Common Drugs Inducing or Inhibiting Cytochrome P450 Enzymes and the P-Glycoprotein Transporter System

Description

Many adverse drug effects are caused by one drug inhibiting or inducing the metabolism or excretion of a second drug. By recognizing drugs that have these effects many drug interactions can be reduced.

Cytochrome P450 enzymes important in drug metabolism:

(1) CYP1A2

(2) CYP2C9

(3) CYP2C19

(4) CYP2D6

(5) CYP3A4

The P-glycoprotein (P-gp) transport system is important for the excretion of many drugs.

Effect on Target Drug	Inhibitor	Inducer
dose requirement	reduces	increases
toxic effect from accumulation	possible	unlikely
subtherapeutic	unlikely	possible

	Inhibit P450	Induce P450	Inhibit P-gp	Induce P-gp
amiodarone	CYP2D6, CYP3A4		Yes
amprenavir				Yes
barbiturates		CYP3A4
carbamazepine		CYP3A4
carvedilol			Yes
cimetidine	CYP1A2, CYP2C19, CYP2D6
ciprofloxacin	CYP1A2
clarithromycin	CYP3A4		Yes
clotrimazole				Yes
cyclosporine			Yes
efavirenz		CYP3A4
erythromycin	CYP3A4		Yes
fluconazole	CYP2C9, CYP3A4
fluoxetine	CYP2D6
fluvastatin	CYP2C9
fluvoxamine	CYP1A2, CYP2C19
grapefruit juice	CYP3A4
haloperidol	CYP2D6
imatinib	CYP2C9, CYP2D6, CYP3A4
indinavir	CYP3A4
isoniazid	CYP2C19, CYP3A4
itraconazole	CYP3A4		Yes
ketoconazole	CYP3A4		Yes
nefazodone	CYP3A4
nevirapine		CYP3A4
omeprazole		CYP1A2
paroxetine	CYP2D6
phenothiazine				Yes
phenytoin		CYP3A4
quinidine	CYP2D6		Yes
rifampin		CYP2C9, CYP2C19, CYP3A4		Yes
ritonavir	CYP2D6, CYP3A4	CYP3A4	Yes	Yes
St John's wort		CYP3A4		Yes
tamoxifen			Yes
ticlopidine	CYP1A2
tobacco		CYP1A2
troleandomycin	CYP3A4
verapamil			Yes
zafirlukast	CYP2C9

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Description

Specialty

ICD-10