To determine the rates of parathyroidectomy in hemodialysis patients treated with either paricalcitol or cinacalcet.
A secondary cost analysis of the year following parathyroidectomy in the same patient group was also undertaken.
Study design and study population:
Retrospective observational cohort study involving incident users of paricalcitol or cinacalcet identified from a health care insurance database. The study excluded participants over the age of 64 because many would be covered by medicare in the US and the comparisons would loose validity. The cohort of patients was thus 2,704 about half of which received each drug. The comparator groups were mutually exlcusive – no subject could be receiving both agents. Analysis was limited to new prescriptions and to patients who received at least 30 days of medication.
While the groups were matched for age, there were more females in the cinacalcet group.. The patients in the paricalcitol group were deemed sicker in terms of comorbidies. Patients tended to be on dialysis longer before being prescribed cinacalcet than paricalcitol. About 10 – 15% of patients in each group had received other vitamin D receptor activators prior to receiving either paricalcitol or cinacalcet.
More patients in the cinacalcet group required a parathyroidectomy (2.24 per 100 pt yrs vs 0.58 per 100 pt yrs) than in the paricalcitol group. This translated into a 74% lower rate of parathyroidectomy in the group receiving paricalcitol.
In terms of the cost analysis portion of the study, as might be expected, there was an increase in inpatient costs during the parathyroidectomy procedure, but outpatient costs for the year before and after parathyroidectomy (excluding inpatient costs) were not different.
The study has a number of issues which limit its generalizability. The most obvious is the age cutoff – although younger people are more likely to require parathyroidectomy than their older counterparts. Counfounding by indication is also a major potential problem here. While it is true that vitamin D receptor activators may be prescribed for parathyroid hormone control, the data of the study from Teng et al (NEnglJMed 2003;349:446-456) provide a strong influence to prescribe these agents (and paricalcitol in particular) to patient who are unlikely ever to need a parathyroidectomy to control parathyroid hormone levels. Thus it is not too surprising that the authors found that patients were on dialysis longer before being prescribed cinacalcet than paricalcitol, nor that the paricalcitol group had lower parathyroidectomy rates. Further, froma biologic standpoint, cinacalcet is associated with hypocalcemia, which if not properly addressed would stimulate parathyroid hormone production, whereas the contrary is true of paricalcitol (albeit a lower risk of hypercalcemia than other vitamin D receptor activators such as calcitriol).
Impact on practice:
Both paricalcitol and cinacalcet are capable of controlling hyperparathyroidism to a degree. A proportion of patients will be resistant, and in this analysis at least, were more likely to be receiving cinacalcet. The data are unable to provide guidance to prescription because of a lack of biochemical observations. Impact on practice will be minimal
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