Cetirizine Matches Clemastine Against Paclitaxel Reactions With Far Less Sedation

A prospective observational study across three Dutch hospitals has found that oral cetirizine prevented paclitaxel hypersensitivity reactions just as effectively as intravenous clemastine, while producing dramatically fewer sedative side effects. Among 100 women with breast cancer, the incidence of hypersensitivity reactions during the first two paclitaxel doses was identical in both groups at 8 percent, yet premedication-related adverse events struck 80 percent of patients receiving clemastine compared with only 10 percent of those taking cetirizine. The findings, published in Drugs & Therapy Perspectives, support a simpler, more patient-friendly approach to premedication before one of the most widely used chemotherapy drugs in breast cancer care.

Paclitaxel, first isolated in the early 1960s from the bark of the Pacific yew tree and designated an essential medicine by the World Health Organization in 2019, is effective against breast, lung, and gynecological cancers. But the drug is dissolved in a mixture of 50 percent ethanol and 50 percent polyoxyethylated castor oil, and this formulation is linked to hypersensitivity reactions during infusion. These reactions, typically type I allergic responses, can involve erythroderma, chest and back pain, bronchospasm, and dangerous swings in blood pressure, and in rare cases can become life-threatening. Most occur during the first two paclitaxel doses and are thought to arise from a multifactorial process involving direct stimulation of mast cells and basophils, complement activation, and IgE-mediated responses.

To reduce this risk, prophylactic premedication has long been standard practice, traditionally combining three drugs: the corticosteroid dexamethasone, a histamine-1 receptor antagonist, and a histamine-2 receptor antagonist such as ranitidine. This empirically derived regimen reduced the incidence of severe hypersensitivity reactions from roughly 25 to 30 percent down to 2 to 4 percent. However, the first-generation antihistamines commonly used, including clemastine and diphenhydramine, cross the blood-brain barrier and frequently cause sedation, drowsiness, and anticholinergic effects. Clemastine in particular exhibits potent anticholinergic activity. Second-generation antihistamines such as cetirizine penetrate the brain far less and therefore carry a more favorable safety profile.

The new study was motivated in part by sustainability guidance from the European Society for Medical Oncology’s Climate Change Task Force, which suggested substituting intravenous clemastine with oral cetirizine. Because cetirizine can be taken at home, the substitution could reduce adverse effects while also cutting chair time, lowering workload in oncology departments, and reducing costs. Earlier studies of such substitutions had suggested comparable efficacy with better tolerability, but most were limited by small samples, retrospective designs, or the absence of a control group. The Dutch team set out to strengthen the evidence with a prospective, parallel-arm comparison.

Researchers at Isala Hospital in Zwolle, Radboud University Medical Center in Nijmegen, and Deventer Hospital enrolled 100 consecutive female patients between May 2023 and March 2025. All were scheduled to receive four cycles of dose-dense doxorubicin and cyclophosphamide followed by weekly paclitaxel at 80 milligrams per square meter for 12 doses. Fifty patients, treated at Isala, took 10 milligrams of oral cetirizine at home one hour before infusion, alongside oral dexamethasone the evening and morning before. The other fifty, treated at the two other hospitals, received 2 milligrams of intravenous clemastine 30 minutes before paclitaxel, together with intravenous dexamethasone at doses that varied by institution. Based on the ESMO task force guidance, an H2-antagonist is no longer part of Dutch paclitaxel premedication regimens.

Hypersensitivity reactions during the first two paclitaxel doses were graded using CTCAE version 5.0, and premedication side effects were captured through a structured questionnaire administered by oncology nurses in real time. In the cetirizine cohort, four patients, or 8 percent, experienced a hypersensitivity reaction. In the clemastine cohort, six reactions occurred in four patients, also 8 percent, because two patients reacted at both doses. Most reactions were grade 1, with three grade 2 reactions split between the groups, and no severe reactions were observed. No patient had to discontinue treatment because of a reaction. Median age was 51 years in the cetirizine group and 55 in the clemastine group, a non-significant difference.

The safety contrast was stark. Five patients in the cetirizine cohort, 10 percent, reported adverse events at one or both doses, compared with 40 patients, 80 percent, in the clemastine cohort. Sedation and drowsiness dominated in both groups, with sedation most frequent among clemastine recipients and drowsiness most frequent among cetirizine recipients. Patients who experienced side effects often reported more than one, and most who had them did so at both doses. A reported food or medication allergy, more common in the clemastine group, was not correlated with the likelihood of a hypersensitivity reaction in this cohort, consistent with the inconsistent findings of earlier studies. Stratified analyses accounting for differences in dexamethasone dosing across the three hospitals did not change the primary outcome.

Beyond tolerability, the researchers highlighted practical gains. First-generation antihistamines are known to impair driving ability and increase the risk of falls, injuries, and fatal accidents through sedation and reduced cognitive performance. Patients with fewer sedative effects are more likely to travel to the hospital independently, reducing the need for caregiver accompaniment during weekly visits. Eliminating the pre-infusion intravenous clemastine cut chair time by approximately one hour per treatment session, benefiting patients, caregivers, and healthcare providers alike. The authors note that similar advantages may extend to other orally administered second-generation antihistamines, as has been suggested for loratadine, though the availability of specific agents may not be universal.

The study has limitations the authors acknowledge openly. No formal statistical power calculation was performed, and the team of fifty patients per cohort, while among the largest in this substitution literature, remains small in absolute terms. A very large randomized trial would be needed to formally prove noninferiority. The observational design compared institutional protocols rather than randomly assigning treatment, and institutional differences in dexamethasone dosing and patient populations could have influenced results, although the homogeneous restriction to women with breast cancer receiving an identical weekly paclitaxel schedule minimized confounding. Using a prospective control group rather than a historical cohort also reduced reporting bias, since side effects are often underestimated in retrospective chart reviews.

Interestingly, the low hypersensitivity rate observed contrasts with the high rates of 25 to 30 percent reported in early paclitaxel studies, and the authors speculate that advances in paclitaxel formulation over recent decades may partly explain why recent premedication de-escalation studies consistently find low reaction rates. Several studies have already shown that omitting the H2-antagonist does not appear to increase risk, and the feasibility of omitting dexamethasone entirely is currently under evaluation. Nevertheless, product labels of various paclitaxel formulations continue to warn of high hypersensitivity risk and recommend corticosteroid and H2-antagonist premedication. The authors conclude that the currently available evidence supports implementing oral cetirizine as paclitaxel premedication in clinical practice, offering a safe, effective, and patient-centered option that reduces adverse events and time spent in the hospital.

Subject of Research: Comparing oral cetirizine with intravenous clemastine for preventing paclitaxel hypersensitivity reactions in breast cancer patients

Article Title: Optimizing paclitaxel pretreatment: cetirizine as a safe and patient-centered alternative to clemastine

Article References: Fiebrich-Westra, H. B., Op ’t Hoog, C. J. P., Brohet, R. M., Boerrigter, E., & Smolders, E. J. (2026). Optimizing paclitaxel pretreatment: cetirizine as a safe and patient-centered alternative to clemastine. Drugs & Therapy Perspectives. https://doi.org/10.1007/s40267-026-01265-6

Image Credits: AI Generated

DOI: 10.1007/s40267-026-01265-6

Keywords: paclitaxel, cetirizine, clemastine, hypersensitivity reactions, breast cancer, premedication, antihistamines, chemotherapy, adverse events, supportive care, observational study, sedation