McKee 1990.

Methods	Parallel group RCT Location: USA Funding: not stated
Participants	Inclusion criteria: healthy children 2 to 5 years old, Frankl scale behaviour negative or definitely negative, failed non‐pharma management, requiring restorative treatment with LA and rotary instrument n = 60 Mean age (SE) in months: Group 1 (n = 15), 36.5 (2.7) Group 2 (n = 15), 41.7 (3) Group 3 (n = 15), 35.9 (2.7) Group 4 (n = 15), 43 ( 2.7)
Interventions	Group 1: placebo Group 2: meperidine (0.25 mg/lb) (approximately 0.11 mg/kg) Group 3: meperidine (0.50 mg/lb) (approximately 0.22 mg/kg) Group 4: meperidine (1 mg/lb) (approximately 0.45 mg/kg) All intramuscular, administered by "third party"
Outcomes	Modified Houpt, dichotomous behaviour scale, 10‐point behaviour scale, global rating scale, adverse effects
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Randomly assigned" ‐ method of sequence generation not described
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding ‐ Participant	Low risk	Quote: "Dentist, patient and research observer were unaware of treatment allocation"
Blinding ‐ Operator/sedationist	Low risk	Quote: "Dentist, patient and research observer were unaware of treatment allocation"
Blinding ‐ Outcome assessor	Low risk	Quote: "Dentist, patient and research observer were unaware of treatment allocation"
Incomplete outcome assessment	Low risk	Dropouts/aborted patients reported
Free of selective reporting	Low risk	All planned outcomes reported
Free of other bias	Low risk	No apparent differences between groups at baseline