Adding to the evidence in rheumatoid arthritis, the risk of herpes zoster is high especially among bDMARD and cyclophosphamide users in a heterogeneous, population-based Australian cohort.
The study comprised 254,065 participants in the Sax Institute’s 45 and Up Study and linked data from the PBS, hospital records and deaths registry.
It found 2.4% of participants had used DMARDs before their recruitment date and 2.5% were new users.
Of new users, 87.3% were only dispensed csDMARDs, 3.0% were only dispensed bDMARDs and 11.7% were dispensed both csDMARDs and bDMARDs.
The most commonly prescribed csDMARD during follow-up was methotrexate (28.4%) and the most commonly prescribed bDMARD was rituximab (27.5%).
The University of NSW study, published in Rheumatology, found 6.7% of participants had a first zoster event during follow-up.
Participants using bDMARDs, either alone or in combination with csDMARDs, had an increased risk of zoster (aHR 2.53 [95%CI 2.03-3.16]) compared to those only using csDMARDs (aHR 1.48 [95%CI 1.33-1.66]).
“This increased risk of zoster associated with bDMARD compared to csDMARD users was consistently observed in participants aged <65 and ≥65 years and in men and women,” the study said.
However the limited numbers of people using bDMARDs meant the study could not examine zoster risk by drug.
The highest zoster risk in csDMARD users was seen in those who exclusively used cyclophosphamide (aHR 2.69 [95%CI 1.89-3.83] compared to more moderate risk in hydroxychloroquine (aHR 1.43 [95%CI 1.11-1.83]) and azathioprine users (aHR 1.57 [95%CI 1.07-2.30]).
Zoster risk was not elevated in users of methotrexate (aHR 1.24 [95%CI 0.98-1.57]), sulfasalazine (aHR 1.00 [95%CI 0.71-1.42]) and leflunomide (aHR 0.41 [95%CI 0.06-2.88]).
The study noted that cyclophosphamide, the highest risk csDMARD, remained a treatment of choice in severe SLE, vasculitis and other severe autoimmune diseases while hydroxychloroquine was commonly prescribed as first-line therapy in RA and SLE.
“Given increasingly widespread use of DMARDs and the increased zoster risk found in DMARD users, particularly those receiving bDMARDs, but also for those using csDMARDs including hydroxychloroquine, it is important that clinicians are aware of the risks so that patients can be alerted for the potential occurrence of zoster and prompt antiviral therapy can be given,” they said.
“Also, zoster vaccine is another possible preventative strategy.”
They said the live-attenuated vaccine was recommended to be administered at least 1 month before the commencement of DMARD treatment which was not always feasible.
Instead the non-live zoster vaccine (Shingrix) which is licensed for people aged ≥50 years including immunocompromised individuals might be more promising for DMARD users.