangaglia R 2007 [31]	57	8 weeks	History of constipation amongst Parkinson’s Disease	P: 1.9 (0.56)	Rescue medication, rectal laxatives. Use of rectal laxatives: P = 4.3 % week 4 & 0 % week 8	71.0 (6.5)	60 %	PEG4000 + E 7.3–21.9 g	29	Placebo	28
				C: 2.0 (0.6)	C = 9.5 % week 4 & 12.5 % week 8

P Polyethylene glycol group, C Comparator group, AM Ambulatory healthy outpatients, LT Long term, H High dose, L Low dose