6mg rapid IV push over 1-2s
If ineffective can try 12mg 2min later
If still ineffective can try another 12mg
Caveat
For patients taking methylxanthines (ie caffeine, theophylline):
Blocks<unk>  binding at receptor sites (competitive antagonist) and can lead to bronchospasm; requires larger dose of<unk> 
Consider using lower dose (1st 3mg, 2nd/3rd 6mg) in patient taking carbamazepine (Tegretol), diazepam (Valium) or dipyridamole (Persantine) OR with a heart transplant.
Traditionally given via stopcock with immediate flush secondary to very short half life. Newer study showing that you may be able to mix with normal saline and give as single push, however further evidence is still needed.
If ineffective can try 12mg 2min later
If still ineffective can try another 12mg
For patients taking methylxanthines (ie caffeine, theophylline):
Blocks<unk>  binding at receptor sites (competitive antagonist) and can lead to bronchospasm; requires larger dose of<unk> 
Consider using lower dose (1st 3mg, 2nd/3rd 6mg) in patient taking carbamazepine (Tegretol), diazepam (Valium) or dipyridamole (Persantine) OR with a heart transplant.
Blocks<unk>  binding at receptor sites (competitive antagonist) and can lead to bronchospasm; requires larger dose of<unk>
Adenosine
Dobutamine
Isoproterenol
Norepinephrine
Epinephrine
Esmolol
Lidocaine
Propafenone