Morphine

CLINICAL USE

Opiate analgesic

DOSE IN NORMAL RENAL FUNCTION

5–20 mg every 4 hours (higher in very severe pain or terminal illness)PR: 15–30 mg every 4 hours

PHARMACOKINETICS

Molecular weight :285.3 (758.8 as sulphate); (774.8 as tartrate)

%Protein binding :20–35

%Excreted unchanged in urine : 10

Volume of distribution (L/kg) :3–5

half-life – normal/ESRD (hrs) :2–3/Unchanged

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : 75% of normal dose

10 to 20 : Use small doses, e.g. 2.5–5 mg and extended dosing intervals. Titrate according to response

<10 : Use small doses, e.g. 1.25–2.5 mg and extended dosing intervals. Titrate according to response

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Not dialysed. Dose as in GFR <10 mL/min

HD :Dialysed – active metabolite removed significantly. Dose as in GFR <10 mL/min

HDF/high flux :Dialysed – active metabolite removed significantly. Dose as in GFR <10 mL/min

CAV/VVHD :Dialysed. Dose as in GFR=10–20 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Antidepressants: possible CNS excitation or depression with MAOIs – avoid concomitant use, and for 2 weeks after stopping MAOI; possible CNS excitation or depression with moclobemide; increased sedative effects with tricyclics

Antivirals: concentration possibly increased by ritonavirSodium oxybate: enhanced effect of sodium oxybate – avoid concomitant use

ADMINISTRATION

Reconstition

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Route

Oral, SC, IM, IV, PR

Rate of Administration

2 mg/minute. (Titrate according to response)

Comments

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OTHER INFORMATION

Extreme caution with all opiates in patients with impaired renal functionPotential accumulation of morphine-6- glucuronide (a renally excreted active metabolite, more potent than morphine) and morphine-3-glucuronide. Half-life of morphine-6-glucuronide is increased from 3–5 hours in normal renal function to about 50 hours in ERFENSURE NALOXONE READILY AVAILABLESome units avoid slow release oral preparations as any side effects may be prolonged.

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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