FELODIPINE ER

Felodipine 5mg, Oral tablet, extended release

Grapefruit juice

· Severity: Major

· Notes for Consumers: Use caution when taking grapefruit juice with Felodipine since it may increase the effects of Felodipine. If the blood pressure drops too low while taking this medicine, you may become dizzy or feel faint; do not stand or sit up too quickly. Contact your prescriber if you have dizziness which does not go away while taking this medicine. If you notice new or increased swelling of your legs or ankles, tell your health care provider.

· Notes for Professionals: Clinicians should be aware that grapefruit juice (food) interactions with some calcium channel blockers are possible. Grapefruit juice inhibits the cytochrome P-450 3A4 isozyme in the gut wall. Grapefruit juice contains furanocoumarins that are metabolized by CYP3A4 to reactive intermediates. These intermediates form a covalent bond to the active site of the CYP3A4 enzyme, causing irreversible inactivation (mechanism-based inhibition). Consequently, CYP3A4 activity in the gut wall is inhibited until de novo synthesis returns the enzyme to its previous level. Coadministration of oral felodipine with 200 ml to 250 ml of grapefruit juice resulted in an average systemic drug concentration that was 3-fold that seen with water; the AUC and Cmax were increased, but the half-life was not prolonged. The increase in felodipine bioavailability is most likely due to inhibition of CYP3A4 isoenzymes, and resulting reduced first-pass drug metabolism. The pharmacokinetics are affected by the interval between the ingestion of grapefruit and the adminstration of felodipine. For example, the closer the time in between the ingestion of felodipine and the grapefruit juice, the greater the effect of the interaction. In addition, repeated ingestion of grapefruit (200 ml of juice, 3 times a day for 7 days) doubled the size of the interaction for 24 hours, consistent with a cumulative inhibitory action. Patient vulnerability to this interaction varies markedly, probably due the patient's levels of CYP3A4 in the small intestine. Elderly patients have the greatest possibility of ingesting grapefruit and interacting medications and are the most vulnerable to the adverse clinical consequences. According to the manufacturer of felodipine, caution should be used when coadministering felodipine with grapefruit juice. Amlodipine may be an alternative in certain patients since it may not interact or may have a minor pharmacokinetic interaction with grapefuit juice.

<b>DISCLAIMER:</b><em> This drug information content is provided for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Patients should always consult their physician with any questions regarding a medical condition and to obtain medical advice and treatment. Drug information is sourced from GSDD (Gold Standard Drug Database ) provided by Elsevier.</em>