1. Summary of included studies.
| Study | Country | Number of participants | Low‐/high‐risk pregnancy | Gravidity of participants | Time of intervention | Intervention (dose and route of administration) | Control | Non‐study interventions | Induced/spontaneous labour |
| Ajmera 2006 | India | 225 | Low risk | Primi‐and multigravidas | Active phase, 3 cm dilatation | Drotaverine hydrochloride (40 mg IMI¹) Valethamate bromide (8 mg IVI²) |
No medication | None specified | Spontaneous |
| Al Matari 2007 | Saudi Arabia | 199 | Not mentioned | Not mentioned | Not mentioned | Hyoscine‐N‐butyl bromide (not mentioned) | Placebo (not specified) | None specified | Not mentioned |
| Al Qahtani 2011 | Saudi Arabia | 110 | Low risk | Primigravidas | Established labour, 3‐4 cm dilatation | Hyoscine butyl bromide (40 mg IMI) | NaCl³ 0.9% (2 mL IMI) | Amniotomy, opioid analgesia | Spontaneous |
| Azari 2010 | Iran | 200 | Not mentioned | Primigravidas | 4 cm dilatation and ruptured membranes | Hyoscine and atropine (20 mg IVI) | Dextrose water (2 cc IVI) | Not specified | Not mentioned |
| Batukan 2006 | Turkey | 100 | Low risk | Primi‐and multigravida | 4‐5 cm dilatation | Valethamate bromide (8 mg IMI) | NaCl 0.9% (1 mL IVI) | Oxytocin if necessary, amniotomy if no spontaneous ROM⁴ at 8‐10 cm | Spontaneous and induced |
| Cromi 2011 | Italy | 120 | Low risk | Primigravida | 3‐5 cm dilatation | Rociverine (20 mg IMI) | NaCl 0.9% (2 mL IMI) | Amniotomy, augmentation with oxytocin, epidural analgesia | Spontaneous |
| Dahal 2013 | Nepal | 300 | Low risk | Primi‐ and multigravidas | Unclear | Valethamate bromide (8mg IMI) Drotaverine hydrochloride (40mg IMI) |
No medication | Amniotomy once cervical dilatation > 4cm, or if Bishop's score was favourable, oxytocin augmentation | Spontaneous and induced |
| Gupta 2008 | India | 150 | Low and high risk | Primi‐and multigravidas | 3 cm dilatation | Drotaverine hydrochloride (40 mg IMI) Hyoscine butyl bromide (20 mg IVI) |
No medication | Oxytocin if necessary, amniotomy | Not specified |
| Khosla 2003 | India | 300 | Low risk | Primi‐and multigravidas | 4 cm dilatation | Valethamate bromide (8 mg IMI) Drotaverine hydrochloride (40 mg IMI) |
No medication | Not specified | Spontaneous |
| Kuruvila 1992 | India | 120 | Low risk | Primi‐ and multigravidas | 2‐4 cm | Valethamate bromide (8 mg IMI) | NaCl 0.9% (1 mL IMI) | Oxytocin if necessary, amniotomy, pethidine 75 mg for primigravidas) | Not specified |
| Madhu 2010 | India | 150 | Low risk | Primi‐and multigravida | 4 cm dilatation | Drotaverine hydrochloride (40 mg IMI) Valethamate bromide (8 mg IMI) |
NaCl 0.9% (2 mL IMI) | Amniotomy, oxytocin if required, paracetamol and pethidine for labour analgesia | Spontaneous |
| Makvandi 2010 | Iran | 130 | Low risk | Primigravidas | 3‐4 cm dilatation | Hyoscine butyl bromide (20 mg PR⁵) | Placebo suppository | Amniotomy when presenting part was fixed | Spontaneous |
| Mukaindo 2010 | Kenia | 85 | Low risk | Primigravidas | 3‐6 cm dilatation | Hyoscine butyl bromide (40 mg IVI) | Sterile water (2 mL IVI) | Amniotomy and augmentation with oxytocin as per protocol | Spontaneous |
| Raghavan 2008 | India | 150 | Not mentioned | Primigravidas | Not mentioned | Hyoscine butyl bromide (PR) Valethamate bromide (IVI) |
No medication | Not specified | Spontaneous |
| Samuels 2007 | Jamaica | 129 | Low risk | Primi‐ and multigravidas | 4‐5 cm dilatation | Hyoscine butyl bromide (20 mg IVI) | NaCl 0.9% (1 mL IVI) | Routine amniotomy, opioid analgesia, oxytocin | Spontaneous |
| Sekhavat 2012 | Iran | 188 | Low risk | Multigravidas | 3‐4 cm dilatation | Hyoscine butyl bromide (20 mg IVI) | NaCl 0.9% (1 mL IVI) | Amniotomy, oxytocin | Spontaneous |
| Sharma 2001 | India | 150 | Low risk | Primigravidas | 4 cm dilatation | Drotaverine hydrochloride (40 mg IMI) Valethamate bromide (8 mg IMI) |
No medication | None | Spontaneous |
| Singh 2004 | India | 100 | Low risk | Primigravidas | 3‐6 cm dilatation | Drotaverine hydrochloride (40 mg IMI) | Distilled water 2 mL (IMI) | Amniotomy, oxytocin, pentazocine and promethazine, episiotomy | Spontaneous |
| Taskin 1993 | USA | 120 | Low risk | Primi‐and multigravidas | 4‐5 cm dilatation | Valethamate bromide (8 mg IVI) Hyoscine bromide (20 mg IVI) Meperidine (50 mg IVI) |
Placebo (not specified, IVI) | Not specified | Not mentioned |
| Warke 2003 | India | 100 | Low risk | Primigravidas | 3 cm dilatation | Camylofin dihydrochloride (50 mg IMI) | Placebo (not specified (IMI) | None | Spontaneous |
| Yilmaz 2009 | Turkey | 160 | Low risk | Primigravidas | 4‐6 cm dilatation | Valethamate bromide (16 mg IVI) Meperidine (50 mg IVI) |
NaCl 0.9% (10 mL) | Amniotomy, oxytocin, episiotomy | Induced only |
¹IVI: intravenous injection
²IMI: intramuscular injection
³NaCl: sodium chloride/saline
⁴ROM: rupture of membranes
⁵PR: per rectum