Side effect: Constipation - Tramadol injection (25.6%), Morphin oral (74.5%), Morphin subcutaneous injection (83.3%), Morphin continuous subcutaneous infusion (91.3%), Fentanyl patch (14.5%).
Tác dụng phụ: Táo bón ở Tramadol tiêm (25,6%), Morphin uống (74,5%), Morphin TDD (83,3%), morphin truyền DDLT (91,3%), Fentanyl dán (14,5%).