Levels of coagulation FVIII and FIX at certain time points can be predicted using PKs
and studies have shown correlation between PK parameters and clinical phenotype in haemophilia. Using PK-tailored prophylaxis means that levels can be controlled, predicted and monitored to improve medical and health economic outcomes. In the near future, with the introduction of long-acting products, the use of PKs will become even more imperative. Population PKs have been studied for both FVIII and FIX and documented the requirement of sparse sampling only. This, together with new IT solutions, will soon make it feasible for haemophilia centres to use PKs in daily routine. PKs Veliparib cost are an important and integrated part of haemophilia treatment and have been for decades, even if always not fully evident. Strategies for replacement therapy have evolved. When concentrates for replacement therapy became available PCI-32765 in vitro during the 1950s and 1960s, treatment on demand was the dominating way of replacement. Some pioneers realised that haemorrhages and the sequelae of haemorrhages, mainly joint disease, could be prevented by implementing prophylaxis [10, 11] and regimens were more and more fine-tuned over the years – with prophylaxis being
started earlier and dosing being more frequent . Concomitantly with this evolution of regimens, the awareness of the role of PKs increased, as outlined in Fig. 1. Methods for PK evaluation have emerged and become more and more sophisticated. However, experiences from the 1970s clearly showed that if a specific number check details of units were infused three times per week, the
bleed prevention was much better than if infused once-weekly . The use of PKs has since become more established for prophylaxis not least by the contributions of Björkman and colleagues who, during the 1990s, showed the benefit of PK modelling and implementation during haemophilia prophylaxis . It stands clear from these early studies and several later studies that PKs introduce an understanding of how treatment is performed and how the concentrate behaves in the organism, all of benefit for the medical outcome and, not least, outcome in terms of cost efficacy. In other words, if PKs are not used, the patient is left to the discretion of opinion and not to evidence. The rationale for using PKs is that FVIII or FIX levels correlate with clinical phenotype. However, as always, there are exceptions from the rule, it has been clearly shown that levels do predict risk of bleeding. This was shown in a Swedish cohort where joints were not affected, that is, target joints did not impact the bleeding pattern , and later on by the studies of the large Advate® trials where Collins and colleagues clarified the role of factor levels for risk of bleeding in a well-controlled, large study  (Fig. 2).