OVERDOSE
Experience with nifedipine overdosage is limited. Generally
overdosage with nifedipine leading to pronounced hypotension
calls for active cardiovascular support including monitoring
of cardiovascular and respiratory function, elevation
of extremities, judicious use of calcium infusion, pressor
agents, and fluids. Clearance of nifedipine would be expected
to be prolonged in patients with impaired liver function.
Since nifedipine is highly protein-bound, dialysis is
not likely to be of any benefit.
Additional Information for Extended Release Tablets
There has been one reported case of massive overdosage
with nifedipine extended release tablets. The main effects
of ingestion of approximately 4800 mg of nifedipine in
a young man attempting suicide as a result of cocaine-induced
depression were initial dizziness, palpitations, flushing,
and nervousness. Within several hours of ingestion, nausea,
vomiting, and generalized edema developed. No significant
hypotension was apparent at presentation, 18 hours post-ingestion.
Electrolyte abnormalities consisted of a mild, transient
elevation of serum creatinine, and modest elevations of
LDH and CPK, but normal SGOT. Vital signs remained stable,
no electrocardiographic abnormalities were noted and renal
function returned to normal within 24 to 48 hours with
routine supportive measures alone. No prolonged sequelae
were observed.
The effect of a single 900 mg ingestion of nifedipine
capsules in a depressed anginal patient also on tricyclic
antidepressants was loss of consciousness within 30 minutes
of ingestion, and profound hypotension, which responded
to calcium infusion, pressor agents, and fluid replacement.
A variety of ECG abnormalities were seen in this patient
with a history of bundle branch block, including sinus
bradycardia and varying degrees of AV block. These dictated
the prophylactic placement of a temporary ventricular
pacemaker, but otherwise resolved spontaneously. Significant
hyperglycemia was seen initially in this patient, but
plasma glucose levels rapidly normalized without further
treatment.
A young hypertensive patient with advanced renal failure
ingested 280 mg of nifedipine capsules at one time, with
resulting marked hypotension responding to calcium infusion
and fluids. No AV conduction abnormalities, arrhythmias,
or pronounced changes in heart rate were noted, nor was
there any further deterioration in renal function.
CONTRAINDICATIONS
Known hypersensitivity reaction to nifedipine.
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