Felodur ER - Dosage | Interactions | Effects
This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.
Felodur ER is a drug containing an active substance called felodipine. It belongs to a group of medicines called calcium blockers. Chemically, it is classified into dihydropyridine class of calcium blockers. It works by reducing the contractility of smooth muscles located in the blood vessel wall, which reduces peripheral vascular resistance and thus lower blood pressure. In vitro studies have shown that it exhibits a negative inotropic effect, but for now there is no in vivo study to confirm this effect.
It also exhibits a mild diuretic effect, but the anti-hypertensive effect occur primarily due to the reduction of peripheral vascular resistance.
It is used for the treatment of hypertension.
Blood pressure control is an important factor in the prevention of heart attack and stroke regardless of whether patients experience symptoms or not.
Studies have shown that this medicine can lower systolic blood pressure by up to 18% and diastolic by 10% if administered at a dose of 10 mg daily as monotherapy.
Felodur ER is completely absorbed after oral administration and then undergoes first pass metabolism through the liver. The bioavailability of felodipine is on average 20%, but varies depending on food intake. If taken with a light meal (e.g. cereals), then pharmacokinetics of felodipine remains unchanged, but if taken with foods rich in fats or carbohydrates, then the maximum concentration can be increased by 60%. For this reason, it is recommended to take Felodur ER tablets on an empty stomach, or at least two hours before or after a meal.
Over 99% of this drug is bound to plasma proteins. The elimination half-life is 11-16 hours while the antihypertensive effects lasts about 24 hours, which is why this drug is administered once a day.
Felodur ER should not be used in patients who have a known hypersensitivity / allergic reaction to the active substance felodipine or other dihydropyridine (e.g. amlodipine and nifedipine).
One double blind study conducted in the UK has shown that this drug has no beneficial effects in patients with heart failure, and therefore it should be used with extra precaution in such patients.
According to Patient Information Leaflet (PIL), its use should also be avoided in patients who have had a recent heart attack, have cardiogenic shock, or an unstable angina pectoris.
LiverTox states that for 20 years of the clinical use, there are still no reported cases of felodipine-induced liver injury, and that felodpine was only associated with mild, transient and clinically insignificant increase in transaminase blood levels (transaminase levels did not differ significantly from placebo).
However, PIL states that Felodur ER should be used cautiously in patients with liver damage, probably because this drug is predominantly metabolized via liver enzyme called CYP3A4. The FDA recommends reducing initial dose to 2.5 mg daily in patients with impaired liver function.
Peripheral edema is one of the most commonly reported adverse reactions. Studies revealed that patients over 60 years of age who take high doses of this drug are at higher risk of developing this side effect.
Patients with tachycardia should cautiously apply this drug, as studies have shown that Felodur ER can increase heart rate.
Felodur ER, Pregnancy and Breastfeeding
Animal studies revealed that this drug can cause digital anomalies in newborns, and its use during pregnancy should be avoided.
It is not known whether felodipine is excreted into breast milk or not, but its use during lactation should be avoided due to the possible occurrence of adverse effects.
The usual starting dose is 5 mg once a day. The maintenance dose ranges from 2.5 to 10 mg once a day depending on the patient's response to the therapy.
Patients who have impaired liver function and patients older than 65 years should start therapy with a lower dose (2.5 mg daily).
No dose adjustment is required in patients with impaired renal function.
Felodur ER extended release tablets should be taken two hours before or two hours after the meal.
Felodur ER should not be used concurrently with the following medicines:
- Cimetidine (drug used to treat the ulcer).
- Phenobarbital (drug used to treat epilepsy).
- Erythromycin (drug used to treat bacterial infections). Erythromycin increases plasma concentrations of Felodur ER, which increases the risk of side effects.
- Itraconazole, fluconazole (Ozole, Dizole) and ketoconazole - medicines used to treat fungal infections. Felodur ER increases plasma concentrations of these drugs and increases the risk of side effects (e.g. torsades de pointes - life-threatening arrhythmia).
- Medicines used to treat epilepsy, such as: carbamazepine and phenytoin. These drugs are inducers of CYP3A4 enzyme, and thus reduce the level of Felodur ER in the blood, which reduces its antihypertensive efficacy.
- Tacrolimus (immunosuppressant drug most commonly used after kidney or liver transplantation). Felodur ER increases the concentration of this medicine in the blood which increases the risk of side effects.
- St John's wort preparations used in the treatment of anxiety and depression. Felodur ER reduces the efficacy of these preparations.
- Rifabutin, rifampicin and rifampin (antibiotics used to treat tuberculosis). These drugs are potent inhibitors of CYP3A4 enzymes, thus reducing the efficacy of Felodur ER.
- Anticoagulant drugs (e.g. endoxaban and warfarin). Felodur ER increases the plasma concentration of these drugs, increasing the risk of side effects.
- Dolasetron - drug used to treat chemotherapy-induced nausea. Simultaneous administration increases the risk of irregular heartbeat.
- Venetoclax (drug used to treat CLL - chronic lymphocytic leukemia). Felodur ER may increase the concentration of this medicine in the blood, resulting in an increased risk of bone marrow depression, anemia and thrombocytopenia.
- Tizanidine (drug used to treat muscle spasticity). Tizanidine may increase the antihypertensive effects of Felodur ER medication.
- Cyclosporine (immunosuppressive drug).
Felodur ER is associated with the following side effects:
- Tingling, pain, numbness and burning in your fingers.
- Rapid heart rate (tachycardia).
- Warm sensation.
- Loss of consciousness.
- Swelling of the gums.
- Mild increase in liver enzyme levels.
- Allergic reactions.
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