SORBITRATE
Clinical safety rating
cautionComprehensive clinical and safety monograph for SORBITRATE (SORBITRATE).
Sorbitrate (isosorbide dinitrate) is a nitrate that relaxes vascular smooth muscle by converting to nitric oxide (NO), which activates guanylate cyclase, increasing cGMP levels, leading to vasodilation. It primarily dilates coronary arteries and peripheral veins (venodilation > arteriodilation), reducing preload and afterload, thereby decreasing myocardial oxygen demand.
| Metabolism | Isosorbide dinitrate undergoes extensive first-pass metabolism in the liver via glutathione-dependent organic nitrate reductase (likely mediated by mitochondrial aldehyde dehydrogenase, ALDH2) to active metabolites isosorbide-2-mononitrate and isosorbide-5-mononitrate, with the latter being the major active metabolite. These metabolites are further glucuronidated and excreted renally. |
| Excretion | Renal: ~20% unchanged; remainder as metabolites (isosorbide-2-mononitrate, isosorbide-5-mononitrate). Biliary/fecal: negligible. |
| Half-life | Terminal elimination half-life: 5–6 hours. Clinical context: supports dosing every 6–8 hours; requires nitrate-free interval to prevent tolerance. |
| Protein binding | ~28% bound to albumin. |
| Volume of Distribution | Vd: 1.5–3.5 L/kg. Clinical meaning: extensive tissue distribution, high uptake in vascular smooth muscle. |
| Bioavailability | Sublingual: ~40–60% (bypasses first-pass metabolism). Oral: ~10–20% (extensive first-pass hepatic metabolism). |
| Onset of Action | Sublingual: 2–5 minutes; Oral: 15–40 minutes. |
| Duration of Action | Sublingual: 1–2 hours; Oral (immediate-release): 4–6 hours. Clinical notes: tolerance may develop with continuous exposure; sustained-release forms may last 8–12 hours. |
| Molecular Weight | 236.14 |
Sublingual: 2.5-5 mg as needed for acute angina, up to 10 mg per episode. Oral (sustained-release): 40-80 mg twice daily (immediate-release: 10-20 mg three times daily).
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required. GFR <10 mL/min: limited data, consider reduced dose. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: reduce dose by 50% or extend dosing interval. |
| Pediatric use | Not recommended for children <18 years due to lack of safety data. |
| Geriatric use | Start at lower end of dosing range (e.g., sublingual 2.5 mg, oral 10 mg twice daily) due to increased sensitivity and risk of hypotension. |
| 1st trimester | Limited human data; avoid use in first trimester unless clearly needed. Animal studies suggest risk. |
| 2nd trimester | Use only if clearly needed; no known teratogenicity but may cause fetal hypotension. |
| 3rd trimester | Use only if clearly needed; may cause fetal/neonatal hypotension and methemoglobinemia. |
Clinical note
Comprehensive clinical and safety monograph for SORBITRATE (SORBITRATE).
| Placental transfer | Isosorbide dinitrate and its metabolites cross the placenta in humans. |
| Breastfeeding | Excreted in breast milk in low amounts; unlikely to cause adverse effects in infant. Use caution with high doses or prolonged therapy. |
| Lactation Rating | L2 (Possibly Compatible) |
| Teratogenic Risk | Isosorbide dinitrate (Sorbitrate) has no well-controlled studies in pregnant women. Animal studies have not shown teratogenic effects. Due to vasodilatory effects, there is a potential risk of fetal hypoxia, especially during the second and third trimesters. Use only if clearly needed. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate for hypotension and reflex tachycardia. Monitor fetal heart rate for bradycardia or signs of distress. Assess for signs of maternal dizziness or syncope. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies have not shown impaired fertility. |
■ FDA Black Box Warning
No FDA boxed warning.
| Common Effects | Headache |
| Serious Effects |
Hypersensitivity to isosorbide dinitrate or nitratesConcomitant use with phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil)Severe anemiaIncreased intracranial pressure (e.g., head trauma, cerebral hemorrhage)Acute myocardial infarction with low filling pressureCardiac tamponade
| Precautions | Hypotension: May cause severe hypotension, especially upon standing (orthostatic hypotension). Correct hypovolemia before use., Tolerance: Continuous use may lead to development of tolerance; a daily nitrate-free interval (10-12 hours) is recommended to maintain efficacy., Headache: Common, often dose-limiting; may be severe initially but decreases with continued use., Worsening angina: Abrupt discontinuation may precipitate angina; taper gradually., Hypertrophic cardiomyopathy: Use with caution in patients with hypertrophic obstructive cardiomyopathy as vasodilation may worsen outflow obstruction., Increased intracranial pressure: Use with caution in patients with increased intracranial pressure (e.g., head trauma, cerebral hemorrhage). |
| Food/Dietary | No significant food interactions, but high-fat meals may delay absorption. Avoid excessive alcohol, which can cause additive vasodilation and hypotension. |
| Clinical Pearls | Sorbitrate (isosorbide dinitrate) is a nitrate vasodilator used for angina prophylaxis, not acute attacks. Sublingual form has faster onset; oral sustained-release provides longer duration. Tolerance develops rapidly with continuous dosing; use a 10-12 hour nitrate-free interval daily. Monitor for hypotension, especially with concurrent PDE-5 inhibitors (e.g., sildenafil) – absolute contraindication due to severe hypotension risk. Headache is common, often transient; advise analgesia. Avoid abrupt discontinuation. |
| Patient Advice | Take exactly as prescribed, do not stop abruptly. · For sublingual tablets: place under tongue and let dissolve; do not swallow. · Avoid alcohol as it can worsen dizziness and hypotension. · Prolonged use may lead to tolerance; a daily nitrate-free period is important. · Store tablets in original glass container away from heat and moisture. · Do not use within 24 hours of erectile dysfunction drugs like Viagra, Cialis, or Levitra. · Common side effects: headache, flushing, dizziness; contact doctor if severe or persistent. · If chest pain persists after one sublingual dose, call 911 immediately. |
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