Common Drug Stems
These stems are not informal study tricks. They are assigned through a formal nomenclature system: the USAN Council (cosponsored by the American Medical Association, the U.S. Pharmacopeia, and the American Pharmacists Association) maintains the approved stems for drug names marketed in the United States, and the World Health Organization coordinates the matching international list through its INN Programme (AMA USAN; WHO INN Stem Book). Each stem carries hyphens at one or both ends to show where it falls in the generic name (beginning, middle, or end).
| STEM | DEFINITION | EXAMPLES |
|---|---|---|
| -ac | NSAID (acetic acid derivatives) | bromfen ac, dexpemedol ac |
| -adol- | mixed opiate receptor agonists/antagonists | levonantr adol, spir adol ine, taz adol ene |
| -afil | Inhibitor of PDE5 with vasodilator action | silden afil (viagra), tadal afil |
| -alol | Combined alpha and beta blockers | labet alol, medrox alol |
| -andr- | Androgens | n andr olone |
| -anib | Angiogenesis inhibitors (inhibits growth of new blood vessels) | Pazop anib, Vandet anib |
| -anserin | Serotonin 5-HT(sub)2 receptor antagonists | alt anserin, trop anserin |
| -arabine | Antineoplastics (arabinofuranosyl derivatives) | flud arabine |
| -ase | Enzymes | alglucer ase, dorn ase alfa |
| -atadine | Tricyclic antiasthmatics | olop atadine, lor atadine |
| -axine | Antianxiety, antidepressant | venlaf axine |
| -azenil | Benzodiazepine receptor agonists/antagonists | bret azenil, flum azenil |
| -azepam | Antianxiety agents (diazepam type) | lor azepam, di azepam |
| -azepide | Cholecystokinin receptor antagonists | dev azepide |
| -azocine | Narcotic antagonists/agonists | quad azocine, ket azocine |
| -azoline | Antihistamines /local vasoconstrictors | ant azoline |
| -azosin | Antihypertensives (prazosin type) | dox azosin |
| -bactam | Beta-lactamase inhibitors | sul bactam |
| -bamate | Tranquilizers/antiepileptics | mepro bamate, fel bamate |
| -barb- | Barbituric acid derivatives | pheno barb ital, seco barb ital |
| -bersat | Anticonvulsants ; antimigraine | cara bersat ; tidem bersat |
| -bufen | NSAID (fenbufen derivatives) | indo bufen |
| -butan | Antiseptics | dapa butan, lop butan |
| -butazone | Anti-inflammatory analgesics (phenylbutazone type) | mofe butazone |
| -caine | Local anesthetics | lido caine, dibu caine |
| -carbef | Antibiotics (carbacephem derivatives) | lora carbef |
| -cillin | Penicillins | ampi cillin, peni cillin, oxa cillin |
| -cog | blood coagulation factors | epta cog alfa, nona cog alfa, octo cog alfa |
| -conazole | Antifungals (miconazole type) | flu conazole, oxi conazole |
| -cort- | Cortisone derivatives | hydro cort isone |
| -curium | Neuromuscular blocking agents | atra curium |
| -cycline | Antibiotics (tetracycline type) | mino cycline, tetra cycline |
| -dralazine | Antihypertensives (hydrazine-phthalazines) | hy dralazine |
| -dronate | Calcium metabolism regulators | eti dronate, tilu dronate |
| -ectin | Antiparasitics (ivermectin type) | doram ectin, moxid ectin |
| -erg- | Ergot alkaloid derivatives | p erg olide |
| -etanide | Diuretics | bum etanide |
| -fenamic acid | Anti-inflammatory agents | me fenamic acid, flu fenamic acid |
| -fentanil | Narcotic analgesics | al fentanil, mir fentanil |
| -fibrate | Antihyperlipidemics | beza fibrate |
| -flurane | Inhalation anesthetics | en flurane, iso flurane |
| -gest- | Progestins | me gest rol |
| -giline | MAO-inhibitors, type B | sele giline |
| -gillin | Antibiotics (aspergillus strains) | mito gillin |
| -gliptin | Antihyperglycemics | vilda gliptin |
| -glitazar | Antihyperglycemics, PPRA agonists | far glitazar |
| -glizatone | Antihyperglycemics, PPST agonists | ci glitazone, rosi glitazone |
| -grel- | Platelet aggregation inhibitor | clopido grel, tica grel or |
| -imex | Immunostimulants | forfen imex, roquin imex |
| -imus | Immunosuppresives | tacrol imus, napir imus, gusper imus |
| -irudin | Anticoagulants | des irudin |
| -leukin | Interleukin -2 derivatives | tece leukin, aldes leukin |
| -lukast | Leukotriene antagonists | monte lukast, zafir lukast |
| -mab | Monoclonal antibodies | capro mab, daclizu mab, detumo mab |
| -mantadine | Antivirals | ri mantadine |
| -milast | Antiasthmatics/antiallergics; type IV phosphodiesterase inhibitors | picla milast |
| -monam | Monobactam antibiotics | gloxi monam |
| -mustine | Antineoplastics | carm ustine |
| -mycin | Antibiotics (streptomyces strains) | linco mycin |
| -olol | Beta-blockers (propranolol type) | tim olol, aten olol |
| -olone | Steroids (no prednisone derivatives) | minax olone |
| -orphan | Narcotic antagonists/agonists | methr ophan, dextr orphan |
