Sorbitrate protocol and dosing
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Sorbitrate isosorbide dinitrate dosing protocol angina
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Here is a complete reference for Sorbitrate (Isosorbide Dinitrate - ISDN) dosing and protocols:
Sorbitrate (Isosorbide Dinitrate) - Protocol & Dosing
Sorbitrate is a brand name for isosorbide dinitrate (ISDN), an organic nitrate vasodilator available as 5 mg, 10 mg, 20 mg, 30 mg, and 40 mg tablets.
Mechanism of Action
ISDN releases nitric oxide (NO) - NO activates guanylyl cyclase - increases cGMP - relaxes vascular smooth muscle. This produces:
- Venodilation (reduces preload) - primary effect at low doses
- Arterial dilation (reduces afterload) - at higher doses
- Coronary vasodilation - relieves coronary spasm
Indications
- Angina pectoris (stable, unstable, variant/Prinzmetal)
- Heart failure (with hydralazine, especially in African Americans with HFrEF)
- Acute MI (adjunct)
Dosing by Formulation
1. Sublingual Tablets (2.5 mg, 5 mg)
| Indication | Dose | Frequency |
|---|---|---|
| Acute angina relief | 2.5-5 mg SL | May repeat every 5-10 min; max 3 doses in 15-30 min |
| Pre-activity prophylaxis | 2.5-5 mg SL | 15 min before anticipated exertion |
| Chronic prophylaxis | 2.5-10 mg SL | Every 2 hours |
- Onset: 2-5 minutes | Duration: 1-2 hours
- Starting dose: Do not exceed 5 mg initially (risk of severe hypotension)
2. Immediate-Release Oral Tablets (5, 10, 20, 30, 40 mg)
| Purpose | Initial Dose | Maintenance Dose | Max |
|---|---|---|---|
| Angina prophylaxis | 5-20 mg PO | 10-40 mg PO | 480 mg/day |
| Heart failure | 20-40 mg PO TID | Up to 40 mg TID | - |
- Frequency: 2-3 times daily (eccentric dosing - see Tolerance section below)
- Typical schedule: 0700 h and 1200 h (bid) or 0700, 1200, 1700 h (tid)
- Onset: 15-40 minutes | Duration: 4-6 hours
3. Extended-Release / Sustained-Release (40 mg tablets/capsules)
| Initial | Maintenance | Max |
|---|---|---|
| 40 mg PO | 40-80 mg PO | 160 mg/day |
- Frequency: Twice daily
- Duration of action: 8-10 hours
- Caution: Avoid in acute MI or acute HF (adverse effects not easily reversible)
4. Chewable Tablets
- Dose: 5-10 mg every 2-4 hours
- Duration: 2-3 hours
5. IV Isosorbide Dinitrate (for severe/rest angina)
- Reserved for severe, recurrent rest angina
- Onset is rapid (minutes); effects reverse quickly when infusion stopped
Tolerance Protocol - CRITICAL
Nitrate tolerance develops rapidly with continuous use. This is the most important clinical consideration.
Rule: Always provide a nitrate-free interval of 10-14 hours (usually overnight).
| Formulation | Recommended Schedule | Nitrate-Free Window |
|---|---|---|
| IR tablets (bid) | 0700 and 1200 | 1200 to 0700 (19 hrs) |
| IR tablets (tid) | 0700, 1200, 1700 | 1700 to 0700 (14 hrs) |
| Extended-release | Interval must be >18 hrs (exact schedule unclear) | Possibly not achievable |
Note: Large controlled trials confirm that no ISDN dosing regimen provides more than ~12 hours of continuous anti-anginal efficacy per day. Extended-release products on an eccentric schedule (e.g., 0800 & 1400) were no better than placebo after 4 weeks - Katzung's Basic and Clinical Pharmacology, 16th Ed.
