Look-Alike Sound-Alike (LASA) Drug Pairs

Look-Alike Sound-Alike (LASA) Drug Pairs

Look-alike and sound-alike (LASA) medications are drugs with names that can be easily confused with each other, leading to dispensing errors. The FDA and ISMP use tall man lettering (capitalizing different portions of drug names) to help differentiate these medications. Pharmacy technicians must be especially vigilant when selecting medications from shelves and entering data into pharmacy systems.

High-Priority LASA Pairs with Tall Man Lettering

Drug Name	Confused With	Tall Man Lettering
hydroxyzine	hydralazine	hydrOXYzine vs. hydrALAZINE
prednisolone	prednisone	prednisoLONE vs. predniSONE
methylprednisolone	medroxyprogesterone	methylPREDNISolone vs. medroxyPROGESTERone
chlorpromazine	chlorpropamide	chlorproMAZINE vs. chlorproPAMIDE
glipizide	glyburide	glipiZIDE vs. glyBURIDE
vincristine	vinblastine	vinCRIStine vs. vinBLAStine
clonidine	clonazepam	cloNIDine vs. cloNAZEPam
clonidine	klonopin (clonazepam brand)	cloNIDine vs. KlonoPIN
bupropion	buspirone	buPROPion vs. busPIRone
daunorubicin	doxorubicin	DAUNOrubicin vs. DOXOrubicin
sulfadiazine	sulfasalazine	sulfADIAZINE vs. sulfaSALAZINE
cyclosporine	cycloserine	cycloSPORINE vs. cycloSERINE
dopamine	dobutamine	DOPamine vs. DOBUTamine
epinephrine	norepinephrine	EPINEPHrine vs. norEPINEPHrine
risperidone	ropinirole	risperiDONE vs. rOPINIRole
acetazolamide	acetohexamide	acetaZOLAMIDE vs. acetoHEXAMIDE
cefazolin	ceftriaxone	(Check NDC and vial label carefully)
olanzapine	quetiapine	OLANZapine vs. QUEtiapine

Brand Name LASA Pairs

Brand Name	Confused With	Generic (A)	Generic (B)
Celebrex	Celexa	celecoxib	citalopram
Zyrtec	Zantac / Zyprexa	cetirizine	ranitidine / olanzapine
Lamictal	Lamisil	lamotrigine	terbinafine
Adderall	Inderal	amphetamine/dextroamphetamine	propranolol
Januvia	Janumet	sitagliptin	sitagliptin/metformin
Paxil	Taxol	paroxetine	paclitaxel
Prilosec	Prozac	omeprazole	fluoxetine
Topamax	Toprol-XL	topiramate	metoprolol succinate
Xanax	Zantac	alprazolam	ranitidine
Humalog	Humulin	insulin lispro	regular human insulin / NPH
NovoLog	Novolin	insulin aspart	regular human insulin / NPH

Strategies to Prevent LASA Errors

• Tall man lettering: Use and recognize tall man letters to differentiate confusing drug names.
• Barcode scanning: Scan the barcode at the point of dispensing to verify the correct product.
• Shelf separation: Store LASA drugs in different locations rather than next to each other.
• Label alerts: Use auxiliary labels, shelf talkers, or computer alerts flagging LASA pairs.
• Read the label three times: When pulling medication from the shelf, when preparing, and when returning to the shelf.
• Verify NDC: Confirm the NDC number matches the prescription when pulling stock.
• Indication check: If the indication does not match the drug pulled, investigate before dispensing.
• Two identifiers: Check both drug name and strength/dosage form.

Exam Tips

• The ISMP maintains an official list of confused drug names - review it before the exam.
• Tall man lettering questions frequently appear on the exam.
• Know which drug in each pair is which - for example, hydrOXYzine is an antihistamine used for anxiety and itching, while hydrALAZINE is an antihypertensive.
• Insulin products (Humalog vs. Humulin, NovoLog vs. Novolin) are among the most commonly confused in practice.
• The pharmacist's final check is the last line of defense, but technicians should catch errors before that point.