Name of the Osmotic Diuretics Drugs
- Mannitol (Osmitrol)
- Isosorbide
1.Mannitol
| Mannitol (Osmitrol) |
| Availability Injection: 5%, 10%, 15%, 20%, 25% Solution: 5 g/100 ml |
| Indications and dosages ➣ Test dose for marked oliguria or suspected inadequate renal function Adults: 0.2 g/kg I.V. infusion (approximately 50 ml of 25% solution, 75 ml of 20% solution, or 100 ml of 15% solution) over 3 to 5 minutes. If urine flow doesn’t increase, second dose may be given; if response is inadequate after second dose, reevaluate patient. ➣ To prevent oliguria during cardiovascular and other surgeries Adults: 50 to 100 g I.V. infusion as 5% to 15% solution ➣ Acute oliguria Adults: Up to 100 g I.V. infusion as 15% to 25% solution Children: 0.25 to 2 g/kg I.V. or 60 mg/m2 as 15% to 20% solution over 2 to 6 hours ➣ To reduce intracranial pressure and brain mass Adults: 0.5 to 2 g/kg I.V. infusion as 15% to 25% solution given over 30 to 60 minutes Children: 1 to 2 g/kg I.V. or 30 to 60 g/m2 over 30 to 60 minutes. Small or debilitated patients may require smaller dose of 500 mg/kg. ➣ To reduce intraocular pressure Adults: 0.5 to 2 g/kg I.V. infusion as 15% to 25% solution given over 30 to 60 minutes. For preoperative use, give 60 to 90 minutes before surgery Children: 1 to 2 g/kg I.V. or 30 to 60 g/m2 over 30 to 60 minutes. Small or debilitated patients may require smaller dose of 500 mg/kg. ➣ To promote diuresis in drug toxicity Adults: 5% to 25% solution by I.V. infusion given continuously to maintain high urine output Children: 2 g/kg I.V. of 5% to 10% solution given continuously to maintain high urine output ➣ Irrigation during transurethral resection of prostate Adults: 2.5% to 5% solution instilled into bladder via indwelling urethral catheter, as needed |
Mechanism of Action
Elevates plasma osmolality, causing water to flow from tissues, such as brain and eyes, and from CSF, into extracellular fluid, thereby decreasing intracranial and intraocular pressure. As an osmotic diuretic, mannitol increases the osmolarity of glomerular filtrate, which decreases water reabsorption. This leads to increased excretion of water, sodium, chloride, and toxic substances. As an irrigant, mannitol minimizes the hemolytic effects of water used as an irrigant and reduces the movement of hemolyzed blood from the urethra to the systemic circulation, which prevents hemoglobinemia and serious renal complications.
Pharmacokinetics
- Metabolism: liver (very slight)
- Metabolites: glycogen
- Half-life: 100 min
- Excretion: urine (80%)
Administration
- Withhold drug until adequate renal function and urinary output are established.
- When administering for drug toxicity, give fluids and electrolytes to match fluid loss.
- Be aware that at low temperatures, solution may crystallize (especially concentrations above 15%). If crystals form, warm bottle in hot-water bath or dryheat oven or autoclave, then cool to body temperature or lower before giving.
- Don’t give electrolyte-free mannitol solutions with blood; when giving blood with mannitol, add 20 mEq or more of sodium chloride solution to each litre of mannitol solution to avoid pseudo agglutination.
- Know that drug may be given as continuous or intermittent I.V. infusion. Infuse at prescribed rate using infusion device and in-line filter. Give single I.V. dose over 30 to 90 minutes in adults. 2Avoid extravasation, because it may cause local edema and tissue necrosis.
Contraindications
- Active intracranial bleeding (except during craniotomy)
- Anuria secondary to severe renal disease
- Progressive heart failure, pulmonary congestion, renal damage, or renal dysfunction after mannitol therapy begins
- Severe pulmonary congestion or pulmonary edema
- Severe dehydration
Precautions:
- Severe renal disease, heart failure, mild to moderate dehydration
- Pregnant or breastfeeding patients.
Adverse reactions
- CNS: dizziness, headache, seizures
- CV: chest pain, hypotension, hypertension, tachycardia, thrombophlebitis, heart failure, vascular overload
- EENT: blurred vision, rhinitis
- GI: nausea, vomiting, diarrhea, dry mouth
- GU: polyuria, urinary retention, osmotic nephrosis
- Metabolic: dehydration, water intoxication, hypernatremia, hyponatremia, hypovolemia, hypokalemia, hyperkalemia, metabolic acidosis
- Respiratory: pulmonary congestion
- Skin: rash, urticaria
- Other: chills, fever, thirst, edema, extravasation with edema and tissue necrosis
Patient monitoring
- Monitor I.V. site carefully to avoid extravasation and tissue necrosis.
- In comatose patient, insert indwelling urinary catheter as ordered to monitor urine output.
- Monitor renal function tests, urinary output, fluid balance, central venous pressure, and electrolyte levels (especially sodium and potassium).
