ISMOTIC
Clinical safety rating
cautionComprehensive clinical and safety monograph for ISMOTIC (ISMOTIC).
Isosmotic solution of mannitol; increases plasma osmolality, drawing water from tissues into the vasculature and reducing intracranial/intraocular pressure via osmotic diuresis.
| Metabolism | Not significantly metabolized; primarily excreted unchanged by the kidneys. |
| Excretion | Renal: 90-95% unchanged; biliary/fecal: <5% |
| Half-life | 4.5-6.0 hours in adults with normal renal function; prolonged in renal impairment (up to 24-48 hours in anuria) |
| Protein binding | <10% (negligible), primarily albumin |
| Volume of Distribution | 0.5-0.7 L/kg; limited to extracellular fluid compartment |
| Bioavailability | Oral: 60-70% (first-pass metabolism); Intravenous: 100% |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 5-15 minutes |
| Duration of Action | Oral: 4-6 hours; Intravenous: 2-4 hours; clinical effect correlates with serum osmolarity increase |
| Molecular Weight | 191.2 |
1-2 g orally every 6-8 hours, maximum 8 g/day; or 1-2 g intravenously over 5-10 minutes every 6-8 hours, maximum 8 g/day.
| Dosage form | SOLUTION |
| Renal impairment | GFR >50 mL/min: no adjustment; GFR 10-50 mL/min: administer every 12 hours; GFR <10 mL/min: administer every 24 hours. |
| Liver impairment | No adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Avoid in severe hepatic impairment (Child-Pugh C) due to risk of hepatic encephalopathy. |
| Pediatric use | 25-50 mg/kg orally every 6-8 hours, maximum 2 g/dose; or 25-50 mg/kg intravenously over 5-10 minutes every 6-8 hours, maximum 2 g/dose. |
| Geriatric use | Initiate at low end of dosing range (1 g every 8 hours) due to age-related renal function decline; adjust based on creatinine clearance. |
| 1st trimester | Ismotic (isosorbide) is an osmotic diuretic. Data in first trimester are lacking; theoretical risk of teratogenicity due to maternal hypotension and reduced uterine blood flow. Use only if clearly needed. |
| 2nd trimester | Similar to t1; monitor maternal blood pressure and electrolytes. Animal studies show no consistent teratogenicity, but human data limited. |
| 3rd trimester | May cause maternal hypovolemia and oligohydramnios; avoid near term. Use only if benefit outweighs risk, with fetal monitoring. |
Clinical note
Comprehensive clinical and safety monograph for ISMOTIC (ISMOTIC).
| Placental transfer | Crosses placenta based on low molecular weight (191.2 Da) and similar compounds. Direct evidence in humans limited. |
| Breastfeeding | Not known if excreted in human milk. Because of low molecular weight, excretion is possible. Caution advised; consider alternatives. |
| Lactation Rating | L3 (Moderately Safe) - limited data, but short half-life and low oral bioavailability suggest low risk if used short-term. |
| Teratogenic Risk | No adequate and well-controlled studies in pregnant women. In animal studies, administration of isosorbide dinitrate (active ingredient of Ismotic) during organogenesis produced fetal toxicity at doses 35 times the maximum human dose. First trimester: unknown risk, avoid unless clearly needed. Second and third trimesters: risk of maternal hypotension and reduced placental perfusion; use only if potential benefit justifies risk. Should be used with caution near term due to risk of neonatal hypotension. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate frequently, especially during initiation and dose titration. Assess fetal heart rate patterns if used near term. Monitor for signs of hypotension (dizziness, syncope) and reflex tachycardia. Assess maternal fluid status. Consider placental insufficiency if prolonged use. |
| Fertility Effects | No specific data on fertility effects in humans. In animal studies, no adverse effects on fertility were observed at clinically relevant doses. Theoretical risk of altered hemodynamics affecting reproductive function, but not established. |
■ FDA Black Box Warning
None.
| Serious Effects |
AnuriaSevere dehydrationHypovolemiaHypersensitivity to isosorbideIntracranial bleeding (except during surgery)
| Precautions | Monitor renal function and serum electrolytes, Avoid in patients with anuria or severe renal impairment, Risk of pulmonary edema, heart failure, and electrolyte disturbances |
| Food/Dietary | Avoid high-tyramine foods (aged cheeses, cured meats, soy products) as hydralazine may increase tyramine sensitivity? No significant specific food interactions for isosorbide dinitrate/hydralazine. However, limit high-salt foods to manage heart failure. Avoid alcohol due to additive hypotensive effects. |
| Clinical Pearls | ISOMOTIC (isosorbide dinitrate/hydralazine) is a fixed-dose combination for heart failure in self-identified Black patients. Monitor for hypotension, headache, and dizziness. Avoid use with PDE-5 inhibitors (e.g., sildenafil) due to risk of severe hypotension. Titrate gradually to target dose to minimize adverse effects. May cause drug-induced lupus-like syndrome or peripheral neuropathy with hydralazine; consider slow acetylator phenotype risk. |
| Patient Advice | Take this medication exactly as prescribed to control your heart failure symptoms. · Do not take erectile dysfunction medicines (like sildenafil, tadalafil) while on this drug, as it can cause a dangerous drop in blood pressure. · You may experience headaches, dizziness, or lightheadedness when starting; these often improve over time. If severe, contact your doctor. · Avoid alcohol, which can worsen dizziness and low blood pressure. · Report any unexplained joint pain, fever, rash, or numbness/tingling in your hands or feet to your doctor immediately. · Swallow tablets whole; do not crush or chew. · Do not stop suddenly without consulting your doctor; abrupt discontinuation can worsen heart failure. |
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