What is the interaction between oral prednisone and Zyrtec (cetirizine)?

From the Guidelines

Oral prednisone and Zyrtec (cetirizine) should not be discontinued together without considering the risks of drug withdrawal and the potential for suppression of late-phase responses in the context of an oral food challenge (OFC) 1. When managing patients on these medications, it's crucial to weigh the benefits of stopping them against the potential risks, especially for those on chronic steroid therapy.

• For oral prednisone, the guideline suggests stopping it 3 days to 2 weeks before an OFC, considering the potential for suppression of late-phase responses and the risk of exacerbating the condition being treated 1.
• For Zyrtec (cetirizine), the recommendation is to stop it 5-7 days before an OFC to avoid interference with the interpretation of the challenge results 1. In clinical practice, the decision to stop these medications should be made on a case-by-case basis, considering the individual patient's condition, the reason for the OFC, and the potential risks and benefits of stopping or continuing the medications.
• Patients should be closely monitored during the OFC, with vital signs measured and the patient re-examined before each dose is administered, to promptly identify and treat any allergic reactions that may occur 1. It's also important to note that certain medications, such as aspirin and other nonsteroidal anti-inflammatory agents, should be avoided due to their potential to enhance or induce allergic reactions and interfere with OFC outcome interpretation 1.

From the Research

Oral Predisone and Zyrtec

• The combination of oral predisone and Zyrtec (cetirizine) is not directly addressed in the provided studies, but we can gather information about the individual components and their interactions with other substances.
• Predisone is a steroid that has potent anti-inflammatory and immune-modulating properties, as discussed in 2.
• Zyrtec, on the other hand, is an antihistamine that can be used to treat allergic reactions, and its effects on pulmonary function have been studied in patients with mild-to-moderate asthma, as shown in 3.

Steroid Use and Side Effects

• The use of steroids like predisone can have various side effects, which can occur at a wide range of doses and vary depending on the route of administration, as mentioned in 2.
• In some cases, steroids can exacerbate preexisting conditions or present new medical conditions, highlighting the need for practitioners to be aware of the clinical implications of prescribing these agents.

Combination Therapies

• The study in 4 investigated the combination of prednisone, azathioprine, and N-acetylcysteine for pulmonary fibrosis, but found increased risks of death and hospitalization, which led to the termination of the combination-therapy group.
• In contrast, the study in 5 found that the addition of prednisone to levocetirizine did not improve the symptomatic and clinical response of acute urticaria, suggesting that the combination of a steroid with an antihistamine may not always be beneficial.

Antihistamine and Bronchodilatory Effects

• Cetirizine, the active ingredient in Zyrtec, has been shown to have a significant bronchodilatory effect in patients with mild-to-moderate asthma, as demonstrated in 3.
• This study also found that cetirizine did not potentiate or inhibit the bronchodilatory action of albuterol, but rather had an additive effect, suggesting that the combination of an antihistamine with a bronchodilator may be beneficial in certain cases.