Calculate Diphenhydramine (Benadryl) Dosage for Dogs
Understanding Diphenhydramine (Benadryl) Dosage for Dogs
Diphenhydramine, commonly known by the brand name Benadryl, is an over-the-counter antihistamine often used to treat allergies, motion sickness, and anxiety in dogs. **It is crucial to consult a veterinarian** before administering any human medication to a pet, as dosage errors can be dangerous.
This calculator provides an estimated dose based on the standard veterinary recommendation. Always use plain diphenhydramine formulations, avoiding capsules or liquids that contain **acetaminophen (Tylenol)** or **decongestants**, as these ingredients are highly toxic to dogs.
The Standard Dosage Formula
The dosing of diphenhydramine for dogs is based directly on the animal's body weight. The standard therapeutic dose used by veterinarians is:
$$Dose_{mg} = Weight_{lb} \times 1 \frac{mg}{lb}$$
If the dog's weight is entered in kilograms, the formula converts it to pounds first, where $1 \text{ kg} \approx 2.2046 \text{ lb}$. The formula simplifies to:
$$Dose_{mg} = Weight_{kg} \times 2.2 \frac{mg}{kg}$$
The calculated dose ($Dose_{mg}$) is the total amount of medication needed per administration. This dose is typically given two to three times per day (every 8 to 12 hours).
Calculating the Final Volume or Tablet Amount
Once the total dose in milligrams is determined, the next step is to convert this into the actual volume (mL) or number of tablets to administer, based on the product's concentration ($C_{mg}$):
For Tablets:
To find the number of tablets ($T$) required, divide the total dose by the strength of a single tablet ($S_{tablet}$):
$$T = \frac{Dose_{mg}}{S_{tablet}}$$
It is important to round the result to the nearest quarter of a tablet (e.g., $1, 1/4, 1/2, 3/4, 2$, etc.) for precise and safe administration.
For Liquid Solutions:
To find the volume in milliliters ($V_{mL}$) required, divide the total dose by the concentration of the liquid ($C_{liquid}$) in milligrams per milliliter ($mg/mL$):
$$V_{mL} = \frac{Dose_{mg}}{C_{liquid}} \quad \left( C_{liquid} \text{ in } \frac{mg}{mL} \right)$$
If your liquid concentration is given as $12.5 \text{ mg}/5 \text{ mL}$, the concentration $C_{liquid}$ is $2.5 \text{ mg}/\text{mL}$. **Use calibrated measuring tools** for administering liquid medication.