OBJECTIVES: Immunosuppressive drugs (IS) are used in combination/schemes to achieve optimal regimen of immunosupression, increasing graft and recipient survival rates in post kidney transplant patients. The aim of this study is to determine immunosuppressant treatment patterns and associated costs in kidney transplant patients from the Brazilian National Transplant Program. METHODS: A review of the entire government administrative claim database (Outpatient Information System - SIA/DATASUS) was conducted from 2005 to 2008, to determine yearly expenses (in 2008 USD) with each IS combination. In order to assess the dynamics of the combinations used, a subset of this population, all patients from 7 hospitals who underwent kidney transplantation in 2004, was followed from January 2005 to December 2007 to estimate calcineurin inhibitors (CNI) switching rate and treatment adherence in terms of 24-month medication possession ratio (MPR). RESULTS: Analysis of the entire database reveals that overall IS expenses in kidney transplant patients more than doubled, from US$62,429,359 in 2005 to US$126,874,381 in 2008, mostly due to an increase in both treatment volume and costs from 2006 to 2007. From 2005 to 2007, monthly treatment volume increased 14.7% for cyclosporine and 62.9% for tacrolimus, whereas costs increased 3.2% for cyclosporine and 93.1% for tacrolimus. The highest financially impacting combination per CNI were tacrolimus plus mycophenolate sodium (US$37,329,606 in 2008), and cyclosporine plus mycophenolate sodium (US$10,163,990 in 2008). A total of 540 patients were eligible for the subpopulation analysis. CNI therapy switch rate, from tacrolimus to cyclosporine or vice-versa was 4.3% (n = 185). MPR for CNIs was 73.7% (n=224; SD=21.7%). CONCLUSIONS: From 2005 to 2008, IS drugs expenses in post kidney transplant patients substantially increased in Brazil. Low CNI switching rates suggests that de novo patients are the main target population for newer CNIs. The poor drug adherence detected is an important point of concern.