Pharmaceutical companies will lose more than £40bn by 2019, due to patents on drugs expiring.

It is claimed companies such as Otsuka, Eli Lilly and AstraZeneca (AZ) will be affected the most, especially in the central nervous system (CNS) medication sector.

GlobalData analyst for healthcare industry dynamics, Adam Dion, said: “AZ’s CNS segment has been bleeding sales as a result of the company losing its patent on Seroquel, a treatment for bipolar disorder, allowing for cheaper generic alternatives.”

It is claimed AZ’s shares fell to 3% in 2013 from 9% in 2010.

Dion said Eli Lilly’s market share declined from 14.3% in 2010 to 11.2% in 2013, due to decreasing sales of the company’s medication for schizophrenia and bipolar disorder.

It is claimed Ablify, an anti-psychotic drug, produced by Otsuka, will have its US patent expire in 2015, meaning the drug is predicted to lose nearly £5bn by 2019 as a result of generic medications.