Effects of Drugs and Other Substances on Quinine Pharmacokinetics
Drugs and other substances that alter the absorption, distribution, metabolism,
and excretion of quinine may increase or decrease quinine concentrations (see
CLINICAL PHARMACOLOGY).
Antacids: Antacids containing aluminum and/or magnesium may delay
or decrease absorption of quinine. Concomitant administration of these antacids
with Qualaquin should be avoided.
Cholestyramine: In 8 healthy volunteers who received quinine
sulfate 600 mg with or without 8 grams of cholestyramine resin, no significant
difference in quinine pharmacokinetic parameters was seen.
Cigarette Smoking (CYP1A2 Inducer): In healthy male heavy smokers,
the mean quinine AUC following a single 600-mg dose was 44% lower, the mean
Cmax was 18% lower, and the elimination half-life was shorter (7.5 hours versus
12 hours) than in their non-smoking counterparts. However, in malaria patients
who received the full 7-day course of quinine therapy, cigarette smoking produced
only a 25% decrease in median quinine AUC and a 16.5% decrease in median Cmax,
suggesting that the already reduced clearance of quinine in acute malaria could
have diminished the metabolic induction effect of smoking. Because smoking did
not appear to influence the therapeutic outcome in malaria patients, it is not
necessary to increase the dose of quinine in the treatment of acute malaria
in heavy cigarette smokers.
Cimetidine, ranitidine (nonspecific CYP450 inhibitors): In healthy
volunteers who were given a single oral 600 mg dose of quinine sulfate after
pretreatment with cimetidine (200 mg three times daily and 400 mg at bedtime
for 7 days) or ranitidine (150 mg twice daily for 7 days), the apparent oral
clearance of quinine decreased and the mean elimination half-life increased
significantly when given with cimetidine but not with ranitidine. Compared to
untreated controls, the mean AUC of quinine increased by only 20% with ranitidine
and by 42% with cimetidine (p < 0.05) without a significant change in mean
quinine Cmax. When quinine is to be given concomitantly with a histamine H2-receptor
blocker, the use of ranitidine is preferred over cimetidine. Although cimetidine
may be used concomitantly with Qualaquin, patients should be monitored closely
for adverse events associated with quinine.
Erythromycin (CYP3A4 inhibitor): Erythromycin was shown to inhibit
the metabolism of quinine in vitro using human liver microsomes. Therefore,
concomitant administration of erythromycin with Qualaquin is likely to increase
plasma quinine concentrations, and should be avoided (See WARNINGS).
Grapefruit juice (CYP3A4 inhibitor): In a pharmacokinetic study
involving 10 healthy volunteers, the administration of a single 600 mg dose
of quinine sulfate with grapefruit juice (full-strength or half-strength) did
not significantly alter the pharmacokinetic parameters of quinine. Qualaquin
may be taken with grapefruit juice.
Histamine H2-receptor blockers (cimetidine, ranitidine):
In healthy volunteers who were given a single oral 600 mg dose of quinine sulfate
after pretreatment with cimetidine (200 mg three times daily and 400 mg at bedtime
for 7 days) or ranitidine (150 mg twice daily for 7 days), the apparent oral
clearance of quinine decreased and the mean elimination half-life increased
significantly when given with cimetidine but not with ranitidine. Compared to
untreated controls, the mean AUC of quinine increased by only 20% with ranitidine
and by 42% with cimetidine (p < 0.05) without a significant change in mean
quinine Cmax. When quinine is to be given concomitantly with a histamine H2-receptor
blocker, the use of ranitidine is preferred over cimetidine. Although cimetidine
may be used concomitantly with Qualaquin, patients should be monitored closely
for adverse events associated with quinine.
Isoniazid: Isoniazid 300 mg/day pretreatment for 1 week did not
significantly alter the pharmacokinetic parameters of quinine. Adjustment of
Qualaquin dosage is not necessary when isoniazid is given concomitantly.
Ketoconazole (CYP3A4 inhibitor): In a crossover study, healthy
subjects (N=9) who received a single oral dose of quinine hydrochloride (500
mg) concomitantly with ketoconazole (100 mg twice daily for 3 days) had a mean
quinine AUC that was higher by 45% and a mean oral clearance of quinine that
was 31% lower than after receiving quinine alone. Although no change in the
Qualaquin dosage regimen is necessary with concomitant ketoconazole, patients
should be monitored closely for adverse reactions associated with quinine.
