LASIX® is a diuretic which is an anthranilic acid derivative. LASIX tablets for oral administration contain furosemide as the active ingredient and the following inactive ingredients: lactose monohydrate NF, magnesium stearate NF, starch NF, talc USP, and colloidal silicon dioxide NF. Chemically, it is 4-chloro-N-furfuryl-5-sulfamoylanthranilic acid. LASIX is available as white tablets for oral administration in dosage strengths of 20, 40 and 80 mg. Furosemide is a white to off-white odorless crystalline powder. It is practically insoluble in water, sparingly soluble in alcohol, freely soluble in dilute alkali solutions and insoluble in dilute acids.The CAS Registry Number is 54-31-9.

The structural formula is as follows:
Common uses
This medicine is a loop diuretic used to treat high blood pressure, congestive heart failure, and swelling due to excess body water. It may also be used to treat other conditions as determined by your doctor.
Before using
Warning: this drug is a strong “water pill” (diuretic). Using too much of this drug can lead to serious water and mineral loss. Therefore, it is important you be monitored by your doctor. Promptly notify your doctor if you become very thirsty, have a dry mouth, become confused, or develop muscle cramps/weakness.Some medicines or medical conditions may interact with this medicine. Inform your doctor or pharmacist of all prescription and over-the-counter medicine that you are taking. Additional monitoring of your dose or condition may be needed if you are taking anticoagulants, parenteral aminoglycosides, chloral hydrate, cisplatin, digitoxin, digoxin, ginseng, or indomethacin. Inform your doctor of any other medical conditions, allergies, pregnancy, or breast-feeding. Contact your doctor or pharmacist if you have any questions or concerns about taking this medicine.
Directions
Follow the directions for using this medicine provided by your doctor. This medicine may be taken on an empty stomach or with food. When you first start taking this medicine, it may cause an increase in urine or in frequency of urination. If you are taking 1 dose daily, take it in the morning to prevent this medicine from affecting your sleep. If you are taking more than 1 dose, take the last dose no later than 6 pm.Store this medicine at room temperature in a tightly-closed container, away from heat and light. If you miss a dose of this medicine, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.
Cautions
Do not take this medicine if you have had an allergic reaction to it or are allergic to any ingredient in this product. Laboratory and/or medical tests, including blood electrolytes, kidney function, and blood glucose may be performed to monitor your progress or to check for side effects. Keep all doctor and laboratory appointments while you are taking this medicine. Your doctor may have also prescribed a potassium supplement for you. If so, follow the dosing carefully. Do not start taking additional potassium on your own or change your diet to include more potassium without first checking with your doctor. Do not drive, operate machinery, or do anything else that could be dangerous until you know how you react to this medicine. Using this medicine alone, with other medicines, or with alcohol may lessen your ability to drive or to perform other potentially dangerous tasks.This medicine may cause dizziness, lightheadedness, or fainting. Alcohol, hot weather, exercise, and fever can increase these effects. To prevent them, sit up or stand slowly, especially in the morning. Also, sit or lie down at the first sign of dizziness, lightheadedness, or weakness. This medicine may cause increased sensitivity to the sun. Avoid exposure to the sun, sunlamps, or tanning booths until you know how you react to this medicine. Use a sunscreen or protective clothing if you must be outside for a prolonged period. Before you begin taking any new medicine, either prescription or over-the-counter, check with your doctor or pharmacist.
For women: if you plan on becoming pregnant, discuss with your doctor the benefits and risks of using this medicine during pregnancy. This medicine is excreted in breast milk. If you are or will be breast-feeding while you are using this medicine, check with your doctor or pharmacist to discuss the risks to your baby.If you have diabetes, this medicine may affect your blood sugar. Check blood sugar levels closely and ask your doctor before adjusting the dose of your diabetes medicine.
Possible side effects
Side effects, that may go away during treatment, include dizziness or lightheadedness when sitting up or standing, or nausea. If they continue or are bothersome, check with your doctor. Check with your doctor as soon as possible if you experience diarrhea, muscle pain or cramps, vomiting, loss of appetite, restlessness, dry mouth, unusual thirst, unusual tiredness or weakness, or rapid or irregular heartbeat. If you notice other effects not listed above, contact your doctor, nurse, or pharmacist.
If you take too much
If overdose is suspected, contact your local poison control center or emergency room immediately. Symptoms of overdose may include dry mouth, dizziness, excessive urination followed by a decrease in amount of urine, muscle cramps, weakness, and weak or irregular heartbeat.
Additional information
Do not share this medicine with others for whom it was not prescribed. Do not use this medicine for other health conditions. Keep this medicine out of the reach of children. If using this medicine for an extended period of time, obtain refills before your supply runs out.
Drug interactions
Drug interactions can result in unwanted side effects or prevent a medicine from doing its job. Some medicines or medical conditions may interact with this medicine. Inform your doctor or pharmacist of all prescription and over-the-counter medicine that you are taking.