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PS-049 Pharmaceutical intervention to improve dose calculation of 4 mabs
  1. S Machado,
  2. M Rebelo,
  3. N Landeira,
  4. M Pereira
  1. Hospital Espirito Santo, Pharmacy, Evora, Portugal


Background The monoclonal antibodies (mAb) market has grown significantly in the past years. Worldwide sales will be nearly $125 billion by 2020. Cetuximab (Cet), trastuzumab (Tra), bevacizumab (Bev) and panitumumab (Pan) were the most used at our hospital. This represents 35% of the oncology department’s total expenditure.

Purpose To calculate mAb doses on the day of treatment, and to analyse differences between PD and CD, and the economic impact when PD >CD

Material and methods Patients’ weights with prescription of these mAb at the hospital were monitored over 4 months. Prescribed dose (PD)=dose prescribed by oncologist at the beginning of treatment. Calculated dose (CD)=weight based dose calculated by the pharmacist, according to the summary of product characteristics. CD was the dose actually administered to the patient (after authorisation by the head of the department). PD and CD were recorded and their differences were analysed. Using the drug’s average price (mg/€) cost savings where calculated when PD >CD (economic Impact=cost of PD – cost of CD).

Results mAb doses were calculated for 77 patients(n=367). PD=CD in 24% of total treatments. PD and CD were the same in 64% of treatments using Cet, 20% using Pan, 18% using Bev and 9% using Tra. Treatments with PD <CD (n=170) were more frequent. Cost savings were approximately €9527.

Conclusion Deviations from recommended dose were not significant. Study time may not have been enough to weight changes to reveal an impact on dose. Amount of cost savings of €9527 is an estimate. This cost review should have been done assessing number of vials consumed per patient. Analysis performed by Bai et al assessing either fixed or body weight based dosing would be superior in reducing pharmacokinetic (PK) variability. PK variability introduced by either dosing regimen is moderate relative to the variability generally observed in pharmacodynamics, efficacy and safety. Therefore, mAb dosing can be flexible. Given many practical advantages (error minimisation and easiest preparation), fixed dose might be a future approach.

References and/or acknowledgements BaiS, et al. A guide to rational dosing of monoclonal antibodies. Clin Pharmacokinetics2012;51:19–35.

No conflict of interest

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