A1,
A2,
B,
C1,
C2,
D,
E,
F,
G-H,
I-K,
L,
M,
N,
O,
P1,
P2,
Q-R,
S,
T,
U-V,
W-Z
Flagyl Side Effects, and Drug Interactions - Metronidazole (oral)
Flagyl Side Effects, and Drug Interactions - Metronidazole (oral)
SIDE EFFECTS
Two serious adverse reactions reported in patients treated with metronidazole
have been convulsive seizures and peripheral neuropathy, the latter characterized
mainly by numbness or paresthesia of an extremity. Since persistent peripheral
neuropathy has been reported some patients receiving prolonged administration
of metronidazole, patients should be specifically warned about these reactions
and should be told to stop the drug and report immediately to their physicians
if any neurologic symptoms occur.
The most common adverse reactions reported have been referable to the
gastrointestinal tract, particularly nausea, reported by about 12% of
patients, sometimes accompanied by headache, anorexia, and occasionally
vomiting; diarrhea; epigastric distress; and abdominal cramping. Constipation
has also been reported.
The following reactions have also been reported during treatment with
metronidazole:
Mouth: A sharp, unpleasant metallic taste is not unusual. Furry
tongue, glossitis, and stomatitis have occurred; these may be associated
with a sudden overgrowth of Candida which may occur during therapy.
Hematopoietic: Reversible neutropenia (leukopenia); rarely reversible
thrombocytopenia.
Cardiovascular: Flattening of the T-wave may be seen in electrocardiographic
tracings.
Central Nervous System: Convulsive seizures, peripheral neuropathy,
dizziness, vertigo, incoordination, ataxia, confusion, irritability, depression,
weakness, and insomnia.
Hypersensitivity: Urticaria, erythematosus rash, flushing, nasal
congestion, dryness of the mouth (or vagina or vulva) and fever.
Renal: Dysuria, cystitis, polyuria, incontinence, and a sense
of pelvic pressure. Instances of darkened urine have been reported by
approximately one patient in 100,00. Although the pigment which is probably
responsible for this phenomenon has not been positively identified, it
is almost certainly a metabolite of metronidazole and seems to have no
clinical significance.
Other: Proliferation of Candida in the vagina, dyspareunia,
decrease of libido, proctitis, and fleeting joint pains sometimes resembling
'serum sickness'. If patients receiving metronidazole drink alcoholic
beverages, they may experience abdominal distress, nausea, vomiting, flushing,
or headache. A modification of the taste of alcoholic beverages has also
been reported. Rare cases of pancreatitis, which generally abated on withdrawal
of the drug, have been reported.
Crohn's disease patients are known to have an increased incidence of
gastrointestinal and certain extraintestinal cancers. There have been
some reports in the medical literature of breast and colon cancer in Crohn's
disease patients who have been treated with metronidazole at high doses
for extended periods of time. A cause and effect relationship has not
been established. Crohn's disease is not an approved indication for metronidazole
DRUG INTERACTIONS
Metronidazole has been reported to potentiate the anticoagulant effect
of warfarin and other oral coumarin anticoagulants, resulting in a prolongation
of prothrombin time. This possible drug interaction should be considered
when metronidazole is prescribed for patients on this type of anticoagulant
therapy.
The simultaneous administration of drugs that induce microsomal liver
enzymes, such as phenytoin or phenobarbital, may accelerate the elimination
of metronidazole, resulting in reduced plasma levels; impaired clearance
of phenytoin has also been reported.
The simultaneous administration of drugs that decrease microsomal liver
enzyme activity, such as cimetidine, may prolong the half-life and decrease
plasma clearance of metronidazole. In patients stabilized on relatively
high doses of lithium, short-term metronidazole therapy has been associated
with elevation of serum lithium and in a few cases, signs of lithium toxicity.
Serum lithium and serum creatinine levels should be obtained several days
after beginning metronidazole to detect any increase that may precede
clinical symptoms of lithium intoxication.
Alcoholic beverages should not be consumed during metronidazole therapy
and for at least one day afterward because abdominal cramps, nausea, vomiting,
headaches, and flushing may occur.
Psychotic reactions have been reported in alcoholic patients who are
using metronidazole and disulfiram concurrently. Metronidazole should
not be given to patients who have taken disulfiram within the last two
weeks.
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