| -oxacin | Antibiotics (quinolone derivatives) | difl oxacin, ciprofl oxacin |
| -oxetine | Antidepressants | dul oxetine, reb oxetine |
| -pamide | Diuretics (sulfamoylbenzoic acid derivatives) | adi pamide |
| -pamil | Coronary vasodilators | tia pamil |
| -parin | Heparin derivatives | he parin, tinza parin, dalte parin |
| -peridol | Antipsychotics (haloperidol type) | halo peridol |
| -peridone | Antispsychotics (risperidone type) | ris peridone, ilo peridone |
| -pidem | Hypnotics /sedatives (zolpidem) | zol pidem, al pidem |
| -piridine | Cognition enhancers | lino piridine, besi piridine |
| -poetin | Erythropoietins | e poetin alfa, e poetin beta |
| -pramine | Antidepressants (imipramine type) | lofe pramine |
| -prazole | Proton-pump inhibitor | ome prazole, lanso prazole |
| -pred- | Prednisone derivatives | pred nicarbate, clo pred nol |
| -pril | Antihypertensives (ACE inhibitors) | capto pril, temoca pril, spira pril |
| -profen | Anti-inflammatory/analgesic agents (ibuprofen type) | flurbi profen |
| -prost- | Prostaglandin analogue | latano prost, uno prost one |
| -rubicin | Antineoplastic antibiotics (daunorubicin type) | epi rubicin, ida rubicin |
| -sartan | Angiotensin II receptor antagonists | lo sartan, epro sartan |
| -statin | Renal dehydropeptidase inhibitor pepsin inhibitor | cila statin, pep statin |
| -ster- | Steroids (androgens, anabolics) | testo ster one |
| -sulfa | Antibiotics (sulfonamide derivatives) | sulfa salazine |
| -tegrast | Antiasthmatics/antiallergics; integrin antagonists | vala tegrast |
| -terol | Bronchodilators (phenethylamine derivatives) | albu terol |
| -thiazide | Diuretics (thiazide derivatives) | chloro thiazide |
| -tide | peptides and glycopeptides | Nesiri tide, Octreo tide |
| -tocin | Oxytocin derivatives | oxy tocin, pi tocin |
| -trexate | Antimetabolites (folic acid derivatives) | metho trexate |
| -triptyline | Antidepressants | ami triptyline |
| -trodast | Antiasthmatics/antiallergics; thromboxane A2 receptor antagonists | sera trodast |
| -uracil | Uracil derivatives used as thyroid antagonists and as antineoplastics | fluoro uracil |
| -vastatin | Antihyperlipidemics (HMG-CoA inhibitors) | lo vastatin, sim vastatin |
| -zolast | Antiasthmatics/antiallergics; benzoxazole derivatives | ecla zolast, onta zolast |
| -zumab | humanized antibodies | natali zumab, bevaci zumab |
| bol-, -bol- | Anabolic steroids | bol andiol, mi bol erone |
| cef- | Cephalosporins (first-gen) | cef azolin |
| estr- | Estrogens | estr one |
| vir-, -vir- or -vir | Antiviral substances (undefined group) | vir oxime, en vir odyne, ganciclo vir |
Frequently Asked Questions
What is a drug stem? A stem is a shared word element built into the generic (nonproprietary) name of every drug in a related group. Drugs that share pharmacology usually share a stem, so the stem tells you the class on sight. For example, every "-pril" is an ACE inhibitor and every "-olol" is a beta-blocker.
Who decides what the stems are? The USAN Council assigns United States Adopted Names and their stems; it is cosponsored by the American Medical Association, the U.S. Pharmacopeia, and the American Pharmacists Association. The World Health Organization runs the parallel international system through its International Nonproprietary Names (INN) Programme. The two bodies coordinate so a given stem means the same thing worldwide.
Are stems always at the end of the name? Usually, but not always. Most stems are suffixes (-statin, -sartan, -cillin), a few are prefixes (cef- for cephalosporins, estr- for estrogens), and some sit in the middle (-barb-, -cort-). The hyphens in a published stem list show you where the stem falls.
Why do stems matter for patient safety? A single drug can carry many brand names, and one branded product can contain more than one drug, so brand names are an unreliable way to know what you are giving. The generic stem keeps communication precise and cuts prescribing and administration errors, which is the whole reason the nomenclature system exists.
Can I rely on a stem to predict every side effect? No. A stem places a drug in its class, which gets you the general mechanism and the major class effects, but individual agents still differ in potency, route, interactions, and specific warnings. Use the stem to orient yourself, then confirm the specifics for the actual drug.
Does knowing stems help on the NCLEX? Yes. Pharmacology questions often name a drug you have not memorized. Recognizing the stem lets you place it in a class, recall the class actions and nursing priorities, and reason your way to the answer instead of guessing.