Substrate
The drug being metabolized. It is the passenger on the CYP route.
enzyme acts → drug level changes
Interactive CYP450 study guide
Stop memorizing lists.
See the metabolic traffic.
CYP450 enzymes help metabolize many medications. This learning tool shows how common substrates, inhibitors, and inducers change drug exposure using one visual model, five enzyme stories, and active-recall games.
Terminology note: the standard term is substrate, not producer.
CYP enzymeMETABOLIC ROUTE
SUB
SUB
Inhibitor
slows the route
Inducer
speeds the route
What this is
A practical guide to CYP450 drug interactions.
Cytochrome P450 enzymes are proteins found mainly in the liver and intestine. They help convert many drugs into forms the body can use or eliminate. Another drug, food, herb, or smoking can slow or speed an enzyme, changing the concentration and effect of its substrates.
Learnthe five highest-yield CYP pathways
Predictwhether drug exposure rises or falls
Recallcommon examples with memorable patterns
The one-minute model
Brake. Passenger. Accelerator.
Always identify the substrate first. Then ask what happened to its enzyme.
Inhibitor = brake
Less metabolism usually means more parent drug and more toxicity risk.
enzyme → substrate
Inducer = accelerator
More metabolism usually means less parent drug and possible treatment failure.
enzyme → substrate
EXAM TRAP
Prodrugs flip the usual result. If metabolism activates the drug, an inhibitor can reduce effect. Think codeine and tamoxifen at CYP2D6, and clopidogrel at CYP2C19.
Master mnemonics
Two hooks carry most of the load.
INHIBITORSSLOW
G PACMAN
Grapefruit · Protease inhibitors · Azoles · Cimetidine · Macrolides · Amiodarone · Non-DHP CCBs
2D6 add-on: F-P-B = fluoxetine, paroxetine, bupropion.
INDUCERSFAST
Cars Race Past Pharmacies to St. John’s
Carbamazepine · Rifampin · Phenytoin · Phenobarbital · St. John’s wort
1A2 add-on: smoke signals speed CYP1A2.
The high-yield five
Learn each enzyme as a scene.
Statins, Sedatives, Sildenafil, and Suppressants all travel the 3A highway.
Substrates
- simvastatin / lovastatin
- atorvastatin
- midazolam / triazolam
- quetiapine
- sildenafil / tadalafil
- tacrolimus / cyclosporine
- colchicine
Inhibitors
- clarithromycin
- itraconazole / ketoconazole
- ritonavir / cobicistat
- grapefruit juice
- diltiazem / verapamil
Inducers
- rifampin
- carbamazepine
- phenytoin
- phenobarbital
- St. John’s wort
Clinical pearlA strong inhibitor can sharply raise a sensitive substrate. A strong inducer can make it fail.
Bonus enzymes CYP2B6 and CYP2C8 +
CYP2B6: remember bupropion and efavirenz as substrates. Rifampin and carbamazepine induce it.
CYP2C8: remember repaglinide and pioglitazone as substrates. Gemfibrozil strongly inhibits it, clopidogrel moderately inhibits it, and rifampin induces it.
Memory arcade
Retrieval beats rereading.
Use these short drills until the role and enzyme come to mind without the list.
Is this drug mainly a substrate, inhibitor, or inducer?
clarithromycin
Drug 1 of 8Game 03 · Case quiz
Can you predict the direction?
Do not memorize the pair. Identify the enzyme, the role, and the expected result.
Question 1 of 5
SCORE 0/5
Clarithromycin is added to simvastatin. What is the core concern?
The 10-second check
Substrate first. Enzyme second. Direction third.
1. Name the victim drug→2. Find its CYP route→3. Brake or accelerator?