OVERDOSE
In studies with healthy volunteers of single doses up
to 800 mg, adverse events were similar to those seen at
lower doses but incidence rates were increased.
In cases of overdose, standard supportive measures should
be adopted as required. Renal dialysis is not expected
to accelerate clearance as sildenafil is highly bound
to plasma proteins and it is not eliminated in the urine.
CONTRAINDICATIONS
Consistent with its known effects on the nitric oxide/cGMP
pathway (see CLINICAL PHARMACOLOGY), sildenafil citrate
was shown to potentiate the hypotensive effects of nitrates,
and its administration to patients who are using organic
nitrates either regularly and/or intermittently in any
form is therefore contraindicated.
After patients have taken sildenafil
citrate, it is unknown when nitrates, if necessary, can
be safely administered. Based on the pharmacokinetic profile
of a single 100 mg oral dose given to healthy normal volunteers,
the plasma levels of sildenafil at 24 hours post dose
are approximately 2 ng/mL (compared to peak plasma levels
of approximately 440 ng/mL) (see CLINICAL PHARMACOLOGY,
Pharmacokinetics and Metabolism). In the following patients:
age >65, hepatic impairment (e.g., cirrhosis), severe
renal impairment (e.g., creatine clearance <30 mL/min),
and concomitant use of potent cytochrome P450 3A4 inhibitors
(erythromycin), plasma levels of sildenafil at 24 hours
post dose have been found to be 3 to 8 times higher than
those seen in healthy volunteers. Although plasma levels
of sildenafil at 24 hours post dose are much lower than
at peak concentration, it is unknown whether nitrates
can be safely coadministered at this time point.
Sildenafil citrate is contraindicated
in patients with a known hypersensitivity to any component
of the tablet.
|