Oral contraceptives (estrogen, progestin): In 7 healthy females
who were using single-ingredient progestin or combination estrogen-containing
oral contraceptives, the pharmacokinetic parameters of a single 600 mg dose
of quinine sulfate were not altered in comparison to those observed in 7 age-matched
female control subjects not using oral contraceptives.
Rifampin (CYP3A4 inducer): In patients with uncomplicated P.
falciparum malaria who received quinine sulfate 10 mg/kg concomitantly with
rifampin 15 mg/kg/day for 7 days (N=29), the median AUC of quinine between days
3 and 7 of therapy was 75% lower as compared to those who received quinine monotherapy.
In healthy volunteers (N=9) who received a single oral 600 mg dose of quinine
sulfate after 2 weeks of pretreatment with rifampin 600 mg/day, the mean quinine
AUC and Cmax decreased by 85% and 55%, respectively. Therefore the concomitant
administration of rifampin with Qualaquin should be avoided (See WARNINGS).
Tetracycline: In 8 patients with acute uncomplicated P. falciparum
malaria who were treated with oral quinine sulfate (600 mg every 8 hours for
7 days) in combination with oral tetracycline (250 mg every 6 hours for 7 days),
the mean plasma quinine concentrations were about two-fold higher than in 8
patients who received quinine monotherapy. Although tetracycline may be concomitantly
administered with Qualaquin, patients should be monitored closely for adverse
reactions associated with quinine sulfate.
Troleandomycin (CYP3A4 inhibitor): In a crossover study (N=10),
healthy subjects who received a single oral 600 mg dose of quinine sulfate with
the macrolide antibiotic, troleandomycin (500 mg every 8 hours) exhibited a
87% higher mean quinine AUC, a 45% lower mean oral clearance of quinine, and
a 81% lower formation clearance of the main metabolite, 3-hydroxyquinine, than
when quinine was given alone. Therefore, concomitant administration of troleandomycin
with Qualaquin should be avoided (See WARNINGS).
Urinary alkalizers (acetazolamide, sodium bicarbonate): Urinary
alkalinizing agents may increase plasma quinine concentrations.
Effect of Quinine on the Pharmacokinetics of Other Drugs
Results of in vivo drug interaction studies suggest that quinine has
the potential to inhibit the metabolism of drugs that are substrates of CYP3A4
and CYP2D6, as well as, inhibit the biliary excretion of drugs like digoxin.
In an in vitro induction study using human hepatocytes, quinine (5 to
30 µM) increased the metabolic activities of CYP1A2 and CYP3A4. Quinine did
not significantly induce the activities of CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19,
CYP2D6, and CYP2E1.
Anticonvulsants (carbamazepine, phenobarbital, and phenytoin):
A single 600 mg oral dose of quinine sulfate increased the mean plasma Cmax,
and AUC0–24 of single oral doses of carbamazepine (200 mg) and phenobarbital
(120 mg) but not phenytoin (200 mg) in 8 healthy subjects. The mean AUC increases
of carbamazepine, phenobarbital and phenytoin were 104%, 81% and 4%, respectively;
the mean increases in Cmax were 56%, 53%, and 4%, respectively. Mean urinary
recoveries of the three antiepileptics over 24 hours were also profoundly increased
by quinine. If concomitant administration with carbamazepine or phenobarbital
cannot be avoided, frequent monitoring of anticonvulsant drug concentrations
is recommended. Additionally, patients should be monitored closely for adverse
reactions associated with these anticonvulsants. Carbamazepine, phenobarbital,
and phenytoin are CYP3A4 inducers and may decrease quinine plasma concentrations
if used concurrently with Qualaquin.
Astemizole (CYP3A4 substrate): Elevated plasma astemizole concentrations
were reported in a subject who experienced torsades de pointes after receiving
three doses of quinine sulfate for nocturnal leg cramps concomitantly with chronic
astemizole 10 mg/day. The concurrent use of Qualaquin with astemizole and other
CYP3A4 substrates with QT prolongation potential (e.g., cisapride, terfenadine,
halofantrine, pimozide and quinidine) should also be avoided (See WARNINGS).
Atorvastatin (CYP3A4 substrate): Rhabdomyolysis with acute renal
failure secondary to myoglobinuria was reported in a patient taking atorvastatin
administered with a single dose of quinine. Quinine may increase plasma concentrations
of atorvastatin, thereby increasing the risk of myopathy or rhabdomyolysis.
