Background: Darbepoetin-alpha is applicable at longer injection intervals. Our early experience in children on peritoneal dialysis suggested increased injection pain compared to epoetin-beta, possibly due to technical differences or patient anxiety.
Methods: To verify a possible difference in the painfulness of the injected fluids per se, we performed a prospective, randomized, double-blind trial in 13 paediatric end-stage renal disease patients. They received three injections of equivalent doses of darbepoetin-alpha or epoetin-beta in 0.6 ml saline, using neutral syringes and 27G needles, at 4 week intervals. Pain perception was recorded immediately and after 30 min on a visual analogue scale (VAS, 0 = no pain, 10 = maximal pain; complemented by 5 faces for young children).
Results: The patients perceived more intense immediate injection pain with darbepoetin-alpha than with epoetin-beta (5.4 +/- 1 vs 2.3 +/- 0.6, P < 0.05). This was confirmed by the impression of the parents (5.3 +/- 1 vs 2.0 +/- 0.9, P < 0.05) and the nurses (4.4 +/- 1 vs 2.2 +/- 0.6, P < 0.05). General injection pain was inversely related to patient age (R = -0.77, P = 0.001). Six patients perceived no or a mild difference in injection pain, whereas 7 subjects reported a markedly higher pain score (> or =4 VAS points) with darbepoetin-alpha. After 30 min, the injection site was largely painless with both drugs. No significant local reactions occurred with either medication (0.3 +/- 0.1 vs 0.3 +/- 0.1 on a 5-score scale).
Conclusions: Subcutaneous injections of darbepoetin-alpha are more painful than those of epoetin-beta in the majority of paediatric patients. The observed difference in painfulness is related to the nature of the injected compounds and may limit the subcutaneous applicability of darbepoetin-alpha in children.