Loading dosage in status epilepticus
INDICATIONS
- Status epilepticus for patients not taking maintenance phenytoin
- if on maintenance phenytoin, contact neurology SpR to discuss reduced dose of IV phenytoin or use of levetiracetam. See Levetiracetam IV guideline
PREPARATIONS
- Phenytoin sodium injection 50 mg/mL in 5 mL (250 mg) ampoules
DILUENTS
- Sodium chloride 0.9% only
ADMINISTRATION
- Administer slowly into a large vein
- if phenytoin is given too rapidly, hypotension, cardiac arrhythmias, impaired cardiac conduction, CNS depression or respiratory arrest can occur
Check infusion site regularly
- Soft tissue irritation and inflammation can occur with/without extravasation
- varies from slight tenderness to extensive necrosis and sloughing, requiring amputation in rare instances
- Ensure extravasation does not occur
Monitor ECG and BP
- Monitor all patients with continuous ECG and BP throughout the infusion
DOSAGE
- Phenytoin 20 mg/kg up to a maximum of 2 g by slow IV administration into a large vein through an in-line filter (0.22-0.5 micron) no faster than 50 mg/min
IV infusion of undiluted phenytoin (50 mg/mL) via syringe pump
- Preferred method of delivery at dose of 20mg/kg
Table 1: Administration of undiluted phenytoin sodium 50 mg/mL via syringe pump at dose of 20 mg/kg
| Weight (kg) | 45 | 50 | 55 | 60 | 65 | 70 | 75 | 80 | 85 | 90 | 95 | 100 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dose (mg) | 900 | 1000 | 1100 | 1200 | 1300 | 1400 | 1500 | 1600 | 1700 | 1800 | 1900 | 2000 |
| Volume to be drawn up (mL) | 18 | 20 | 22 | 24 | 26 | 28 | 30 | 32 | 34 | 36 | 38 | 40 |
| Syringe pump rate (mL/hr) | 36 | 40 | 44 | 48 | 52 | 56 | 60 | 60 | 60 | 60 | 60 | 60 |
How to give
- Use a 0.22-0.50 micron in-line filter. Obtain from supplies department
- Draw up required volume of phenytoin sodium injection 50 mg/mL in syringe used by syringe pump
- need more than one ampoule of phenytoin sodium injection 50 mg/mL in 5 mL (250 mg)
- Before phenytoin administration, flush cannula with sodium chloride 0.9%
- Administer over at least 30 min via syringe pump set at required rate
- After phenytoin administration, flush cannula with sodium chloride 0.9%
IV infusion of diluted phenytoin
- Use if a syringe pump is not available
- Phenytoin sodium injection can be diluted in 100 mL sodium chloride 0.9% to a maximum concentration of 10 mg/mL (i.e. max 1000 mg in 100 mL)
- if dose exceeds 1000 mg, divide total dose between 2 x 100 mL bags and run concurrently
Table 2: Administration of diluted phenytoin sodium by IV infusion at dose of 20 mg/kg
| Weight (kg) | Total dose phenytoin (mg) required | Total volume (mL) of phenytoin concentrate (50 mg/mL) | Bag A Dose (volume) of phenytoin concentrate (50 mg/mL) to be added to 100 mL bag sodium chloride 0.9% |
Bag B Dose (volume) of phenytoin concentrate (50 mg/mL) to be added to 100 mL bag sodium chloride 0.9% |
|---|---|---|---|---|
| Run bag A at 150 mL/hr | ||||
| When bag A and bag B both required, run together at the same time via the same cannula, each at 150 mL/hr | ||||
| 45 | 900 | 18 | 900 mg (18 mL) |
Bag B not required as dose ≤1000 mg |
| 50 | 1000 | 20 | 1000 mg (20 mL) |
|
| 55 | 1100 | 22 | 500 mg (10 mL) |
600 mg (12 mL) |
| 60 | 1200 | 24 | 500 mg (10 mL) |
700 mg (14 mL) |
| 65 | 1300 | 26 | 500 mg (10 mL) |
800 mg (16 mL) |
| 70 | 1400 | 28 | 500 mg (10 mL) |
900 mg (18 mL) |
| 75 | 1500 | 30 | 1000 mg (20 mL) |
500 mg (10 mL) |
| 80 | 1600 | 32 | 1000 mg (20 mL) |
600 mg (12 mL) |
| 85 | 1700 | 34 | 1000 mg (20 mL) |
700 mg (14 mL) |
| 90 | 1800 | 36 | 1000 mg (20 mL) |
800 mg (16 mL) |
| 95 | 1900 | 30 | 1000 mg (20 mL) |
900 mg (18 mL) |
| 100 | 2000 | 40 | 1000 mg (20 mL) |
1000 mg (20 mL) |
How to give
- Check that solution is free of haziness or precipitation
- Use a 0.22-0.50 micron in-line filter. Obtain from supplies department
- Before phenytoin administration, flush cannula with sodium chloride 0.9%
- Start administration immediately after dilution to ensure infusion is completed within 1 hr of preparation
- Follow selected infusion rates to ensure not administered faster than 50 mg/min
- After phenytoin administration, flush cannula with sodium chloride 0.9%
MONITORING
- In patients given an IV loading dose, measure phenytoin concentration within 2-3 days of initiating therapy
- obtain a second phenytoin concentration in another 3-5 days
- Adjust subsequent doses of phenytoin
- If the plasma phenytoin concentrations have not changed over a 3-5 day period, the monitoring interval can usually be increased to once weekly in the acute clinical setting
Date updated: 2024-01-08