What is the recommended dose of Benadryl (diphenhydramine) for a 28 kg male?

Benadryl Dosing for a 28 kg Male

For a 28 kg male, the recommended dose of diphenhydramine (Benadryl) is 1-2 mg/kg per dose, which translates to 28-56 mg, with a maximum single dose of 50 mg. 1

Standard Dosing Algorithm

For this specific patient:

• Weight-based calculation: 1-2 mg/kg × 28 kg = 28-56 mg per dose 1
• Apply maximum cap: The dose should not exceed 50 mg per single administration 1
• Practical recommendation: Administer 25-50 mg per dose, depending on indication and severity

Route-Specific Considerations

Parenteral (IV/IM) administration:

• Use 1-2 mg/kg per dose (maximum 50 mg) when rapid onset is needed 1
• Onset of action occurs within several minutes, with effects lasting 4-6 hours 1

Oral administration:

• Peak plasma concentration occurs at approximately 1.5 hours after dosing 2
• Weight-age dosing schedules across pediatric populations show consistent pharmacokinetics 2

Safety Thresholds and Toxicity

Critical dosing threshold for toxicity:

• Doses ≥7.5 mg/kg (210 mg for this 28 kg patient) warrant emergency department referral 3
• For patients 6 years and older, referral is indicated at 7.5 mg/kg OR 300 mg, whichever is less 3
• This patient's toxic threshold would be 210 mg based on weight 3

Monitoring Requirements

Essential monitoring parameters:

• Changes in mental status beyond mild drowsiness or mild stimulation 3
• Excessive sedation, particularly when combined with other medications 1
• Anticholinergic effects: dry mouth, blurred vision, urinary retention, constipation 1
• Respiratory status and level of consciousness 1

Common Pitfalls to Avoid

Do not exceed maximum single dose:

• Even though weight-based calculation may suggest 56 mg, the 50 mg maximum cap must be respected 1

Avoid in certain clinical scenarios:

• Do not use for chronic insomnia, as not recommended by the American Academy of Sleep Medicine 4, 5
• Exercise caution with concomitant sedating medications due to additive effects 1
• Consider alternative non-sedating antihistamines when sedation is undesirable 4

Recognize moderate-to-severe symptoms requiring immediate referral:

• Agitation, hallucinations, abnormal muscle movements, loss of consciousness, seizures, or respiratory depression all warrant emergency department evaluation 3

Duration and Frequency

• Effects last 4-6 hours for parenteral administration 1
• Dosing frequency should account for the duration of action and clinical indication
• For unintentional ingestions, if asymptomatic after 4 hours, emergency referral is not needed 3