Morphine sulphate

Controlled Substances

Only midwives who have completed the “Opioids and Benzodiazepines: Safe Prescribing for Midwives” course may independently prescribe controlled substances. 

Morphine sulphate (morphine) is an opioid. It binds to opiate receptors in the CNS, causing inhibition of pain pathways, altering perception and pain response and producing generalized CNS depression. Morphine has a similar analgesic action to Demerol® (Meperidine), but with less nausea and fewer significant side effects for the neonate.

Indications and Clinical Use:

Midwives may only prescribe, order and administer morphine in hospital on their own authority for the purpose of pain relief in non-progressive or prodromal labour and in early active labour. Use under any other circumstance must be on the order of a physician. Morphine can be administered intramuscularly for therapeutic rest or as an analgesic for pain relief in labour.

Intramuscular (IM) morphine is often administered with dimenhydrinate (Gravol®) to counteract the side effects of nausea and vomiting. The two drugs are compatible in a syringe for only 15 minutes.

As morphine is more sedating and has a longer half-life than fentanyl, it may be a more beneficial early labour analgesic when intramuscular administration will provide longer relief, or for those who do not want IV access in labour.

Contraindications:

Hypersensitivity to morphine sulfate or any component of the formulation; alcohol use; seizure disorders.

Morphine should not be used in the presence of an atypical or abnormal fetal heart rate, in advanced labour or the second stage of labour.

Warnings and Precautions:

Naloxone should be readily available for administration. Physician consultation immediately after administration is required if naloxone needs to be given.

Morphine should be used with caution in patients with a history of substance use, alcohol use or hepatic impairment, or in patients with renal impairment, pre-existing respiratory compromise (hypoxia and/or hypercapnia), seizure disorders or thyroid dysfunction.

Monitoring:

Determine cervical dilation prior to administration; generally a nullipara should be less than 7 cm and a nullipara or multipara less than 4 cm. Assess well-being prior to morphine administration, 15 minutes post administration and according to hospital protocol thereafter. Protocols in some centers allow discharge home during early labour when IM morphine has been administered and there are no health concerns.

Pregnancy:

Human Data Suggest Risk

Opioid use during organogenesis is associated with a risk for congenital birth defects. Placental transfer is rapid. Neonatal withdrawal and potential respiratory depression is a risk with use of morphine late in pregnancy.

Lactation:

Category L3 – Limited Human Data – Probably Compatible (not the preferred narcotic in lactation)

Morphine is considered suitable for short term use in lactation; however, about 9-35% of the dose is known to enter breastmilk. This medication also has an active metabolite, thus the lowest effective dose should be given for the shortest possible period of time. The infant should also be monitored for signs of sedation such as not waking up to feed at regular intervals. If an ongoing narcotic is required postpartum consider other alternative agents such as hydromorphone.

Adverse Reactions:

Morphine crosses the placental barrier and can produce depression of respiration and psycho-physiologic functions in the neonate. As with other opioids, morphine can depress respirations during labour and in the neonate. The larger the adult dose administered during labour, the greater the risk of neonatal respiratory depression. As with any narcotic, watch for aspiration, drowsiness, hypotension and/or obtunded reflexes in addition to respiratory depression and urinary retention.

Adult: Circulatory depression, flushing, shock, bradycardia, hypotension, drowsiness, dizziness, confusion, headache, pruritus, chest pain, hypertension, tachycardia, vasodilation, amnesia, anxiety, hallucination, nervousness, restlessness, seizure, slurred speech, rash.

Dosage and Administration:

10-15 mg IM every 4 hours; or

2-5 mg dose IV bolus every 10 minutes prn for 1-2 hours of relief

Maximum daily dose 45 mg

Morphine has a half-life of 2-4 hours in adults and a half-life of 9 hours in neonates (or longer in premature neonates). Morphine may be used up to 4 hours prior to anticipated delivery. Most infants delivered 3 hours after a dose have been found to have no detectable levels in cord blood samples.

IM administration may be particularly appropriate for the nullipara seeking pain relief in early active first stage. Morphine should not be administered subcutaneously as consistency of uptake and effectiveness cannot be determined. Morphine is often administered with dimenhydrinate (Gravol®) to counteract the side effects of nausea and vomiting.

Onset of Action:

IM: 15-20 minutes

Time to peak effect: 40-50 minutes

IV: 5-10 minutes

Half-Life:

Adult – IM: 2-4 hours

IV: 2-4 hours

Neonate – 9 hours and 18 hours metabolite

Prescription:

Morphine sulphate may only be prescribed in hospital for the specific purposes listed here following hospital protocols.