EL-Khuffash A, et al. Late medical therapy of patent ductus arteriosus using intravenous paracetamol. Archives of Disease in Childhood - Fetal and Neonatal Edition. 2015;100(3):F253-F6. (CoI statement: The authors of this paper are friends, colleagues and collaborators of mine), the effects of intravenous paracetamol on closing the PDA in infants who were being considered for PDA ligation are reported.
The dose was 60 mg/kg/day in four divided doses. Echos were done after 3 days of treatment and the course continued for a further 3 days if the PDA remained open.
Some of the background includes the fact that the 2 hospitals in Dublin don't give NSAID's during the first week of life, "due to the equivocal nature of the evidence regarding early PDA treatment" and don't give them after 3 weeks "where ibuprofen is not known to be effective" which doesn't give much time to use the 'standard' therapy. So of the 36 babies reported, 13 had never had ibuprofen as they were after 3 weeks, and 15 were said to have contra-indications (11 NEC, 3 IVH, and 1 thrombocytopenia, none of which I am sure are really contra-indications, but let's let that pass for now) only 8 had received ibuprofen (presumably a single course). The pre-paracetamol echo data show physically large PDAs, mean diameter of 3.3 mm, most babies had reverse diastolic flow in the abdominal aorta.
Nine of the babies had closure of their PDA after paracetamol, most of the others had a major constriction, and only 4 needed their PDA ligated in the end.
So if you have a very restricted use of ibuprofen, this is supportive data which shows that if you give IV paracetamol, many babies have closure of the PDA. Of course it doesn't tell you what happens to them if you don't give paracetamol, or if you give them ibuprofen. For that we, of course, need a prospective RCT.
As an aside, intravenous paracetamol is unfortunately unavailable in Canada, I'd really like to be able to give it... but as an analgesic!