Main ingredients The main ingredient of this product is propafenone hydrochloride.
Characteristics This product is white or white-like.
Indications/Functions: Used for paroxysmal ventricular tachycardia and supraventricular tachycardia (including preexcitation syndrome).
Usage and dosage: 65438+2-4 tablets 0 time, 3-4 times a day. Therapeutic dosage: 6- 18 tablets per day, divided into 4-6 times. Maintenance amount: 6- 12 tablets a day, divided into 2-4 times. Because of its local anesthetic effect, it should be swallowed with drinks or food after meals and should not be chewed.
counteraction
1. There are few adverse reactions, mainly dry mouth and numbness of tongue and lips, which may be caused by local anesthesia. In addition, early adverse reactions include headache, dizziness and glare, followed by gastrointestinal dysfunction such as nausea, vomiting and constipation. And symptoms of atrioventricular block. Two cases of cholestatic liver injury were reported. After two weeks of continuous medication, the enzyme activities returned to normal 2~4 weeks after drug withdrawal. It is considered that this disease belongs to allergic reaction and individual factors.
2. No damage to lung, liver and hematopoietic system was found in the experiment. A few patients had mild reactions such as dry mouth, headache, dizziness and gastrointestinal discomfort, which generally disappeared after stopping the drug or reducing the amount. It has been reported that some patients have atrioventricular block, prolonged Q-T interval, slightly prolonged P-R interval and prolonged QRS time.
Patients with sinus node dysfunction, severe atrioventricular block and double bundle branch block without pacemaker protection, severe congestive heart failure, cardiogenic shock, severe hypotension and allergic to this product are prohibited.
Matters needing attention
1. Use with caution in patients with severe myocardial injury.
2. Use with caution in patients with severe bradycardia, hepatic and renal insufficiency and obvious hypotension.
3. In case of high sinus or atrioventricular block, sodium lactate, atropine, isoproterenol or m-hydroxyepinephrine can be injected intravenously for rescue.
The safety and effectiveness of this product for children are not clear.
The application of this drug in elderly patients will not increase the age-related side effects. However, the blood pressure of elderly patients may drop after taking the medicine. Moreover, elderly patients are prone to liver and kidney function damage, so use it with caution. The effective dose of drugs in elderly patients is lower than normal.
The safety and effectiveness of drugs used by pregnant women and lactating women are uncertain, so drugs should be used only when they are beneficial to the fetus. It is not clear whether the drug exists in breast milk, so it is recommended that lactating women stop using it.
Drug interaction combined with quinidine can slow down the metabolic process. Combined with local anesthetics, it increases the occurrence of side effects of central nervous system. Propafenone can increase the serum concentration of digoxin in a dose-dependent manner. The combination of propranolol and metoprolol can significantly increase the plasma concentration and clearance half-life, but has no effect on propafenone. When combined with warfarin, the plasma concentration and prothrombin time of warfarin can be increased. The combination with cimetidine can improve the steady-state level of propafenone in blood, but has no effect on its electrophysiological parameters.
The symptoms of drug overdose are most obvious 3 hours after drug overdose, including hypotension, drowsiness, bradycardia, intra-atrial and indoor conduction block, occasional convulsion or severe ventricular arrhythmia.
Pharmacology and toxicology 1. Pharmacology: (1) This product belongs to Ic antiarrhythmic drug (that is, it directly acts on cell membrane). The experimental results on isolated animal myocardium show that 0.5- 1μg/min can reduce systolic depolarization, thus prolonging conduction, slightly prolonging the duration of action potential and effective refractory period, increasing the threshold potential of myocardial cells and obviously reducing the spontaneous excitability of myocardium. It not only acts on atria and ventricles (mainly on Purkinje fibers, but has little effect on myocardium), but also on the formation and conduction of excitement. Clinical data show that the therapeutic dose (6 tablets orally and 30mg intravenously) can reduce myocardial stress, with lasting effect, increase PQ and QRS, prolong the effective refractory period of atrium and atrioventricular node, and has antagonistic effect on various types of experimental arrhythmia. The antiarrhythmic effect is related to its membrane stability and competitive blocking effect. There is still weak calcium antagonism (weaker than verapamil 100 times) and mild myocardial inhibition. The end-stage diastolic pressure increases and the cardiac output decreases, all of which are directly proportional to the drug dose. It also has a mild effect of lowering blood pressure and slowing heart rate. (2) In vitro experiments show that propafenone can relax coronary artery and bronchial smooth muscle. (3) It has similar local anesthetic effect to procaine. 2. Toxicology: Rats were given 18-360mg/kg/ day (the maximum recommended dose for adults was 12-24 times) for six months, with abnormal renal function and inflammatory and non-inflammatory reactions in renal tubules and renal interstitium. Liver steatosis can be found when rats take 1.9 times the maximum recommended dose for adults for a long time.
Pharmacokinetics of absorption from gastrointestinal tract after oral administration is good, and the antiarrhythmic effect reaches its peak in 2~3 hours after administration, and the effect can last for more than 8 hours. Its bioavailability is dose-dependent, for example, 2 tablets of propafenone are 3.4%, while 6 tablets are 10.6%. The binding rate of this product with plasma protein is high, reaching 93%, and the bioavailability will increase with the increase of dose. The decline of liver function will also increase the bioavailability of drugs, and the clearance of propafenone will be slow when liver function is seriously damaged. The pharmacokinetic curve of propafenone is nonlinear. The half-life of this medicine is 3.5-4 hours. This product is excreted by the kidney, mainly metabolites, and a small part (1%) is prototype. Can't be excreted by dialysis.