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Opioids are associated with a diverse array of side effects (Table 1). The
management of opioid side effects should be viewed as a fundamental aspect
of opioid therapy. Because opioid responsiveness is determined by the balance
between analgesia and side effects, effective management of problematic
side effects will increase the likelihood of successful therapy.
Table 1: Side Effects Associated With Opioid Therapy (.pdf)
The most common opioid side effects during long-term therapy involve the
gastrointestinal tract and the central nervous system. Constipation occurs
very commonly and is often persistent (Table 2). Somnolence and mental clouding
often is experienced when therapy is initiated or the dose is increased.
The latter effects typically dissipate over a short time, but some patients
experience persistent effects. Indeed, the development of persistent somnolence
or mental clouding is the usual reason for treatment failure, and the aggressive
treatment of these side effects with psychostimulant drugs is considered
a strategy for addressing the poorly responsive patient (Table 3). The decision
to try a psychostimulant, particularly one of the stimulants that are controlled
prescription drugs (e.g., methylphenidate, dextroamphetamine, or amphetamine),
should be made after a careful assessment of the risks. These drugs may
not be preferred, or may need close monitoring during an initial trial,
because of their capacity to cause anxiety or tremulousness, anorexia, insomnia,
tachycardia or hypertension. They are also potentially abusable by predisposed
individuals and the evaluation prior to therapy also should assess the likelihood
for responsible drug use and the potential need for close monitoring of
drug-related behaviors.
The greatest experience is with methylphenidate, a trial of which usually
begins with a dose of 5-10 mg in the morning and, if needed, midday. Alternatively,
a single morning dose of an extended-release formulation can be used. In
medically ill fragile patients, the initial dose of methylphenidate may
be 2.5 5 mg once or twice daily. This dose is then gradually increased until
favorable effects occur or toxicity supervenes. Most patients require less
than 60 mg per day, but some require higher doses.
Dextroamphetamine and a compound of amphetamine congeners are dosed in a
manner identical to methylphenidate. A newer drug, modafinil carries a lesser
risk of sympathomimetic effects and is usually initiated at a dose of 100-200
mg/d, and then titrated. An older drug, pemoline, is now used less commonly
because of an association with a rare hepatopathy.
Table 2: Approaches to the Management of Opioid-Induced Constipation (.pdf)
Table 3: Approaches to the Management of Opioid-Induced Somnolence and Cognitive Impairment (.pdf)
References
Bruera E, Brenneis C, Paterson AH et al. Use of methylphenidate as an adjuvant
to narcotic analgesics in patients with advanced cancer. J Pain Symptom
Manage 1989;4:3-6.
Derby S, Portenoy RK. Assessment and management of opioid-induced constipation.
In Portenoy RK, Bruera E, eds. Topics in Palliative Care. New York: Oxford
University Press; 1997:95-112.
Kurz A, Sessler DI. Opioid-induced bowel dysfunction: pathophysiology and
potential new therapies. Drugs 2003; 63: 649-671
Lawlor PG. The panorama of opioid-related cognitive dysfunction in patients
with cancer: a critical literature appraisal. Cancer 2002;94:1836-53
Portenoy RK: Management of common opioid side effects during long-term therapy
of cancer pain. Ann Acad Med Singapore 1994;23:160-170 |
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