Morphine hydrochloride mixture is commercially available in 2 mg/ml, 5 mg/ml and 10 mg/ml strengths. Morphine sulphate or morphine hydrochloride can be prepared by a pharmacist at any required strength up to 30 mg/ml, which is the limit of solubility. The inclusion of preservatives in commercially available preparations has overcome the earlier problem of a limited shelf life.
No other drugs should be included in a morphine mixture. Drugs which were included in the past were antiemetics, aspirin, chlorpromazine and cocaine. One of the great advantages of morphine mixture is that the dose can be increased or decreased easily according to need or side effects. If the mixture contains other drugs then the dosage of these drugs will also be varied, leading to either inadequate dosage or toxicity. The traditional use of cocaine in Brompton's cocktail is not to be recommended as it adds nothing to the analgesic properties and may cause confusion, dysphoria and insomnia in the frail and elderly.
Breakthrough pain-Breakthrough pain is treated with extra doses of mixture taken as often as necessary to control the pain. The dose is the same as the 4-hourly dose; if there is concern about opioid side effects, 50% of the 4-hourly dose can be used. If breakthrough pain occurs within an hour of the next 4-hourly dose, adequate pain relief may be achieved by simply taking the next dose a little early. If the tendency to 3-hourly requirement continues, the 4-hourly dose should be reviewed.
Incident pain-Incident pain is pain which occurs only in certain circumstances, such as after a particular movement or on standing. Incident pain is treated in the same manner as breakthrough pain. If the incident pain can be predicted, the additional treatment can be given prophylactically, 30 or 60 minutes earlier, to lessen or prevent the pain.
Adjustment of dose-If pain relief is inadequate or more than occasional backup doses are required, the dose is titrated upwards. If side effects are troublesome, the dose is reduced. Patients with pain worse at night or those troubled by sedation during the day can have a lower dose by day and a higher dose at night.
• The correct dose of morphine is that which controls the pain whilst causing tolerable side effects, titrated for each individual patient.
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