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period after surgery; pain relief was the same but the incidence of pruritus was lower
compared with PCA hydromorphone (Bell et al, 2007 Level II).
Treatment algorithms for intermittent SC morphine using age‐based dosing are available
(Macintyre & Schug, 2007).
Continuous infusions of opioids via the SC route were as effective as continuous IV infusions
(Semple et al, 1996 Level II).
6.3.2 Non-selective non-steroidal anti-inflammatory drugs and
coxibs
There are only a limited number of nsNSAIDs or coxibs available for IM injection at present
and fewer still where Level I evidence for individual efficacy is available. Ketorolac and
parecoxib IM are effective analgesic agents (Smith et al, 2000 Level I; Lloyd et al, 2009 Level I).

6.4 RECTAL ROUTE

Rectal administration of drugs is useful when other routes are unavailable. It results in uptake
into the submucosal venous plexus of the rectum, which drains into the inferior, middle and
superior rectal veins. Drug absorbed from the lower half of the rectum will pass into the
inferior and middle rectal veins and then the inferior vena cava, bypassing the portal system.
Any portion of the drug absorbed into the superior rectal vein enters the portal system,
subjecting it to hepatic first‐pass metabolism.
CHAPTER 6 absorption, possible rectal irritation and cultural factors. Some suppositories should not be
Potential problems with the rectal route of drug administration relate to the variability of
divided as the drug may not be evenly distributed in the preparation. Contraindications to the
use of this route include pre‐existing rectal lesions, recent colorectal surgery and immune
suppression. Whether the drug is administered to a patient who is awake or under
anaesthesia, it is important to obtain prior consent from the patient or guardian.

6.4.1 Opioids
In most instances similar doses of rectal and oral opioids are administered, although there
may be differences in bioavailability and the time to peak analgesic effect for the reasons
outlined above.
In cancer patients no differences in either pain relief or adverse effects were found in a
comparison of oral and rectally administered tramadol (Mercadante et al, 2005 Level II).
6.4.2 Non-selective non-steroidal anti-inflammatory drugs

Rectal administration of nsNSAIDs provides effective analgesia (Tramer et al, 1998 Level I).
Local effects such as rectal irritation and diarrhoea werereported following use of the rectal
route, but other commonly reported adverse effects such as nausea, vomiting, dizziness and
indigestion were independent of the route of administration (Tramer et al, 1998 Level I).
In a study comparing oral and rectal indomethacin (indometacin) given over a period of
2 weeks, the degree of gastric erosion at endoscopy was the same (Hansen et al, 1984 Level II).
Consequently, there appears to be no advantage in using nsNSAID suppositories if the oral
route is available (Tramer et al, 1998 Level I).

158 Acute Pain Management: Scientific Evidence