Drug Interactions

ALCOHOL
- Chronic alcoholism results in enzyme induction.
- Inhibit drug metabolism
- Disulfiram like reaction in the presence of other
drugs
- CNS depression
ALLOPURINOL
- Inhibits drug metabolism enzymes
- Febuxostat – inhib. met. Of azathioprine and
mercaptopurine
ANTACIDS
- Adsorbs drug in GI, dec. absorption.
- Speed gastric emptying delivery to absorption
site quickly.
- MgOH alakalinize urine
ANTIDEPRESSANTS ( TRICYCLIC AND HETEROCYCLIC)
- Inhib. of amine uptake
- Additive in other antimuscarinic drugs
- Metabolism inducible
- Susceptible to inhib of metabolism vi
CYP2D6,CYP3A4 and other CYP450 enz.
ANTIHISTAMINES
- Antimuscarinic
- Sedative
AZOLE ANTIFUNGALS
- Inhibition of CYP3A4, CYP2C9
- GI absorption ph dependent
- Inhib. of P-glycoprotein
BARBITURATES, esp. PHENOBARBITAL
- Induction of hepatic microsomal drug
metabolizing enzymes
- Additive CNS depression
B –BLOCKERS
- Reduce hepatic blood flow
BILE ACID- BINDING RESINS
- Bind with drugs in GI
- Bind in GI drugs that undergo enterohepatic
circulation.
CALCIUM CHANNEL BLOCKERS
- Inhib. Hepatic drug metabolizing enzymes
- Metabolism via CYP3A4
CARBAMAZEPINE
- Induction of hepatic microsomal drug-
metabolizing enzymes
- Susceptible to inhib of metabolism, primarily by
CYP3A4
CIMETIDINE
- May inhibit renal tubular secretion of weak
bases
CISAPRIDE
- Increase in serum can result in ventricular
arrhythmias
COLCHICINE
- Susceptible to inhibition of CYP3A4 metabolism
and P-glycoprotein transport.
CYCLOSPORINE
- Metabolism inducible
- Susceptible to inhib. of metabolism by CYP3A4
DIGITALIS GLYCOSIDES
- Digoxin susceptible to alteration of GI
absorption
- Digitalis toxicity increase by drug induces
electrolyte imbalance
METRONIDAZOLE, CEPHALOSPHORINE
- Inhibition of CYP2CA, CYP3A3/4, CYP3A5-7
DISULFIRAM
- Inhibits aldehyde dehydrogenase
ERYTHROMYCIN
- Inhibits CYP3A4 and P-glycoprotein
ESTROGENS
- Enterohepatic circulation may be interrupted by
alteration in bowel flora
FURANOCOUMARINS
- Inhibitors of CYP3A4
HMG-CoA REDUCTASE INHIBITORS
- Increased risk of additive myopathy risk with
other drugs that can cause myopathy
IRON
- Binds with drugs in GI tract, reducing absorption
LEVODOPA
- Degraded in GUT prior to reaching sites of
absorption
- Agents that alter GI motility may alter degree of
intraluminal degradation
LITHIUM
- Renal lithium excretion sensitive to changes in
sodium balance
MACROLIDES
- Clarithromycin, Erythromycin are known to
inhib. CYP3A4 and P-glycoprotein
- Azithromycin modest inhib of P-glycoprotein
MAOIs
- Inc. Norepinephrine stored in adrenergic
neuron
- Have intrinsic hypoglycemic activity
NSAIDS
- Porstaglandin inhib may result in reduced renal
sodium excretion, reduced renal lithium
excretion
- May increased likelihood of bleeding due to
other drugs that impair hemostasis
ORAL ANTICOAGULANTS
- Highly bound to plasma proteins
- Anticoagulation response altered by drugs that
affect clotting factor synthesis or catabolism
PHENYTOIN
- Induces hepatic microsomal drug metabolism
PIMOZIDE
- May exhibit additive effects with other agents
that prolong QT interval
POTASSIUM SPARING DIURETICS
- Inc. serum potassium concentration
- May alter renal excretion of substances other
than potassium
PROBENICID
- Interference with renal excretion of drugs that
undergoactive tubular secretion, esp weak acids
- Inhibition of glucoronide conjugation of other
drugS
QUINIDINE
- Substrate of CYP3A4
- Inhibits CYP2D6
- Renal excretion susceptible to changes in urine
Ph
QUINOLONE ANTIBIOTICS
- Susceptible to inhibition of GI absorption
RIFAMPICIN
- Inducer of hepatic microsomal drug
metabolizing enzymes
RITONAVIR
- Mixed competitive and irreversible inhibitor of
CYP3A4
SALICYLATES
- Large doses have intrinsic hypoglycemic activity
THEOPHYLLINE
- Susceptible to inhibition of hepatic metabolism
by CYP1A2
DONG QUAI – WARFARIN
GARLIC, GINGKO – Anticoagulants, Antiplatelet agents
GINSENG – Antidepressants
KAVA- Sedative-hypnotics
LIQUORICE ROOT – ALDOSTERONE, Antihypertensive
drugs
MA HUANG, EPHEDRA PREPS. – Sympathomimetics
ST. JOHNS WORT – Oral contraceptives, Cycloserine.
Digoxin, HIV protease inhib. Warfarin
ALCOHOL – Cough syrups, Cold prep, Mouthwashes
ANTIHISTAMINES – Analgesics, Menstrual products,
Sleepaids
ASPIRIN other SALICYLATES – Antidiarrheals,
Cold/Allergy prep.
CAFFEINE – Analgesics, Menstrual prod. Stimulants
LOCAL ANESTHETICS – Antitussive/lozenges,
Dermatologic prep. Hemorrhoidal prod. Toothache,
Cold sore, Teething prod.
SODIUM – Analgesics, Antacids, Cold/cough prep.
Laxatives
SYMPATHOMIMETICS – Analgesics, Asthma prod.
Cold/Cough?Allergy prep. Hemorrhoidal prod.