From the Guidelines
Pre-medications for MRI should be tailored to the individual patient's needs, with a focus on anxiolytics and sedatives for claustrophobic patients, and premedication regimens for patients with allergies to gadolinium-based contrast agents. The most recent and highest quality study 1 emphasizes the importance of prescreening patients for potentially relevant MRI contraindications using a standardized checklist. For patients with mild anxiety, oral benzodiazepines like diazepam (5-10mg) or lorazepam (1-2mg) can be administered 30-60 minutes before the scan. For moderate to severe claustrophobia, midazolam (1-2mg IV) may be used immediately before the procedure, as suggested by 1. Patients with severe claustrophobia or children who cannot remain still might require procedural sedation with propofol under anesthesia supervision. For patients with allergies to gadolinium-based contrast agents, a premedication regimen of prednisone (50mg orally at 13,7, and 1 hour before the procedure), diphenhydramine (50mg orally 1 hour before), and famotidine (20mg orally 1 hour before) is recommended, although the certainty of evidence around supplemental therapies in anaphylaxis management is very low, as noted in 1. These medications work by reducing anxiety, preventing allergic reactions through antihistamine effects, and stabilizing mast cells to prevent degranulation. Some key points to consider when administering pre-medications for MRI include:
- Informing the MRI team about claustrophobia concerns beforehand to arrange appropriate medications and scheduling accommodations
- Arranging transportation home for patients who will be sedated, as driving afterward is unsafe
- Selecting the lowest dose of drug with the highest therapeutic index for the procedure, as suggested by 1
- Considering the potential for biphasic reactions in patients with anaphylaxis, as discussed in 1
From the Research
Pre-Medications for MRI
- The use of anxiolytics in adult outpatient MRI centers has been evaluated, and it was found that many outpatients may be scanned before the peak effect of anxiolytics prescribed 2.
- A standard sedation protocol in MRI centers is associated with a more appropriate drug choice, as well as optimized monitoring and post-procedure care 2.
- Lorazepam was the most commonly used anxiolytic, but facilities with standard sedation protocols were more likely to use midazolam 2.
Benzodiazepines for Claustrophobia
- The use of low-dose oral benzodiazepines has been shown to increase the odds of successfully completing an MRI brain examination in severely claustrophobic patients 3.
- Wide-bore magnets were also found to be effective in assisting mild, moderately, and severely claustrophobic patients in completing an MRI brain exam 3.
Alternative Interventions
- Simple interventions such as video demonstrations or telephone conversations with a radiographer can significantly reduce pre-MRI anxiety 4.
- Other interventions such as cognitive-behavioral strategies, prone positioning, information, fragrance administration, and team training have also been shown to have a positive impact on reducing anxiety and claustrophobia in MRI patients 5, 6.
- Audiovisual systems and guided imagery have also been found to be effective in reducing anxiety and the need for sedation in MRI patients 5.