May 2012

Question 1

Drug Interaction Alerts

Answer 1

Up to 90% of alerts now simply overridden
Only one serious interaction prevented for every 2700 alerts

Discontinued drugs cause many alerts but most aren’t serious
Watch for those with lingering effects; amiodarone, fluoxetine, and MAOIs can effects can occur for 2 weeks or more

Be careful when cytochrome P450 inhibitors/inducers are stopped; dosing for other drugs may need to be adjusted

Drug class alerts can be inappropriate if only specific drugs in a class interact 
Not all statins interact with 3A4 inhibitors 
Not all macrolides interact with 3A4 substrates 

Serotonin syndrome comes up often
It is very rare and not likely to occur at all with triptan/SSRI combo
Avoid MAOIs with other serotonergic drugs
Caution with Zyvox plus SSRI/SNRI

QT interval alerts are common
Torsades is rare but life threatening if occurs
High risk patients: women, elderly, heart failure, low heart rate, low serum K or Mg; recommend alternate drug

Biggies
Potassium sparing diuretics with ACEI/ARB
Bactrim with warfarin or potassium boosting meds
Clarithromycin with digoxin or some statins
OCs with enzyme inducers
Interactions with narrow therapeutic index drugs

Question 2

Statins

Answer 2

Statin patients will get fewer LFTs
Patients often get tested when starting, with dose increase and then once or twice a year

Routine monitoring costs $3billion per year and is not helpful: no longer recommended

Any serious liver injury is idiosyncratic and not picked up by routine monitoring
Liver failure is rare if it even happens at all

Only one case of liver failure for every 1 million people on a statin; same as for people not on a statin

New recommendation
LFTs before starting a statin and then only if symptoms (like unexplained nausea, abdominal pain, jaundice

Statins are okay in patients with elevated liver enzymes due to chronic stable liver disease (especially nonalcoholic fatty liver disease- may actually lower liver enzymes by possibly decreasing inflammation in this case)

Avoid statins in acute liver failure or decompensated cirrhosis