Hematocrit stability following intravenous versus subcutaneous administration of epoetin alfa to dialysis patients: a post hoc analysis.
BACKGROUND, SUBJECTS AND METHODS: A previous study of epoetin alfa dose requirements [Paganini et al. 1995] among hemodialysis patients who were switched from thrice weekly intravenous (i.v.) to thrice weekly subcutaneous (s.c.) administration showed that the weekly epoetin alfa dose requirement decreased by 18.5% after 13 to 16 weeks s.c. treatment and 26.5% after 21 to 24 weeks, without significant change in hematocrit. There was patient-to-patient variation in response, however, and 39% of the patients required the same or greater doses of epoetin alfa after the change from i.v. to s.c. administration. The present study reexamines the database to compare hematocrit stability between the two routes of administration.


RESULTS
During 4 weeks of i.v. epoetin alfa administration, the pooled standard deviation (SD) for the patients' (n = 72) weekly hematocrit measurements was 1.40, compared with weeks 13 to 16 of s.c. epoetin alfa administration when the SD was 1.66 (p < 0.01). Among 41 patients who completed 24 weeks of s.c. therapy, the pooled SD for the 4 weeks of i.v. treatment was 1.37 compared with 2.02 during weeks 21-24 of s.c. treatment (p < 0.01). Sixty-eight percent of patients had lower hematocrit SD during 4 weeks of i.v. therapy than during the 4 weeks of s.c. therapy (p = 0.03).


CONCLUSIONS
These data suggest that hematocrits may be more stable when epoetin alfa is administered i.v. rather than s.c. to patients on dialysis. These results would be expected since 100% of i.v.-administered epoetin alfa reaches the systemic circulation compared with 18% to 80% bioavailability of s.c.-administered epoetin alfa. Within-patient variation in s.c. epoetin alfa absorption may be related to non-uniformity of adipose tissue, blood supply, lymphatic drainage, and other factors at sequential injection sites, and may explain the variability in hematocrit after s.c. administration.
Goodkin
D A
DA
Amgen Inc., Thousand Oaks, CA 91320-1789, USA.
Gimenez
L F
LF
Graber
S E
SE
Van Stone
J C
JC
Egrie
J C
JC
Okamoto
D M
DM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001682:Biological Availability; D000068817:Epoetin Alfa; D004921:Erythropoietin / Q000008:administration & dosage*; D006397:Hematinics / Q000008:administration & dosage*; D006400:Hematocrit; D006801:Humans; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D008875:Middle Aged; D011994:Recombinant Proteins; D006435:Renal Dialysis
D006397:Hematinics; D011994:Recombinant Proteins; D004921:Erythropoietin; D000068817:Epoetin Alfa