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Dear Doctor,
The bearer of this letter is participating in a
methadone maintenance treatment program at the Community Alcohol
and Drug service. Like other members of the community they need treatment
for their medical,surgical and dental conditions.
Many are very reluctant to provide information to other health professionals
about their addiction and treatment
because of previous judgmental responses. The purpose of this brief letter
is to touch on the most common problems encountered and to offer guidance
for treatment.
What are the benefits of methadone treatment?
Methadone has been used in treatment of opioid
dependence for over 35 years. It has been found to be both
effective and safe in long term administration. An adequate individualised
dose of methadone eliminates drug
craving, prevents the onset of withdrawing and blocks (through opioid cross
tolerance) the effects of other opioids
such as heroin or morphine.
Efficacy of treatment is based on elimination of or
reduction in illegal activities, improved employment, pro-social behaviour and improved general health. Such treatment has been shown to be
effective in reducing the spread of HIV
and other infections. Dramatic reductions in mortality rates are seen in
methadone maintained individuals in comparison
with the untreated addict population.
Pharmacodynamics and effects.
The methadone maintained patient develops tolerance to
analgesic, sedative and euphoric effects of the maintenance
dose of methadone. Methadone has a long half-life, which makes single daily
dosing possible.
Methadone has a relatively blood plasma level curve that will prevent the
onset of abstinence symptoms for over 24
hours without causing any sedation, euphoria or impairment of function.
Beware.....
Opioid partial agonist and agonist/antagonist drugs
such as buprenorphine (Temegesic), pentazocine (Fortral)
and nalbuphine (Nubain) should never be used in the methadone tolerant
individual. Severe opiate withdrawal
syndrome can be precipitated by drugs of this type.
Both dextropropxyphene (doloxene) and pethidine are known to produce CNS
excitatory metabolies by demethylation.
Because of the higher doses required to achieve analgesia the risk of
seizures are increased.
Dextropropoxyphene and pethidine should be avoided in the maintenance
patients for this reason and also because
of sought after psychotropic effects.
It goes without saying that the administration of opioid agonist drugs
should be closely supervised in terms of quantities and duration. Similar precautions are indicated in the prescribing of
sedative/drugs or benzodiazepines ( eg. Diazepam,
temazepam, clonazepam etc).
Analgesia.
A common and very serious problem is the failure to
provide adequate treatment of pain in methadone maintained
patients. Relief of acute pain depends on maintaining the established
tolerance level with methadone and then providing
additional analgesia. Local, regional, epidural or spinal anaesthesia can be
very useful in these patients.
Studies have shown that exposure to adequate doses of
narcotics for the relief of acute severe pain does not
compromise treatment of the addiction. This is done by continuing oral
maintenance (methadone mixture is usually prescribed as 2 - 5 mgs per ml) if possible and using two to three times
the "standard" dose of narcotic ( for a start ).
Analgesic effectiveness must be regularly assessed. If
oral therapy is not possible an equivalent dose of narcotic to the maintenance methadone dose is given parenterally ( 1 mg oral methadone
is equivalent to 1 mg IV methadone which is the preferable option. If IV methadone is not available 1 mg
methadone is equivalent to 2 mg IV morphine
over a 24 hour period and analgesia given on top of this.
Adjuvant non-narcotic analgesics (paracetamol & NSAIDS
) should be used when pain is not severe and not
contraindicated. In the event of more acute pain the use of opioid agonist
drugs as detailed above is appropriate.
Doses must be individually titrated to ensure adequate analgesia. Best
results are obtained with scheduled dosing
as opposed to PRN or with use of a PCA pump (patient controlled analgesia)
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