OBJECTIVES: As Medicare Part D results in de facto centralization of buying power in the US, we hypothesized that NICE HTA's would increasingly influence the US market. The primary objective is to determine whether major findings of Health Technology Appraisals (HTAs) by the National Institute for Clinical Excellence (NICE; UK) impacted US trends in prescription volume, retail price and out-of-pocket costs of statins and of six therapeutic classes deemed medically necessary for Medicare beneficiaries.  As a point of reference, we sought to investigate the same market factors in relation to the index date of Medicare Part D introduction. METHODS: The two most prescribed statins (atorvastatin, simvastatin), anticonvulsants (clonazepam, gabapentin), antidepressants (escitalopram, fluoxetine), oral antineoplastics (capecitabine, imatinib), antipsychotics (quetiapine, risperidone), immunosuppressants (azathioprine, mycophenolate), and antiretrovirals (emtricitabine/tenofovir, ritonavir) were selected based on total prescriptions (TRx).  TRx, average retail price (ARP) and average out-of-pocket costs (OPC) per prescription were collected quarterly for 2005-2008.  For six related HTAs conducted by NICE and the implementation of Medicare Part D, TRx, ARP and OPC were analyzed for the same number of quarters before and after the index event.  Parameters were collected using Verispan’s VONA and VOPA databases. Statistical analyses were performed using one-way ANOVA.  RESULTS: From 2005 to 2008, 7 of the 14 drugs analyzed were directly or indirectly covered by a NICE HTA.  Two HTAs were correlated with a significant increase in TRx, four with a significant increase in ARP, and two with a significant increase in OPC (p<0.05).  By comparison, Medicare Part D resulted in significant TRx increases for ten drugs (and no decreases), eight showed ARP increases and two had ARP decreases (p<0.05).  Interestingly, seen drugs decreased OPC while two increased (p<0.05).CONCLUSIONS: NICE HTAs had mild effects on the prescription utilization and costs in the US, while Medicare Part D caused fundamental changes to the market parameters measured. The influence of NICE decisions on the US market should be monitored as HTAs are expected to play a more significant role in the advent of Medicare Part D Reimbursement.