Thus, clinicians considering combined therapy of Qualaquin with atorvastatin
or other HMG-CoA reductase inhibitors (“statins”) that are CYP3A4 substrates
(e.g., simvastatin, lovastatin) should carefully weigh the potential benefits
and risks of each medication. If Qualaquin is used concomitantly with any of
these statins, lower starting and maintenance doses of the statin should be
considered. Patients should also be monitored closely for any signs or symptoms
of muscle pain, tenderness, or weakness, particularly during initial therapy.
If marked creatine phosphokinase (CPK) elevation occurs or myopathy (defined
as muscle aches or muscle weakness in conjunction with CPK values > 10 times
the upper limit of normal) is diagnosed or suspected, atorvastatin or other
statin should be discontinued.
Desipramine (CYP2D6 substrate): Quinine (750 mg/day for 2 days)
decreased the metabolism of desipramine in patients who were extensive CYP2D6
metabolizers, but had no effect in patients who were poor CYP2D6 metabolizers.
Lower doses (80 mg to 400 mg) of quinine did not significantly affect the pharmacokinetics
of other CYP2D6 substrates, namely, debrisoquine, dextromethorphan, and methoxyphenamine.
Although clinical drug interaction studies have not been performed, antimalarial
doses (greater than or equal to 600 mg) of quinine may inhibit the metabolism
of other drugs that are CYP2D6 substrates (e.g., flecainide, debrisoquine,
dextromethorphan, metoprolol, paroxetine). Patients taking medications that
are CYP2D6 substrates with Qualaquin should be monitored closely for adverse
reactions associated with these medications.
Digoxin: In 4 healthy subjects who received digoxin (0.5 to 0.75
mg/day) during treatment with quinine (750 mg/day), a 33% increase in mean steady
state AUC of digoxin and a 35% reduction in the steady-state biliary clearance
of digoxin were observed compared to digoxin alone. Thus, if Qualaquin is administered
to patients receiving digoxin, plasma digoxin concentrations should be closely
monitored, and the digoxin dose adjusted, as necessary (See PRECAUTIONS).
Halofantrine: Although not studied clinically, quinine was shown
to inhibit the metabolism of halofantrine in vitro using human liver
microsomes. Therefore, concomitant administration of Qualaquin is likely to
increase plasma halofantrine concentrations (See WARNINGS).
Mefloquine: In 7 healthy subjects who received mefloquine (750
mg) at 24 hours before an oral 600 mg dose of quinine sulfate, the AUC of mefloquine
was increased by 22% compared to mefloquine alone. In this study, the QTc interval
was significantly prolonged in the subjects who received mefloquine and quinine
sulfate 24 hours apart. The concomitant administration of mefloquine and Qualaquin
may produce electrocardiographic abnormalities (including QTc prolongation)
and may increase the risk of seizures (See WARNINGS).
Neuromuscular blocking agents (pancuronium, succinylcholine, tubocurarine):
In one report, quinine potentiated neuromuscular blockade in a patient who received
pancuronium during an operative procedure, and subsequently (3 hours after receiving
pancuronium) received quinine 1800 mg daily. Quinine may also enhance the neuromuscular
blocking effects of succinylcholine and tubocurarine (See WARNINGS).
Theophylline or aminophylline (CYP1A2 substrate): Although not
studied clinically, quinine has been shown to induce the activity of CYP1A2
in vitro using human hepatocytes. Therefore, concomitant administration
of Qualaquin and theophylline or aminophylline is likely to decrease the plasma
theophylline concentrations, possibly reducing the effect of theophylline or
aminophylline. Plasma theophylline concentrations should be monitored frequently
during concurrent therapy with theophylline or aminophylline and Qualaquin.
Warfarin and oral anticoagulants: Cinchona alkaloids, including
quinine, may have the potential to depress hepatic enzyme synthesis of vitamin
K-dependent coagulation pathway proteins and may enhance the action of warfarin
and other oral anticoagulants. Quinine may also interfere with the anticoagulant
effect of heparin. Thus, in patients receiving these anticoagulants, the prothrombin
time (PT), partial thromboplastin time (PTT), or international normalization
ratio (INR) should be closely monitored as appropriate, during concurrent therapy
with Qualaquin.
Drug/Laboratory Interactions: Quinine may produce an elevated value
for urinary 17-ketogenic steroids when the Zimmerman method is used.
Last updated on RxList: 1/12/2009