Background Telaprevir is used in the treatment of chronic hepatitis C (HCV).

Purpose To find out at what point adverse reactions (ADRs) appear from the start of telaprevir treatment in order to prevent harm and improve management.

Materials and methods Retrospective observational study. HCV genotype-1 patients were included who had completed telaprevir treatment in our Health Department.

Severity of ADRs detected was classified according to the SPC.

We measured:

• – Time to appearance of ADRs: time from the start of triple therapy until the appearance of ADRs including all grades.

• – Time to appearance of higher grade ADRs: time from start of treatment until the appearance of higher grade ADRs.

• – Time to need supportive treatment: time from start of treatment until the prescription of exogenous erythropoietin or colony stimulating factors.

Results 68 patients (76% male) were included with an average age of 52.3 ± 8.7 years old.

ADRs including all grades: thrombocytopenia (76.5%), anaemia (60.3%), neutropenia (55.9%), hyperuricaemia (52.9%), hyperbilirubinaemia (39.7%), lymphopenia (38.2%) and raised creatinine (4.4%).

29.4% of patients required exogenous erythropoietin and 1.5% granulocyte colony stimulating factors.

Time to appearance of ADRs: 33 days (13–80) for anaemia, 31 (7–82) neutropenia, 35 (11–76) lymphopenia, 27 (10–69) thrombocytopenia, 31 (14–82) hyperuricaemia, 43 (16–70) increased creatinine, and 32 (15–77) hyperbilirubinaemia.

Time to appearance of more severe ADRs: 56 days (27–82) for anaemia, 46 (7–82) neutropenia, 53 (17–82) lymphopenia, 30 (10–82) thrombocytopenia, 57 (16–82) hyperuricaemia, 66 (62–70) increased creatinine, and 36 (15–77) hyperbilirubinaemia.

Time to supportive treatment needed: 57 days (22–82) for erythropoietin, and 22 for colony stimulating factors.

Conclusions The study shows an early appearance of thrombocytopenia and the highest grade of hyperbilirubinaemia. It took longer for the maximum degree of toxicity to appear in other ADRs. Time to erythropoietin treatment corresponded well with the appearance of more severe anaemia.

Knowing when ADRs are likely to appear can help us design early intervention strategies to improve patient safety.

No conflict of interest.