Other than a similar incidence of procedural pain in the 2 groups , the most common treatment-emergent adverse events , which were generally mild , were headache ( 14.6 % vs 12.0 % ) , constipation ( 8.3 % vs 10.0 % ) , and dizziness ( 6.3 % vs 8.0 % ) , for the palonosetron and ondansetron groups , respectively .