Felodil XR - 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.
Felodil XR is a medicine that contains an active ingredient called felodipine. It belongs to a group of dihydropyridine calcium antagonists. It works by preventing the entry of calcium ions into the smooth muscles in blood vessels and heart, causing muscle relaxation and consequent dilatation of the blood vessels. As other dihydropyridine calcium antagonists, Felodil XR also exerts greater effects on blood vessels than on the heart.
Dilation of peripheral blood vessel reduces peripheral vascular resistance, which leads to a reduction in blood pressure and reflex increase in heart rate (by 5-10 beats per minute). Increased heart rate can be blocked with beta blockers.
Felodil XR extended release tablets are used to treat hypertension and stable angina pectoris.
The results of the clinical study that tested the efficacy of felodipine as monotherapy in hypertensive patients after eight weeks of regular taking has shown that patients who were receiving 2.5 mg daily had an average reduction of systolic blood pressure by 9.4% and diastolic pressure by 4.7%, while patients who were receiving 5 mg daily had an average reduction of systolic blood pressure by 9.5% and diastolic pressure by 6.3%. Patients who were receiving 10 mg daily had an average reduction of systolic blood pressure by 18.0% and diastolic pressure by 10.8%.
Felodil XR can be combined with other antihypertensive drugs.
Like all other antihypertensive drugs, Felodil XR can also cause hypotension and consequent dizziness and temporary loss of consciousness (syncope). If you notice that you often feel dizzy or lightheaded, you should inform your doctor.
Because Felodil XR exhibits a negative inotropic effect, caution should be exercised if this medicine is used in patients with heart failure. Studies in a small number of patients with NYHA Class II and III have not demonstrated a negative inotropic effect of felodipine, but safety of its use in patients with heart failure has not been established.
Mild peripheral edema is the most commonly reported adverse reaction and it occurs more commonly in elderly patients who are taking high doses. It usually occurs within 15-20 days of the initiation of Felodil XR therapy. Inform your doctor if you notice swelling (edema).
Felodil XR should not be used:
- In patients who have recently had a heart attack.
- In patients with severe heart conditions.
- In patients who have an unstable angina pectoris.
- In patients with cardiogenic shock.
Caution should also be exercised in patients with impaired hepatic function and in patients with tachycardia (rapid heart rate).
Felodil XR, Pregnancy and Breastfeeding
According to the FDA, this drug is classified into the pregnancy category C, since studies in rabbits that investigated the use of doses that are 0.8 to 8 times higher than the maximum recommended doses in humans have shown that this drug reduces the ossification of distal phalanges in fetus. It is assumed that mechanism that causes this birth defect is disturbed uterine blood flow. Studies in rats have not demonstrated this side effect, while studies on monkeys have shown that this drug may change the position of distal phalanges in the fetus.
One cohort study conducted in Sweden revealed that 3 out of 217 babies whose mothers took calcium channel blockers during pregnancy were born with congenital heart anomalies, which is not considered as statistically significant.
Another case-control study conducted in Hungary on 586 women who took calcium blockers during pregnancy revealed the occurrence of congenital malformations in 17 babies, which is also not considered as statistically significant.
Therefore, studies conducted so far have not shown an increased risk of major malformations, but there are still not enough well-controlled clinical studies to confirm the safety of this drug during pregnancy. Consult your doctor before taking this medicine during pregnancy.
LactMed (drug and lactation database) and American Academy of Pediatrics state that calcium blockers can be safely administered during breastfeeding. However, the drug manufacturer and FDA advise that doctor should decide whether to stop the use of the drug or breastfeeding because of possible serious side effects that may occur in infants.
The usual dose ranges from 2.5 to 10 mg per day. Administration of doses greater than 10 mg daily showed a significant reduction in blood pressure, but also a significantly higher potential for peripheral edema. Therefore, administration of doses greater than 10 mg is not recommended.
The usual starting dose is 5 mg daily and depending on the clinical response, the doctor may decide to reduce your dose to 2.5 mg daily or increase it to 10 mg per day.
Patients above the age of 65 as well as patients with impaired hepatic function should start treatment with lower dose (2.5 mg daily).
Felodil XR extended release tablets should be taken on an empty stomach or with a light meal. Taking tablets with a meal rich in carbohydrates or fats increases the maximum concentration of the drug which increases the risk of side effects.
Do not take Feloxil XR extended release tablets concomitantly with grapefruit juice because it increases the concentration of Felodil XR in the blood by 50%.
Felodil XR should not be used concurrently with the following medicines:
- Dolasetron (a medicine used to treat nausea and vomiting induced by chemotherapy). Simultaneous administration increases the risk of arrhythmias.
- Edoxaban (an anticoagulant drug used to prevent thrombus formation in patients with atrial fibrillation). Simultaneous administration increases the risk of bleeding.
- Rifampin, rifampicin and rifabutin (medicines used to treat tuberculosis). These drugs significantly reduce the concentration of Felodil XR in the blood which reduces its effects.
- Antifungal medications (itraconazole and ketoconazole). These medicines significantly increase the concentration of Felodil XR in the blood, which increases the risk of side effects (hypotension, arrhythmias and edema).
- Tizanidine (a medicine used to treat muscle spasms). Tizanidine may potentiate the antihypertensive effect of Felodil XR, which may lead to hypotension
- Venetoclax (a medicine used to treat chronic lymphocytic leukemia). Felodil XR increases the concentration of venetoclax in the blood which can lead to kidney damage and may have fatal outcome!
- Erythromycin (antibiotic). This medicine can increase the level of Felodil XR in the blood which increases the risk of side effects.
HIV protease inhibitors that are used to treat HIV, such as:
- Antiepileptic medications, such as: carbamazepine and phenytoin. These drugs reduce the concentration of Felodil XR in the blood and therefore reduce its effectiveness in lowering blood pressure.
- Warfarin - a blood thinner. Simultaneous administration increases the risk of bleeding.
- Tacrolimus and cyclosporine.
Felodil XR should not be administered concurrently with preparations containing St John's wort or with grapefruit juice.
Possible side effects of Felodil XR extended release tablets include:
- Peripheral edema (occurs most commonly on the legs).
- Tachycardia (rapid heart rate).
- Abdominal pain.
- Dizziness and syncope.
- Muscle pain.
- Joint pain.
- Frequent urination.
- Allergic reactions.
- American Academy of Pediatrics Committee on Drugs: the transfer of drugs and other chemicals into human milk. Pediatrics. 1994: 93 (1):137-50.
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