- Watch for excessive fluid loss and signs and symptoms of hypovolemia and dehydration.
- Assess for evidence of circulatory overload, including pulmonary edema, water intoxication, and heart failure
Patient teaching
- Teach patient about importance of monitoring exact urinary output.
- Advise patient to report pain at infusion site as well as adverse reactions, such as increased shortness of breath or pain in back, legs, or chest.
- Tell patient drug may cause thirst or dry mouth. Emphasize that fluid restrictions are necessary, but that frequent mouth care should ease these symptoms.
- As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.
Nursing Considerations
- If crystals form in mannitol solution exposed to low temperature, place solution in hot-water bath to redissolve crystals.
- Use a 5-micron in-line filter when administering drug solution of 15% or greater.
- During I.V. infusion of mannitol, monitor vital signs, central venous pressure, and fluid intake and output every hour. Measure urine output with indwelling urinary catheter, as appropriate.
- Check weight and monitor BUN and serum creatinine electrolyte levels daily.
- Provide frequent mouth care to relieve thirst and dry mouth.
2.Isosorbide
| Availability isosorbide dinitrate Capsules: 40 mg Capsules (extended-release): 40 mg Tablets: 2.5 mg, 5 mg, 10 mg, 20 mg, 30 mg, 40 mg Tablets (chewable): 5 mg, 10 mg Tablets (extended-release): 20 mg, 40 mg Tablets (sublingual): 2.5 mg, 5 mg, 10 mg isosorbide mononitrate Tablets: 10 mg, 20 mg Tablets (extended-release): 30 mg, 60 mg, 120 mg |
| Indications and dosages ➣ Treatment and prophylaxis in situations likely to provoke acute angina pectoris Adults: 2.5 to 5 mg S.L. May repeat dose q 5 to 10 minutes for a total of three doses in 15 to 30 minutes ➣ Prophylaxis of angina pectoris Adults: 5 to 40 mg P.O. (dinitrate conventional tablets) two to three times daily. Or 5 to 20 mg (mononitrate conventional tablets) b.i.d. Or 30 to 60 mg (mononitrate extended-release tablets) once daily. After several days, dosage may be increased to 120 mg (given as single 120-mg tablet or two 60-mg tablets) once daily. Rarely, 240 mg/day (mononitrate extended-release tablets) may be needed |
Mechanism of Action
Isosorbide may interact with nitrate receptors in vascular smooth-muscle cell membranes. By interacting with receptors’ sulfhydryl groups, drug is reduced to nitric oxide. Nitric oxide activates the enzyme guanylate cyclase, increasing intracellular formation of cyclic guanosine monophosphate (cGMP). An increased cGMP level may relax vascular smooth muscle by forcing calcium out of muscle cells, causing vasodilation. This improves cardiac output by reducing mainly preload but also afterload
Pharmacokinetics
- Bioavailability: Immediate release, 40-50%
- Extensively metabolized in liver to conjugated metabolites
- Half-life: 1 hr
- Excretion: Urine (80-100%), feces
Administration
- Give oral form 30 minutes before or 1 to 2 hours after a meal. Make sure patient swallows tablets or capsules whole.
- Have patient wet S.L. tablet with saliva before placing it under tongue. To avoid tingling sensation, have him place tablet in buccal pouch
Contraindications
- Hypersensitivity to drug
- Severe anemia
- Acute myocardial infarction
- Angle-closure glaucoma
- Concurrent sildenafil therapy
Precautions:
- Head trauma, volume depletion
- Elderly patients
- pregnant or breastfeeding patients
- Children
Adverse reactions
- CNS: dizziness, headache, apprehension, asthenia, syncope
- CV: orthostatic hypotension, tachycardia, paradoxical bradycardia, rebound hypertension
- EENT: sublingual burning (with S.L. route)
- GI: nausea, vomiting, dry mouth, abdominal pain
- Skin: flushing
Patient monitoring
- Monitor ECG and vital signs closely, especially blood pressure.
- In suspected overdose, assess for signs and symptoms of increased intracranial pressure.
- Monitor arterial blood gas values and methemoglobin levels.
Patient teaching
- Teach patient to take oral drug 30 minutes before or 1 to 2 hours after a meal.
- Inform patient that drug may cause headache. Advise him to treat headache as usual and not to alter drug schedule. If headache persists, tell him to contact prescriber.
- Instruct patient to move slowly when sitting up or standing, to avoid dizziness or light-headedness from sudden blood pressure decrease.
- As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs and tests mentioned above.
Nursing Considerations
- Use isosorbide cautiously in patients with hypovolemia or mild hypotension. Monitor patient for increased hypotension and reduced cardiac output.
- Give drug 1 hour before or 2 hours after meals. Give with meals if patient experiences severe headaches or adverse GI reactions.
- Know that patient may experience daily headaches from isosorbide’s vasodilating effects. Give acetaminophen, as prescribed, to relieve pain.
- Monitor blood pressure often during isosorbide therapy, especially in elderly patients; drug may cause severe hypotension.
- Keep isosorbide protected from heat and light.
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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