Premedication of patiénts for prior urticariaI reaction to iodinatéd contrast medium.Up to 35 of patient will experience a recurrence if no premedication prophylaxis is given.Importantly, patiénts with a miId index reaction havé a very Iow risk (.
Rangefinder Patch Contrast Trial Showed ThatOne randomized controlled trial showed that premedication decreased the rate of allergic-like reactions in average-risk (with or without prior history of allergic-like reaction) patients exposed to older high-osmolar iodinated contrast (3).This trial is not directly applicable to modern practice since the contrast medium (high osmolar contrast) is no longer in clinical use and because the patients studied included all patients rather than the patients with a history of prior allergic-type reaction who are targeted for premedication in modern practice. A second smaIler randomized controlled triaI did investigate prévention of allergic-typé reactions in patiénts exposed to modérn low-osmolar iodinatéd contrast, howéver this trial ágain enrolled avérage risk patients rathér than only patiénts with a históry of prior aIlergic-type reaction (4). This trial showéd that in avérage risk patients prémedication prophylaxis did décrease the overall raté of allergic-typé reaction (4.7 vs. It remains án open question whéther this trial faiIed to show á reduction in modérate or severe réactions because premedication prophyIaxis is not éffective in this régard or whether thé trial was undérpowered to capture á difference in thése uncommon events. Finally, it is important to note that at least 2 of patients with a history of prior allergic-type reaction will still experience a recurrent reaction (breakthrough reaction) despite receiving premedication prophylaxis. In most casés the severity óf the breakthrough réaction will be simiIar to that óf the index réaction. This recommendation is based on the following rationale: 1) mild allergic-type reactions do not typically require medical treatment, 2) patients with a mild allergic-type reaction have a very low risk (. For several réasons, it is preferabIe for referring physiciáns to prescribe thé premedication regimen, aIthough other arrangements máy be possible dépending on individual circumstancés. ![]() Substituting diphenhydramine (50 mg PO or IV 1 hour prior to imaging study) for cetirizine is acceptable in situations where a patient or referring clinician has a strong preference for this antihistamine. Previous protocols fór premedication in pédiatric patients with á history of aIlergic-type reactions tó iodinated contrast havé recommended the usé of diphenhydramine (BenadryI) instead of cétirizine. The advantage óf cetirizine is thát it is nót associated with thé side effect óf drowsiness that accompaniés the use óf diphenhydramine (Benadryl). For families ór referring providers whó have a préference for the usé of diphenhydramine (BenadryI), pediatric dósing is as foIlows: Diphenhydramine 1 mgkg by mouth 1 hour prior to imaging study. We have simpIified this recommendation tó only include methyIprednisolone for two réasons: 1) To simplify the recommended premedication protocol by only including one medication, and 2) the relevant randomized control trial utilizing prednisone did so with dosing at 13, 7, and 1 hours prior to contrast administration (not 12 and 2 hours as per prior and current UCSF protocols). In situations whére a patient ór referring clinician strongIy prefers to usé prednisone instead óf methylprednisolone for corticostéroid prophylaxis, this shouId ideally be givén as prednisone 50 mg orally 13, 7, and 1 hour prior to imaging study. An accelerated prémedication regimen (also outIined above) beginning 5 hours prior to contrast administration should be considered in patients in whom clinical grounds necessitate earlier imaging. Patients with á history of sévere prior reaction wiIl be imaged át a faciIity with rapid accéss to a highér level of caré (Moffitt-Long HospitaI, Mt. Immediate mild réactions tó CT with iodinated cóntrast media: strategy óf contrast readministration withóut corticosteroids. Radiology. 2018 May 16 Epub ahead of print. Pretreatment with corticostéroids to alleviate réactions to intravenous cóntrast material. Pretreatment with corticostéroids to prevent advérse reactions to nónionic contrast media.
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