[Rich66]

Although my mom has had to go to non contrast CTs, I remember premeds more like:
http://svhrad.com/svhrad2/index.php?...123&Itemid=306

Dex seems more typically used with chemos, not as a scan premed.

This guideline has premed discussion info on page 5, specifics page 8:

http://www.acr.org/SecondaryMainMenu...ullManual.aspx

Premedication Strategies
Oral administration of steroids is preferable to IV
administration, and prednisone and methylprednisolone are equally effective. It is preferred that steroids be given beginning at least 6 hours prior to the injection of contrast media regardless of the route of steroid administration whenever possible. It is unclear if administration for 3 hours or fewer prior to contrast reduces adverse reactions.

Two frequently used regimens are:
1. Prednisone: 50 mg by mouth at 13 hours,
7 hours, and 1 hour before contrast media
injection, plus
Diphenhydramine (Benadryl®): 50 mg intravenously,
intramuscularly, or by mouth 1 hour
before contrast medium [12]
or
2. Methylprednisolone (Medrol®): 32 mg by
mouth 12 hours and 2 hours before contrast
media injection. An anti-histamine (as in
option 1) can also be added to this regimen
injection [34]. If the patient is unable to take
oral medication, 200 mg of hydrocortisone
intravenously may be substituted for oral
prednisone in the Greenberger protocol.

Emergency Premedication
(In Decreasing Order of Desirability)
1. Methylprednisolone sodium succinate (Solu-
Medrol®) 40 mg or hydrocortisone sodium
succinate (Solu-Cortef®) 200 mg intravenously
every 4 hours (q4h) until contrast study
required plus diphenhydramine 50 mg IV 1
hour prior to contrast injection [35].
2. Dexamethasone sodium sulfate (Decadron®)
7.5 mg or betamethasone 6.0 mg intravenously
q4h until contrast study must be done in patent
with known allergy to methylprednisolone, aspirin,
or non-steroidal anti-inflammatory drugs,
especially if asthmatic. Also diphenhydramine
50 mg IV 1 hour prior to contrast injection.
3. Omit steroids entirely and give diphenhydramine
50 mg IV.
Note: IV steroids have not been shown to be
effective when administered less than 4 to 6
hours prior to contrast injection.
Changing the Contrast Agent to be Injected
In patients who have a prior, documented contrast
reaction, the use of a different contrast agent, has
been advocated and may sometimes be protective
[36]. However, a change from one to another lowosmolality agent generally appears to provide little or no benefit [37]. An optional switch to a different agent may be combined with a pre-medication regimen.

A large nonrandomized nonblinded study suggests significantly greater safety of nonionic contrast agents [1]. Similar safety margins have been claimed in other nonrandomized trials [21]; however, no definitive unbiased randomized clinical trials exist that demonstrate significant reduction in severe reactions and fatality [21]. Low-osmolality contrast agents also reduce the non-idiosyncratic physiologic reactions that are not related to allergy. For these reasons there is general agreement that the safety margin for low osmolality contrast agents is better than that for ionic high-osmolality agents