The oral route is the preferred route of analgesic administration because it is the
most convenient and cost-effective. Oral opioids are available in tablet,
capsule, and liquid forms and in immediate and controlled-release formulations;
morphine is available in immediate and controlled-release forms.
Controlled-release tablets become immediately released when crushed and are
therefore not appropriate for patients who are unable to swallow whole tablets.
A small percentage may require alternate routes during their illness and when
they are unable to swallow, such as during mucositis or in the terminal phase.
Coyle, Adelhardt, Foley, et al. (1990) found that many patients required more
than one route of administration to maintain pain control in the last 4 weeks
of life. When patients cannot take medications orally, other noninvasive routes
such as rectal or transdermal routes should be tried. During intravenous and
subcutaneous administration, local irritation of the skin or vein may occur.
Therefore, parenteral routes should be used only when simpler, less demanding,
and less costly methods are inappropriate or ineffective.
Tolerance and Physical Dependence
Patient-Controlled Analgesia (PCA)