Routes of Administration
1. Oral route is the preferred route of analgesic administration because
it is the most convenient and cost-effective. EXACTLY THE SAME RESULTS CAN
BE OBTAINED WITH ORAL ADMINISTRATION AS WITH PARENTERAL IF
BIOTRANSFORMATION IS TAKEN INTO ACCOUNT. If the oral route is impractical
or unavailable, rectal and transdermal administration are minimally
invasive alternatives . {See Table III- Method for Converting Other
Opioids to Eqianalgesic Dose of Morphine [Pages___ ] and TABLE IV-Oral and
Parenteral Opioid Analgesic Dose Equivalencies and Relative Potency of
Drugs as compared with 10MG Morphine IM for Treatment of Pain. [__ ]}.
2. Rectal is an alternative route for patients experiencing nausea and
vomiting or fasting. Neutropenia and thrombocytopenia are relative
contraindications. This route is not useful in the presence of diarrhea or
among those who are physically unable to insert the suppository. Colostomy
or similar stoma can be used provided the flow of effluent is slow enough
to allow absorption. {e.g., Dilaudid© 2 mgs po is equipotent to 2 mgs per
rectum}.
3. Transdermal administration bypasses gastrointestinal absorption.
Fentanyl (Duragesic©) is the only opioid available by this route. The
maximum recommended dose is 300 ug/hr. Patients requiring larger doses
should be considered for equipotent dose of an oral or parenteral/SQ dose.
Plasma levels rise slowly over 12-18 hours after transdermal patch
placement and slowly fall off 20-24 hours after removal. Therefore, a
transdermal system is inappropriate for rapid dose titration and only
considered in non-opioid naive patients who have relatively stable pain.
As with controlled release opioids, immediate release opioids should be
provided for the treatment of breakthrough pain. Dosage can be determined
based on the daily morphine equivalent dose {See Table II Equianalgesic
doses for Converting Morphine to Transdermal Fentanyl, Page--}.
4. Transnasal is an alternative route when the oral route is unavailable.
The transnasal route provides for rapid absorption and action. The only
commercially available transnasal formation is the mixed opioid
agonist-antagonist, butorphanol {Stadol©}. It is primarily used in the
treatment of acute headaches. Butorphanol, regardless of the route, is not
recommended for use in cancer pain treatment.
5. Subcutaneous or intravenous continuous infusions may benefit patients
with persistent nausea or vomiting, dysphagia or difficulty swallowing,
intestinal obstruction, malabsorption, analgesic requirements which make
oral dosing impractical, as well as patients who require rapid titration
of opioids. Medications may be given as repeated intermittent bolus doses
or by continuous infusion. Intravenous provides almost immediate
analgesia; subcutaneous may require up to 15 minutes for effect. Bolus IV
dosing provides a shorter duration of action than other routes. Continuous
infusions provide steady blood levels. The use of an infusion pump may be
the best strategy for delivery of a continuous infusion.
Patient-controlled analgesia (PCA) devices can be used to combine
continuous infusion with intermittent bolus doses, allowing more flexible
pain control. It is recommended that the hourly SQ volume limit not exceed
5 cc. Medications can be concentrated to maintain SQ volume limits;
maximal concentrations: fentanyl 50 ug/ml, morphine 50 mgs/ml,
hydromorphone 50 mgs/ml. Intravenous and subcutaneous infusions can be
administered at home provided that the caregiver received appropriate
instruction. The subcutaneous site should be inspected and possibly be
rotated every 48-72 hrs in neutropenic patients to minimize risk of site
infection. {See Table III-Method for Converting Other Opioids to
Equianalgesic Dose of Morphine [Pages__] and TABLE IV-Oral and Parenteral
Opioid Analgesic Dose Equivalencies and Relative Potency of Drugs as
Compared with 10 MG Morphine IM for Treatment of Pain [___]}.
6. Intramuscular injections should be avoided because injections are
painful and inconvenient, and absorption is erratic. Thrombocytopenic
patients are a risk for hematomas at the injection site and neutropenic
patients or individuals on chronic steroid therapy are at increased risk
for site infection and systemic infection. If this route is used, a
concentrated opioid should be given to keep the volume of injection as
small as possible. Hydromorphone (Dilaudid HP©) is available in a 10 mg/ml
form. This is the most concentrated commercially available injectable
opioid. This preparation may also be administered subcutaneously.
7. Intraspinal and intraventricular administration are options if maximal
doses of opioids and adjuvants administered through other routes are
ineffective or produce intolerable side effects {e.g., nausea/vomiting,
excessive sedation, confusion}. Opioids can be administered via indwelling
percutaneous or tunneled catheters into the epidural or intrathecal space.
Intraventricular opioids are given via an Ommaya© reservoir surgically
placed in the lateral ventricle. Administration can be by intermittent
bolus injections or continuous infusion with bolus dosing. One advantage
of these routes is that the equipotent dosing is far less in comparison to
systemic delivery; less total dose may reduce side effects. Secondly, the
duration of action is longer than with any other route of administration.
Proper patient selection and consideration of long term maintenance are
critical.
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