Kee 1989.

Methods	Double‐blind randomised controlled trial.
Participants	70 women recruited from a postpartum hospital ward in urban Singapore. Inclusion criteria: postpartum women with breast engorgement. Diagnosis of breast engorgement was based on some or all of the following: subjective complaint of pain in the breast and objective evidence of breast swelling, induration and impaired lactation.
Interventions	Intervention group (35 women): oral serrapeptase (Danzen), an anti‐inflammatory proteolytic enzyme drug derived from serratia E15 (isolated from the silk worm intestine) was administered in a dose of 2 tablets (5 mg per tablet) 3 times a day for 3 days. Control group (35 women) specially made tablets that were identical in appearance to the Danzen tablets were given according to the same regime. During the study breastfeeding was encouraged and concomitant breast massage and milk expression was allowed.
Outcomes	Total improvement of breast engorgement. Improvement of individual symptoms: ◦ improvement of breast induration; ∘ improvement of breast swelling; and ∘ improvement of breast pain.
Notes	The authors gave cumulative percentages in the results section, which the review authors corrected. The study authors reported that breastfeeding was encouraged during the study but they report that only 4 patients in the treatment group and 8 in the placebo breastfed their babies during the study period. No adverse reactions were reported by any of the patients given Danzen.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised controlled trial but random sequence generation not adequately described.
Allocation concealment (selection bias)	Unclear risk	Allocation concealment not defined.
Blinding (performance bias and detection bias) Women	Low risk	"The placebo tablets were specially manufactured for the study and were identical in appearance to Danzen tablets."
Blinding (performance bias and detection bias) Clinical staff	Low risk	"None of the research team was aware of the respective identification during the duration of the study."
Blinding of outcome assessment (detection bias)	Low risk	"An independent observer, unaware of the groups the patients were in, assessed each symptom and sign daily."
Incomplete outcome data (attrition bias) All outcomes	Low risk	The authors reported on all outcomes.
Selective reporting (reporting bias)	Low risk	The authors reported on all outcomes and all participants.
Other bias	Unclear risk	Role of sponsor unclear. Presumably provided tested drugs. Possible vested interest may have lead to a risk of bias in favour of tested drug.