Side effect: Constipation - Tramadol injection (33.7%), Morphin oral (75.9%), Morphin subcutaneous injection (82.6%), Morphin continuous subcutaneous infusion (91.3%), Fentanyl patch (14.5%).
Tác dụng phụ: Táo bón ở Tramadol tiêm (33,7%), Morphin uống (75,9%), Morphin TDD (82,6%), Morphin truyền DDLT (91,3%), Fentanyl dán (14,5%).