Quinidine sulfate tablets

This product is a Class Ia antiarrhythmic drug, which has a direct effect on the cell membrane, mainly inhibiting the transmembrane movement of sodium ions and affecting the 0 phase of the action potential. It inhibits the autonomy of the myocardium, especially the autonomy of ectopic excitation points, reduces the conduction velocity, prolongs the effective refractory period, reduces excitability, and prolongs the refractory period of the atria more significantly than the ventricles, shortens the refractory period of the atrioventricular junction, and increases the fibrillation threshold of the atrial and ventricular muscles. Secondly, it inhibits the influx of calcium ions and reduces the contractility of the myocardium. It indirectly affects the heart through anticholinergic effects. Large doses can block α receptors, produce vasodilation and hypotension. The effective blood concentration of quinidine is 3-6 mg/L, and serious adverse reactions may occur above 8 mg/L.

The chemical name of this product is: (9S)-6prime;-methoxy-deoxycinchonin-9-ol sulfate dihydrate.

This product is a sugar-coated tablet, which appears white after removing the sugar coating.

It is mainly used for the maintenance treatment of atrial fibrillation or atrial flutter after electrical cardioversion. Although it is effective for atrial premature beats, paroxysmal supraventricular tachycardia, preexcitation syndrome with supraventricular arrhythmia, ventricular premature beats, ventricular tachycardia, and has the effect of converting atrial fibrillation or atrial flutter, it is rarely used now due to many adverse reactions.

Adults should first try taking 0.2g to observe whether there are allergic and idiosyncratic reactions. Common dosage for adults: 0.2-0.3g at a time, 3-4 times a day. For cardioversion of atrial fibrillation or atrial flutter, 0.2g on the first day, once every 2 hours, for 5 consecutive times; if there are no adverse reactions, increase to 0.3g each time on the second day, and 0.4g each time on the third day, once every 2 hours, for 5 consecutive times. The total daily amount should not exceed 2.4g. After sinus rhythm is restored, change to a maintenance dose of 0.2-0.3g at a time, 3-4 times a day. The maximum dosage for adult prescription: 3g per day (generally not more than 2.4g per day), which should be given in divided doses.

This product has a low therapeutic index, and about 1/3 of patients experience adverse reactions. 1 Cardiovascular: This product has a proarrhythmic effect, causing cardiac arrest and conduction block, which is more common in patients with existing heart disease. Ventricular premature beats, ventricular tachycardia and ventricular fibrillation may also occur. The electrocardiogram may show a prolonged P-R interval and a widened QRS wave, which is generally related to the dose. It can significantly prolong the Q-T interval of the electrocardiogram, induce ventricular tachycardia (torsades de pointes) or ventricular fibrillation, and may stop spontaneously repeatedly, accompanied by syncope during attacks. This effect is unrelated to the dose and may occur when the blood drug concentration is still within the therapeutic range or below. This product can cause vasodilation and produce hypotension, and vasculitis may occur in some cases. 2 Gastrointestinal adverse reactions: very common. Including nausea, vomiting, painful cramps, diarrhea, loss of appetite

Patients who are allergic to the drug or who have developed thrombocytopenic purpura after using the drug are contraindicated. The drug is contraindicated for patients with Ⅱ or Ⅲ degree atrioventricular block and sick sinus syndrome without pacemaker protection.

1. When used in combination with other antiarrhythmic drugs, the effects may be additive. Verapamil and amiodarone may increase the blood concentration of this product. 2. When used in combination with oral anticoagulants, prothrombin may be further reduced, and the binding of this product to proteins may also be reduced. Therefore, it is necessary to pay attention to adjusting the dosage during combined use and after drug withdrawal. 3. Phenobarbital and phenytoin sodium may increase the intrahepatic metabolism of this product and shorten the plasma half-life. The dosage should be adjusted as appropriate. 4. This product may increase the serum concentration of digoxin to a toxic level, and may also increase the serum concentration of digitalis glycosides. Therefore, the blood concentration should be monitored and the dosage adjusted. This product may aggravate arrhythmias when digitalis is overdosed. 5. When used in combination with anticholinergic drugs, the anticholinergic effect may be increased. 6. It weakens the effect of cholinergic drugs, and the dosage should be adjusted as needed. 7. This product may enhance and prolong the respiratory depressant effect of neuromuscular blockers, especially tubocurarine, succinylcholine and pancuronium bromide. 8 Alkalinizing drugs such as acetazolamide, large amounts of lemon juice, antacids or bicarbonates can increase the reabsorption of this product by the renal tubules, so that toxic reactions occur at commonly used doses. 9 When used in combination with antihypertensive drugs, vasodilators and beta-blockers, this product can intensify the antihypertensive and vasodilatory effects; when used in combination with beta-blockers, it can also aggravate the inhibitory effects on the sinoatrial node and atrioventricular node. 10 Fopicolide can increase the metabolism of this product and reduce the blood concentration of the drug. 11 Proterenol may aggravate arrhythmias caused by an overdose of this product, but it is beneficial for torsades de pointes caused by prolonged Q-T interval.

Keep in a light-proof and airtight container.

0.2g