Page 1186 - Basic _ Clinical Pharmacology ( PDFDrive )

1172 SECTION X Special Topics

TABLE 66–1 Important drug interactions.

Drug or Properties Promoting
Drug Group Drug Interaction Clinically Documented Interactions
Quinolone Tizanidine: [P] Ciprofloxacin, enoxacin, and, to a lesser extent, norfloxacin inhibit
antibiotics tizanidine metabolism.
(cont.)
Zolmitriptan: [P] Ciprofloxacin, enoxacin, and, to a lesser extent, norfloxacin inhibit
zolmitriptan metabolism.
See also Acid-reducing agents; Anticoagulants, oral; Iron.
Rifampin Inducer (strong) of hepatic Corticosteroids: [P] Increased corticosteroid hepatic metabolism; reduced
microsomal drug-metabolizing corticosteroid effect.
enzymes and P-glycoprotein.
Mexiletine: [NE] Increased mexiletine metabolism; reduced mexiletine effect.
Sulfonylurea hypoglycemics: [P] Increased hepatic metabolism of tolbutamide and
probably other sulfonylureas metabolized by the liver (including chlorpropamide).
Theophylline: [P] Increased theophylline metabolism.
See also Anticoagulants, oral; Antidepressants, tricyclic and heterocyclic; Azole
antifungals; Beta-adrenoceptor blockers; Calcium channel blockers; Cyclosporine;
Digitalis glycosides; Estrogens; HMG-CoA reductase inhibitors; Opioid analgesics;
Phenytoin; Quinidine.
Salicylates Interference with renal excretion of Carbonic anhydrase inhibitors: [NE] Increased acetazolamide serum concentrations;
drugs that undergo active tubular increase salicylate toxicity due to decreased blood pH.
secretion. Salicylate renal excretion
dependent on urinary pH when Corticosteroids: [P] Increased salicylate elimination; possible additive toxic effect on
large doses of salicylate used. gastric mucosa.
Aspirin (but not other salicylates) Heparin: [NP] Increased bleeding tendency with aspirin, but probably not with other
interferes with platelet function. salicylates.
Large doses of salicylates have
intrinsic hypoglycemic activity. Methotrexate: [P] Decreased renal methotrexate clearance; increases methotrexate
toxicity (primarily at anticancer doses).
Selective serotonin reuptake inhibitors (SSRIs): [P] Increased risk of bleeding due to
platelet inhibition.
Sulfinpyrazone: [HP] Decreased uricosuric effect of sulfinpyrazone (interaction unlikely
with less than 1.5 g of salicylate daily).
See also Acid-reducing agents; Anticoagulants, oral; Probenecid.
Selective SSRIs can lead to excessive serotonin Codeine: [HP] Reduced analgesic effect due to inhibition of codeine metabolism to
serotonin response when administered with morphine by fluoxetine and paroxetine.
reuptake other serotonergic drugs (eg,
inhibitors MAOIs). Some SSRIs inhibit various Theophylline: [P] Decreased metabolism of theophylline by fluvoxamine-induced
(SSRIs) cytochrome P450s including inhibition of CYP1A2.
CYP2D6, CYP1A2, CYP3A4, and See also Anticoagulants, oral; Antidepressants, tricyclic and heterocyclic;
CYP2C19. β-Adrenoceptor blockers; Carbamazepine; Cisapride; Colchicine; Cyclosporine;
HMG-CoA reductase inhibitors; Monoamine oxidase inhibitors; Nonsteroidal
anti-inflammatory drugs; Phenytoin; Pimozide; Salicylates.
Theophylline Susceptible to induction and Beta-adrenoceptor blockers: [NP] Decreased theophylline bronchodilation especially
inhibition of hepatic metabolism with noncardioselective β blockers.
by CYP1A2 and CYP3A4.
Smoking: [HP] Increased theophylline metabolism.
Tacrine: [NP] Decreased theophylline metabolism.
Ticlopidine: [NP] Decreased theophylline metabolism.
Zileuton: [NP] Decreased theophylline metabolism.
See also Barbiturates; Calcium channel blockers; Carbamazepine; Cimetidine; Lithium;
Macrolides; Phenytoin; Quinolones; Rifampin; Selective serotonin reuptake inhibitors.
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.