ibuprofen causes fluid retention so if he has fluid building up in his lungs, this would probably not be a good med.
also causes decreased blood flow to kidneys, it is more risky to use in the elderly, with heart or kidney disease or with diuretics such as lasix.
According to the rat care health book, the dose is 15 - 60 mg/Ib (15 - 60 mg/454.4 g) 2 - 4 times a day. Lower doses for analgesia, higher for inflammation.
At 40mg/454.4g he would need 51 mg of ibuprofen .... this would be approx. 1.27 ml at the strength of 40 mg/ml
Edit: I guess I'm too tired and in too much pain because the values in the rat guide don't make sense to me.
A kg is approx 2xs as much as a Ib so the amount for a kg should be twice as much as the amount for a Ib.
1 Ib = 454.4 g
Sorry but I'm not thinking clearly ... need more pain meds ...
all the best