Page 1184 - Basic _ Clinical Pharmacology ( PDFDrive )

1170 SECTION X Special Topics

TABLE 66–1 Important drug interactions.

Drug or Properties Promoting
Drug Group Drug Interaction Clinically Documented Interactions
Phenytoin Drugs that inhibit phenytoin metabolism:
(cont.)
Amiodarone: [P] Increased serum phenytoin concentration; possible reduction in
serum amiodarone concentration.
Capecitabine: [NE] Increased phenytoin plasma concentrations.
Chloramphenicol: [P] Increased phenytoin plasma concentrations.
Felbamate: [P] Increased phenytoin plasma concentrations.
Fluorouracil: [NE] Increased phenytoin plasma concentrations.
Fluvoxamine: [NP] Increased phenytoin plasma concentrations.
Isoniazid: [NP] Increased serum phenytoin; problem primarily with slow acetylators of
isoniazid.
Metronidazole: [NP] Increased phenytoin plasma concentrations.
Sulfamethoxazole: [P] Increased phenytoin plasma concentrations.
Ticlopidine: [NP] Increased phenytoin plasma concentrations.
See also Azole antifungals; Cimetidine; Disulfiram.
Drugs that enhance phenytoin metabolism:
Bosentan: [P] Decreased phenytoin plasma concentrations.
Carbamazepine: [P] Decreased phenytoin plasma concentrations.
Rifampin: [P] Decreased phenytoin plasma concentrations.
St. John’s wort: [P] Decreased phenytoin plasma concentrations.
See also Barbiturates.
Pimozide Susceptible to CYP3A4 inhibitors; Antivirals: [P] Amprenavir, atazanavir, boceprevir, darunavir, delavirdine, fosamprenavir,
may exhibit additive effects with indinavir, nelfinavir, ritonavir, saquinavir, simeprevir, and telaprevir inhibit the
other agents that prolong QT c metabolism of pimozide.
interval.
Boceprevir: [P] Decreased metabolism of pimozide.
Cobicistat: [P] Decreased metabolism of pimozide.
Conivaptan: [P] Decreased metabolism of pimozide.
Kinase inhibitors: [P] Decreased metabolism of pimozide with ceritinib, dasatinib,
imatinib, idelalisib, and lapatinib.
Nefazodone: [NP] Decreased pimozide metabolism.
See also Azole antifungals; Cyclosporine; Macrolides.
Potassium- Additive effects with other agents ACE inhibitors (ACEIs): [NP] Additive hyperkalemic effect.
sparing diuret- increasing serum potassium con-
ics (amiloride, centration. Eplerenone is a substrate Angiotensin II receptor blockers (ARBs): [NP] Additive hyperkalemic effect.
eplerenone, for CYP3A4 and is susceptible to Antivirals: [P] Amprenavir, atazanavir, boceprevir, darunavir, delavirdine,
spironolactone, inhibition and induction. May fosamprenavir, indinavir, nelfinavir, ritonavir, saquinavir, simeprevir, and telaprevir
triamterene) alter renal excretion of substances inhibit the metabolism of eplerenone.
other than potassium (eg, digoxin,
hydrogen ions). Boceprevir: [P] Decreased metabolism of eplerenone.
Cobicistat: [P] Decreased metabolism of eplerenone.
Conivaptan: [P] Decreased metabolism of eplerenone.
E, Expected; HP, Highly predictable. Interaction occurs in almost all patients receiving the interacting combination; P, Predictable. Interaction occurs in most patients receiving the
combination; NP, Not predictable. Interaction occurs only in some patients receiving the combination; NE, Not established. Insufficient data available on which to base estimate
of predictability.
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