Analgesia

Morphine CRI

Moderate-to-severe acute pain in dogs: postoperative, perioperative, neoplastic, soft-tissue trauma, peritonitis, pancreatitis. MLK multi-modal protocol uses morphine as the opioid backbone. Less favored in cats due to dysphoria. Methadone, fentanyl, or hydromorphone are typically preferred.

Stock: 5 mg/mL (5000 µg/mL); 15 mg/mL stock also available

How this calculator works

Enter the patient's weight, dose, and bag concentration. The calculator returns the pump rate to deliver that dose at the chosen concentration. Default prep is 100 µg/mL (25 mg morphine in a 250 mL bag); presets cover 50–200 µg/mL across patient sizes.

After you compute, the result panel shows a loading-dose panel: 0.1–0.3 mg/kg IV given slowly over 5+ minutes before starting the CRI. Many practitioners give the load IM rather than IV to avoid histamine release.

Pure µ-opioid agonist. Watch for respiratory depression, sedation, panting, and GI ileus at higher rates. In cats, dysphoria is more likely than in dogs at standard µ-opioid doses; methadone, fentanyl, or hydromorphone are typically preferred.

Species

Dog Cat

Weight

lb kg

Dose (mg/kg/hr)

Dogs: 0.1–0.4 · Cats: 0.05–0.1 mg/kg/hr

Bag preparation

100 µg/mL

25 mg (5 mL of 5 mg/mL stock) into a 250 mL bag of 0.9% NaCl

Use a different concentration

All preparations are pharmacologically equivalent. The default (100 µg/mL) fits the most common clinical use case. The alternatives below cover situational needs.

100 µg/mL (default) 25 mg (5 mL of 5 mg/mL stock) into a 250 mL bag of 0.9% NaCl Standard prep for medium dogs at typical CRI doses.

200 µg/mL 50 mg (10 mL of 5 mg/mL stock) into a 250 mL bag of 0.9% NaCl More concentrated for larger dogs or higher CRI rates.

50 µg/mL 12.5 mg (2.5 mL of 5 mg/mL stock) into a 250 mL bag of 0.9% NaCl Lower concentration for small patients or low-rate infusions.

Awaiting input

Enter a patient weight to see the result.

Reference

How the calculation works

Morphine CRI is dosed in mg/kg/hr. Because the prepared CRI concentration is expressed in µg/mL, the formula needs a × 1000 to convert the mg dose into µg before dividing:

$$\text{mL/hr} = \frac{\text{weight}_{\text{kg}} \times \text{dose}_{mg/kg/hr} \times 1000}{\text{concentration}_{\mu g/mL}}$$

Patient weight (kg) times dose (mg per kg per hour) gives mg per hour. Multiplying by 1,000 converts mg to µg so the units match the bag concentration. Dividing by µg/mL yields mL per hour.

Worked example with current inputs

Enter a patient weight to see the worked example.

Reference

Recommended dilutions

Target concentration	Dilution	When useful
100 µg/mL	25 mg (5 mL of 5 mg/mL stock) into a 250 mL bag of 0.9% NaCl	Standard prep for medium dogs at typical CRI doses.
200 µg/mL	50 mg (10 mL of 5 mg/mL stock) into a 250 mL bag of 0.9% NaCl	More concentrated for larger dogs or higher CRI rates.
50 µg/mL	12.5 mg (2.5 mL of 5 mg/mL stock) into a 250 mL bag of 0.9% NaCl	Lower concentration for small patients or low-rate infusions.

Compatible with 0.9% NaCl, 5% dextrose, LRS. Preservative-free morphine should be used for epidural / intrathecal routes; standard preservative-containing morphine is fine for IV CRI. Stock 5 mg/mL is most common; 15 mg/mL also exists, verify the vial label before drawing.

Dilution helper — Morphine CRI

Work out how many mL of stock drug and diluent to combine for any target concentration. Stock is pre-filled for Morphine CRI; change it if you're using a different vial.

Stock concentration (µg/mL)

Desired concentration (µg/mL)

Suggestions from the reference table above

Final volume (mL)

Draw up

Enter stock, target concentration, and final volume.