Adult oral dose (immediate-release)

• Katzung says adult dosing can begin at 500 or 1000 mg/day. - Katzung's Basic and Clinical Pharmacology, 16th Ed.
• Kaplan & Sadock's gives adjunctive epilepsy dosing as 500 to 1000 mg/day, raised every 2 weeks by 1000 mg/day, up to 3000 mg/day. - Kaplan & Sadock's Comprehensive Textbook of Psychiatry
• Tablets come as 250, 500, 750 and 1000 mg. There is also a 100 mg/mL oral solution and a 500 or 750 mg extended-release tablet. The extended-release form is given once daily, starting at 1000 mg in patients 12 years or older.
• Absorption is excellent, and IV doses match oral doses when the oral route isn't possible. - The Harriet Lane Handbook, 23rd Ed.

Children

• 1 month to under 6 months: 7 mg/kg twice daily, titrated to a maximum of 21 mg/kg twice daily.
• 6 months to under 4 years: 10 mg/kg twice daily, titrated to a maximum of 25 mg/kg twice daily.
• 4 to under 16 years: 10 mg/kg twice daily, titrated to a maximum of 30 mg/kg twice daily.

Renal adjustment (adults and adolescents weighing 50 kg or more)

Other points

• Liver impairment needs no dose adjustment.
• Elderly patients need care in choosing the dose, and their renal function should be monitored.
• Don't stop it abruptly. Taper the dose.
• The most common side effects are somnolence, asthenia, ataxia and dizziness. Behavioral and mood changes are less common but serious. - Goodman & Gilman's, Toxicity

Recent evidence

• Augmented renal clearance in critically ill patients may mean standard doses are too low (PMID 41688794, 2026).
• Drug-level monitoring in pregnancy (PMID 41120802, 2026).

What a "Paeds" (or "Neonatal") selection usually changes

• Tidal volume range: the settable range drops to small volumes, often a few mL up to a few hundred mL. The adult range may be locked out.
• Weight or height entry: the machine uses it to calculate predicted body weight and suggest starting settings.
• Default respiratory rate: it starts higher.
• Trigger sensitivity: it uses a flow trigger instead of a pressure trigger, with a more sensitive setting.
• Flow and inspiratory time: the flow range and inspiratory time are scaled down.
• Pressure limits: the maximum pressure limit and its alarm are lower.
• Alarm defaults: the high and low tidal volume, minute volume, and rate alarms are narrower and sit at pediatric levels.
• Circuit and leak compensation: the circuit compliance test and the leak (uncuffed tube) compensation are adjusted for small-volume breaths.
• Anesthesia machines: a different circuit or absorber setup may be needed.

Why those changes are needed (from the textbooks)

• Tidal volume: start at 6 to 8 mL/kg of predicted body weight, based on length, age and sex. - Mulholland and Greenfield's Surgery, 7e, p. 5305
• Respiratory rate: minute ventilation is higher than in adults, so younger children need rates of 15 to 30 breaths/min, titrated to CO2 clearance. - Mulholland and Greenfield's Surgery, 7e, p. 5305
• Dead space: the ventilator tubing's dead space far exceeds a young child's tidal volume. Inline flow sensors at the endotracheal tube therefore measure the true delivered volume more precisely. - Mulholland and Greenfield's Surgery, 7e, p. 5305
• Pressures: lung compliance varies widely by age and disease. Initial pressures are estimated by hand-bagging with a manometer and watching chest rise. - Mulholland and Greenfield's Surgery, 7e, p. 5305
• Airway resistance: it rises with the fourth power of airway radius, so a small amount of edema or mucus causes a large rise in resistance. This is why pressure and expiratory time matter more in children. - Mulholland and Greenfield's Surgery, 7e, p. 5305
• Neonates:
  • The lung is fragile and easily injured by large tidal volumes.
  • PEEP should be used, and even brief circuit disconnection can collapse alveoli.
  • Conventional anesthesia-machine ventilators may not be suitable for premature or low-birthweight infants. A neonatal ventilator that measures small volumes and pressures accurately is preferable. - Miller's Anesthesia, 10e, p. 10631

Practical points

• The pediatric setting does not make the ventilator safe on its own. Confirm the weight or height entered, the tidal volume, the pressure limit, and the alarms.
• If there is a leak around the endotracheal tube, a larger starting volume is sometimes used. One regional PICU guideline suggests 10 to 12 mL/kg with a leak, then reducing it later. I only saw a snippet of that guideline and did not verify it.
• Pediatric ARDS is debated. PALICC notes there has never been a randomized trial of tidal volume restriction in pediatric ARDS, and some studies showed lower mortality with larger tidal volumes. - Miller's Anesthesia, 10e

Recent evidence