Heart Failure Use (Hydralazine + ISDN)
Used when ACE inhibitors/ARBs are not tolerated, or as add-on in African Americans with HFrEF.
| Drug | Dose |
|---|---|
| Isosorbide dinitrate | 20-40 mg PO TID or QID |
| Hydralazine | 25-75 mg PO TID or QID |
| Fixed combination (BiDil) | 1-2 tablets TID (each tablet = hydralazine 37.5 mg + ISDN 20 mg) |
Shown to reduce mortality, HF hospitalizations, and improve quality of life - Goldman-Cecil Medicine.
Key Precautions
| Situation | Guidance |
|---|---|
| Absolute CI: PDE-5 inhibitors (sildenafil, tadalafil) | Severe hypotension, potentially fatal |
| Absolute CI: Riociguat | Same mechanism - profound hypotension |
| Hypotension (SBP <90 mmHg) | Avoid or use with extreme caution |
| Volume depletion | Risk of severe orthostatic hypotension |
| Hypertrophic cardiomyopathy | Can worsen obstruction and angina |
| Headache | Very common (vasodilation); treat with paracetamol/aspirin - usually resolves with continued use |
| Paradoxical bradycardia | Can occur with nitrate-induced hypotension |
Onset & Duration Summary
| Form | Onset | Duration |
|---|---|---|
| SL tablet | 2-5 min | 1-2 hours |
| Oral IR tablet | 15-40 min | 4-6 hours |
| Chewable tablet | ~5 min | 2-3 hours |
| Oral ER tablet | 30-60 min | 8-10 hours |
Source: Katzung's Basic and Clinical Pharmacology 16th Ed, Table 12-3; Lippincott Illustrated Reviews: Pharmacology; Goldman-Cecil Medicine; Medscape Drug Reference
Bottom line: Start low (5 mg), always use eccentric/asymmetric dosing with a nitrate-free interval to prevent tolerance, and absolutely avoid co-administration with PDE-5 inhibitors.
NTG inj
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nitroglycerin injection IV infusion protocol dosing mcg/min titration
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Here is the complete IV Nitroglycerin (NTG) injection protocol:
IV Nitroglycerin (NTG) Injection - Protocol & Dosing
Generic: Nitroglycerin | Also known as: Glyceryl trinitrate (GTN) IV | Tridil, Nitro-Bid IV
Indications for IV NTG
- Unstable angina / NSTE-ACS refractory to sublingual NTG
- Acute MI with ongoing ischemia or heart failure
- Acute decompensated heart failure (reduces preload/afterload)
- Hypertensive emergency (especially with ACS or pulmonary edema)
- Perioperative hypertension control
- Induction of controlled hypotension (intraoperatively)
Preparation & Dilution
NOT for direct IV injection - MUST be diluted first
| Concentration | Preparation |
|---|---|
| Standard (most common): 50 mcg/mL | 50 mg in 250 mL D5W or 0.9% NaCl |
| Double concentration: 100 mcg/mL | 50 mg in 500 mL D5W or NS |
| 200 mcg/mL | 50 mg in 250 mL (ICU concentrated) |
Critical preparation notes:
- Use glass IV bottles only - NTG is absorbed by many plastics
- Use non-PVC (polyethylene) tubing - PVC tubing absorbs NTG significantly
- Do NOT mix with other drugs in the same line
- Protect from light during infusion
- Prepare fresh every 24 hours
Dosing Protocol
Step 1 - Before Starting IV NTG
Give sublingual NTG 0.3-0.6 mg (spray or tablet); repeat every 5 min x 3 doses. If symptoms persist after 3 SL doses, start IV infusion. - Harrison's Principles of Internal Medicine, 22nd Ed
Step 2 - Initial Infusion
| Indication | Starting Dose |
|---|---|
| Angina / ACS | 5-10 mcg/min |
| Hypertensive emergency | 10-20 mcg/min |
| CHF/acute HF | 0.25-0.5 mcg/kg/min (or 10-20 mcg/min) |
