Disclaimer to the Online Edition
This Manual has been designed for use in the NICU at London Health Sciences Centre (LHSC), London, Ontario, Canada, and represents clinical practice at this institution. The information contained within the Manual may not be applicable to other centres. If users of this Manual are not familiar with a drug, it is recommended that the official monograph be consulted before it is prescribed and administered. Any user of this information is advised that the contributors, Editor and LHSC are not responsible for any errors or omissions, and / or any consequences arising from the use of the information in this Manual.
Morphine
Indication
- first line agent for the treatment of moderate to severe pain, and to provide sedation for infants who are struggling against the ventilator
Pharmacology
- A naturally occurring opioid which is still obtained from opium or poppy straw
- Well absorbed in the GI tract but subject to high first-pass effect
- Little morphine is excreted unchanged; its major metabolic pathway is hepatic glucuronidation
- Acts on different opioid receptors in the CNS and bowel to produce its major pharmacological effects (analgesia, drowsiness, respiratory depression, decreased gastrointestinal (GI) motility, vomiting)
- Causes histamine release which can result in systemic vasodilation
Side Effects
- Respiratory depression, vomiting, constipation, urinary retention, hypotension, bradycardia, sweating, decreased GI motility
Precautions
- Physical dependence and tolerance can occur; staff should be aware of this; an infant who is receiving a continuous infusion should be weaned; the infusion should not be stopped abruptly
Miscellaneous
- Although it is not recommended that medications and TPN (amino acid/dextrose mixture and lipid) be mixed, in some situations there is no alternative. Morphine and TPN (the amino acid/dextrose component) have been reported in the literature to be physically compatible. A morphine infusion has successfully (no evidence of physical incompatibility) been "y'd" in with a mixture of amino acid/dextrose and lipid in this unit. In all instances, however, the IV lines should be carefully inspected for any signs of incompatibility (precipitate, change in colour, haze).
Dose
- Intermittent dosing
- 50 to 200 mcg/kg (0.05 to 0.2 mg/kg)
IV push over at least 5 minutes, SC q2 to 4h
(in most instances a dose up to 100 mcg/kg q4h has proven adequate) - because the oral bioavailability of morphine is variable, the ORAL dose of morphine should be 3 to 5 times the IV dose
- 50 to 200 mcg/kg (0.05 to 0.2 mg/kg)
- Continuous infusion
- Consider a loading dose of 50 to 100 mcg/kg before starting an infusion
- 10 to 20 mcg/kg/h
Sample Calculation
- To Prepare an infusion of 20 mcg/kg/h
- Morphine Dose (mg) = (Baby's Weight in kg) in 50 mL D5W
- Infusion rate = 1 mL/h
- e.g. Baby's Weight = 3.2 kg
- Morphine Dose (mg) = 3.2 mg in 50 mL D5W
- Infusion Rate = 1 mL/h (delivers 20 mcg/kg/h)
References
- Koren G, Butt W, Chinyanga H et al Postoperative morphine infusion in newborn infants - assessment of disposition characteristics and safety. The Journal of Pediatrics 1985; 107: 963-967.
- The Pharmacological Basis of Therapeutics, Gilman AG, Goodman LS Rall TW and Murad F (eds), 7th Edition, MacMillan, 1985
- Roberts, RJ: Drug Therapy in Infants, W.B. Saunders, Toronto, 1984.
- Trissel L.A.: Handbook on Injectable Drugs, American Society of Hospital Pharmacists 1988.
MORPHINE
** Note the strength of morphine **
Morphine * 2mg/mL *
| Dose | Volume |
| 0.1 mg | 0.05 mL |
| 0.2 mg | 0.1 mL |
| 0.3 mg | 0.15 mL |
| 0.4 mg | 0.2 mL |
| 0.5 mg | 0.25 mL |
| 0.6 mg | 0.3 mL |
| 0.7 mg | 0.35 mL |
| 0.8 mg | 0.4 mL |
| 0.9 mg | 0.45 mL |
| 1.0 mg | 0.5 mL |
For doses Less than 0.1 mg (0.05 mL), a dilution should be made as follows:
Morphine: 1 mL of 2mg/mL + Diluent: 9 mL (e.g. D5W, 0.9 % NaCl)
| therefore concentration of diluted morphine | = | 2 mg/10 mL |
| = | 0.2 mg/mL |
MORPHINE * 0.2 mg/mL *
| 0.01 mg | 0.05 mL |
| 0.02 mg | 0.1 mL |
| 0.03 mg | 0.15 mL |
| 0.04 mg | 0.2 mL |
| 0.05 mg | 0.25 mL |
| 0.06 mg | 0.3 mL |
| 0.07 mg | 0.35 mL |
| 0.08 mg | 0.4 mL |
| 0.09 mg | 0.45 mL |
Morphine pre-mixed bags
2 mg/100mL
| 2mg/100mL | = = | 2,000 mcg/100mL 20 mcg/mL |
Sample No. 1
- 1 kg infant
- want: 10 mcg/kg/hr
- .need 10 mcg (0.5 mL) per hour
- Run at 0.5 mL/hr
Sample No. 2
- 1.5 kg infant
- want: 20 mcg/kg/hr
- need (1.5 kg)(20 mcg/kg/hr) = 30 mcg/hr
| Concentration | = = | 20 mcg/mL 30 mcg/1.5 mL |
| ..Run at 1.5 mL/hr |