Dr Sharon Rees @reesprescribe
Day 1: Discovered in the late 1950s, the loop diuretic #furosemide's chemical origins are traced back to sulfonamide derivatives. Despite not retaining the allergenic aromatic amine group, the product info still advises against taking if the patient has a history of sulfa-allergy.
Dr Sharon Rees @reesprescribe
Day 2: #furosemide remains in widespread use, mainly to manage oedema (pulmonary, heart failure and resistant oedema). Oral dose 40-120 mg/day (spans all indications), intramuscular (IM)/Intravenous (IV) titrated from 20-50 mg initially to max 1.5 g/day.
Dr Sharon Rees @reesprescribe
Day 2 (cont): IV diuresis starts within 10 minutes, oral within 1 hour, with a duration approximately 4-6 hrs. To preserve potassium (K+), can be combined with other diuretics (amiloride, triamterene, spironolactone) or K+.
Dr Sharon Rees @reesprescribe
Day 3: MOA; the Na-K-2Cl major transport proteins mediate salt absorption throughout nephron, especially in the loop of Henle. Competition from #furosemide inhibits reabsorption, causing increased water excretion (plus many electrolytes). Also vasodilatory action, enhancing treatment of acute pulmonary oedema.
Dr Sharon Rees @reesprescribe
Day 4: Kinetics; oral bioavailability variable (severe oedema will also reduce gastrointestinal absorption), low Vd and the drug is taken to tubules as highly protein bound. Hepatic metabolism produces one active metabolite, t ½ 2-4 hours (increased in severe renal failure). Half cleared renally (unchanged) and rest metabolised in kidneys.
Dr Sharon Rees @reesprescribe
Day 5: Common ADRs #furosemide include dizziness, headaches, electrolyte disturbances, dehydration, nephrocalcinosis (infants); Rare; blood disorders, tinnitus, gout, vasculitis (not exhaustive). Overdose delirium, cardiac toxicity, excessive diuresis/shock, acute renal failure.
Dr Sharon Rees @reesprescribe
Day 5 (cont): #furosemide can cause dose-dependent hearing loss; unlikely to be permanent if no risk factors, such as an increased drug concentration re hepatic failure. Cochlear hair cells need correct K+/Na+ balance. Competition for the Na+/K+ transporter may disrupt function or affect cochlear blood flow.
Dr Sharon Rees @reesprescribe
Day 6: #furosemide drug-drug interactions; all anti-hypertensives, anti-psychotics (cardio toxicity), associated with K+ loss, increased risk digoxin toxicity, any drug causing hypokalaemia or a prolonged QT interval, increased lithium excretion, risk nephron toxicity with non-steroidal anti-inflammatory drugs, increased ototoxicity risk if used with aminoglycosides and vanc (not exhaustive).
Dr Sharon Rees @reesprescribe
Day 6 (cont): Drug-food interaction #furosemide; excessive liquorice intake increases risk of hypokalaemia! A lot needs to be taken, but the active ingredient causes increased mineralocorticoid levels, so there is more potassium excretion.
Dr Sharon Rees @reesprescribe
Day 7: Long-term treatment with #furosemide can lead to resistance. Possible mechanisms are progressively reduced renal function, altered kinetics so less drug delivery to tubules and adaptive increased salt re-absorption downstream. Dietary salt restriction is important if there is resistance.
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Complete the additional reading suggested below and then answer the ten questions. Please submit the answers to reesprescribe@gmail.com as a numbered list with TRUE/FALSE or the correct A,B,C,D option. If you achieve 8 or more out of 10 on the questions, a CPD certificate will be emailed to you.
Further reading on #furosemide
- Furosemide Tablets BP 20 mg: https://www.medicines.org.uk/emc/product/5861/smpc
- Furosemide is a first-line drug for hypertension TRUE or FALSE?
- Which is TRUE?
- Oral furosemide starts to work in five minutes
- Furosemide only works in the kidney
- Furosemide is helpful to manage heart failure-related oedema
- Everyone on furosemide needs plasma drug level monitoring
- Hyperkalaemia is the main electrolyte issue with using furosemide TRUE or FALSE?
- Furosemide has a severe drug interaction with
- Foods high in potassium
- Risperidone
- Salbutamol
- Phenytoin
- The drug target for furosemide is
- A membrane transport protein in the thick ascending loop of Henle, which moves sodium, potassium and chlorine ions across the cell membrane
- A calcium ion channel in the distal convoluted tubule
- An antiport exchanging sodium ions and water for chloride found in the descending loop of Henle
- Water-filled pores along the nephron length
- Which is TRUE?
- Furosemide cannot be combined with other diuretics
- Furosemide has an active metabolite
- Furosemide is extensively metabolised in the liver
- The half-life of furosemide is several days
- Ototoxicity is likely to result in permanent deafness TRUE or FALSE?
- If there is diuretic resistance, it is important to follow a low sodium diet TRUE or FALSE?
- A lower dose of furosemide should be considered in the elderly because they are susceptible to side effects TRUE or FALSE?
- Which of the following is NOT a common side effect for furosemide?
- Increased blood creatinine levels
- Muscle spasm
- Headache
- Gout