| Perioperative HTN | 5-10 mcg/min |
Step 3 - Titration
| Phase | Action |
|---|---|
| No response (doses up to 20 mcg/min) | Increase by 5 mcg/min every 3-5 min |
| No response at 20 mcg/min | Increase by 10 mcg/min every 3-5 min |
| Still no response | May increase by 20 mcg/min every 3-5 min |
| Partial response seen | Reduce increment size; lengthen interval between dose increases |
Step 4 - Infusion Rate Quick Reference (50 mg/250 mL = 200 mcg/mL)
| Dose (mcg/min) | Rate (mL/hr) |
|---|---|
| 5 | 1.5 |
| 10 | 3 |
| 20 | 6 |
| 40 | 12 |
| 60 | 18 |
| 80 | 24 |
| 100 | 30 |
| 200 | 60 |
(For 50 mg/250 mL concentration: mL/hr = mcg/min × 0.3)
Dose Ranges by Indication
| Indication | Typical Range | Max |
|---|---|---|
| Angina / ACS | 5-200 mcg/min | 200 mcg/min |
| Hypertensive emergency | 5-400 mcg/min | 400 mcg/min (provider only) |
| Perioperative HTN | 5-100 mcg/min | 200 mcg/min |
| Acute HF | 10-200 mcg/min | 200 mcg/min |
| Pediatric (off-label) | 0.25-0.5 mcg/kg/min, titrate up | 5 mcg/kg/min |
Titration Endpoints (Stop or Reduce)
- SBP drops to <90 mmHg (absolute stop point)
- SBP drop of >10 mmHg from baseline (reassess)
- Heart rate increases significantly
- Chest pain/ischemia relieved
- Adequate reduction in SVR or PCWP (in hemodynamic monitoring)
- Headache, nausea, or symptomatic hypotension
Pharmacokinetics of IV NTG
| Parameter | Value |
|---|---|
| Onset | 1-2 minutes |
| Peak effect | 3-5 minutes |
| Duration | 3-5 min after stopping infusion |
| Half-life | ~1-4 minutes |
| Metabolism | Rapid hepatic; to dinitrates & mononitrates |
Key property: Effect reverses within minutes of stopping infusion - makes it very titratable.
Hemodynamic Effects by Dose
| Dose | Primary Effect |
|---|---|
| Low (<30 mcg/min) | Venodilation - reduces preload (PCWP falls) |
| Moderate (30-100 mcg/min) | Coronary vasodilation, mild afterload reduction |
| High (>100 mcg/min) | Arterial dilation - reduces afterload (SVR falls) |
At lower dosages, the primary effect is on preload; at higher infusion rates, afterload is reduced. NTG also dilates epicardial coronary vessels and collaterals. - Brenner & Rector's The Kidney
Transitioning Off IV NTG
- Once pain-free for 12-24 hours, transition to topical or oral nitrates
- Taper gradually (do not abrupt-stop after prolonged infusion) to avoid rebound ischemia
- Remove all topical nitrate patches before starting IV NTG
Contraindications
| Absolute | Relative |
|---|---|
| PDE-5 inhibitors (sildenafil/vardenafil within 24 h; tadalafil within 48 h) | Volume depletion |
| Hypotension (SBP <90 mmHg) | Right ventricular infarction |
| Raised ICP / severe head trauma | Hypertrophic obstructive cardiomyopathy |
| Severe aortic stenosis |
Tolerance
- Uninterrupted infusion >24 hours produces tolerance
- Allow a nitrate-free interval if transitioning to long-term oral nitrate therapy
- Tolerance does not typically matter clinically during acute short-term IV use
Key Monitoring
- Continuous BP monitoring (arterial line preferred in ICU/hemodynamic instability)
- Continuous ECG monitoring
- Heart rate
- Urine output
- PCWP / CVP (if Swan-Ganz catheter in place)
- Symptoms of headache, dizziness, nausea
Sources: Harrison's Principles of Internal Medicine 22nd Ed; Brenner & Rector's The Kidney; Medscape Drug Reference; Adult Critical Care IV Titration Protocols
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