Felodipine is equal to amlodipine, nifedipine, and nitrite, and is a calcium channel blocker. It has a good effect of dilating arteries and lowering blood pressure. It can be used preferentially for the elderly with isolated systolic blood pressure. patient.
I. Usage and dosage of felodipine
Felodipine tablets: The starting dose is 2.5 mg each time, twice daily. After 2 weeks, it can be increased to 10 mg daily. Felodipine Sustained Release Tablets (Boeding, Linuo, etc.): The starting dose is 5 mg each time, once daily. The general daily dose does not exceed 20mg.
– Sustained release tablets should not be milled, crushed or chewed.
II. Usage in liver and kidney injury
The bioavailability of felodipine after a single oral dose of felodipine in patients with cirrhosis was not significantly different from that of a single oral dose of felodipine in healthy subjects, but the maximum plasma concentration in cirrhotic patients was approximately a healthy test. 2 times.
– The initial dose of liver injury patients is 2.5mg per day, kidney injury does not need to adjust the dose.
III. Most common adverse reactions
Foot and ankle edema is a common adverse reaction to calcium channel blockers (felodipine, amlodipine, nifedipine, and nitrendipine). It usually occurs 2 weeks or more after the start of treatment.
The edema caused by calcium channel blockers is mainly due to the expansion of the precapillary arterioles rather than the retention of fluids. Therefore, taking diuretics is not effective.
Peripheral edema can be relieved by raising the foot or by reducing the amount of medication (patients should not arbitrarily reduce the dose). However, if the symptoms persist, other types of antihypertensive drugs should be used instead.
Common felodipine cardiovascular system adverse reactions are tachycardia or palpitations, with the increase in the amount or plasma concentration, the incidence increased.
IV. Best medication time
Felodipine can be absorbed rapidly and completely by the gastrointestinal tract, but there is first-pass metabolism (in the intestine, liver, metabolized by CYP3A4 enzyme), and the bioavailability is only 15%.
The bioavailability of felodipine is strongly influenced by food, and the peak concentration can be increased by 60% when given a high-fat meal or carbohydrate diet.
– Felodipine sustained-release tablets should be taken on an empty stomach in the morning (felodipine can cause nausea, abdominal pain and other gastrointestinal reactions, but the incidence is less than 1%).
V. Avoid eating grapefruit juice during medication
The flavonoids in grapefruit juice (grapefruit) inhibit CYP3A4.
– Grapefruit juice can increase the peak concentration and bioavailability of felodipine by nearly 2 times. Therefore, during the course of medication, patients should avoid eating grapefruit or grapefruit juice.
VI. Avoid combination with the following drugs
1. Avoid combination with CYP3A4 inducer
Anti-epileptic drugs (carbamazepine, phenytoin, phenobarbital) and anti-tuberculosis drugs (rifampicin) are CYP3A4 inducers, which can significantly increase the metabolism of felodipine and reduce the bioavailability of felodipine by 93%. The concentration decreased by 82%.
2. Avoid combination with CYP3A4 inhibitors
Macrolide antibiotics (erythromycin, clarithromycin), imidazole antifungal (itraconazole, fluconazole), H2 receptor inhibitor (cimetidine), immunosuppressive (cyclosporine ) is a CYP3A4 inhibitor that inhibits felodipine metabolism and increases felodipine toxicity.
– Cimetidine: Inhibition of in vivo metabolism of felodipine and nifedipine can increase the peak concentration and bioavailability of felodipine by approximately 55%, and increase the bioavailability of nifedipine by 77% to 99%. %.
– Amiodarone: Inhibition of fenodipine in vivo metabolism; combination of felodipine and amiodarone can further slow down the sinus rhythm and aggravate atrioventricular block.
VII. Use caution with the following drugs
1. Beta blocker
Felodipine is well tolerated with beta-blockers and is beneficial for the treatment of angina and hypertension. However, in patients with left ventricular dysfunction, arrhythmia, or aortic stenosis, β-blockers combined with dihydropyridine calcium antagonists can cause significant hypotension and cardiac depression.
According to reports, felodipine can increase the peak concentration of digoxin, but the steady state digoxin concentration is not affected, and this interaction is of little clinical significance.
Some studies have suggested that felodipine can reduce the plasma concentration of theophylline but has little clinical significance.
When felodipine is combined with magnesium, it causes significant hypotension and neuromuscular blockade. Therefore, blood pressure should be closely monitored when used together.
5. Non-steroidal anti-inflammatory drugs
Non-steroidal anti-inflammatory drugs and calcium antagonists may increase the possibility of gastrointestinal bleeding, and the signs of gastrointestinal bleeding should be closely monitored in combination.
6. Oral anticoagulants
Oral anticoagulant drugs and calcium antagonists may increase the possibility of gastrointestinal bleeding. When combined, the signs of gastrointestinal bleeding should be closely monitored.