Enkephalinomimetic drugs - Therapeutic uses
Indications
The prescription of an analgesic constitutes a supportive care for pain. Whenever possible, an etiological treatment, i.e. acting on the cause of pain, must be considered, alone or combined with the analgesic treatment. But each time a patient presents acute or persistent pains, the prescription of an analgesic is the rule.
The principal therapeutic uses of opioid analgesics are as follows:
- Acute pain
- biliary and renal colics, but in this case their spasmogenic action must be avoided by the concurrent administration of an antispasmodic
- myocardial infarction
- acute pulmonary edema
In the event of a very painful abdominal syndrome, it remains advisable to make the diagnosis of the cause before prescribing morphine.
- Chronic pain
Among cancer patients, when analgesics such as acetaminophen are no longer sufficient, one usually uses morphine. It is given by oral route, with high dosage to compensate for its low bioavailability (25%), at the frequency required to avoid the reappearance of the pain.
- Peroperative and postoperative p ains, including obstetrical interventions. In this last case, morphine is often administered by peridural route.
- Treatment of drug-addiction where methadone and buprenorphine can be used as substitutes of morphine and heroin.
Adverse effects
Morphine type analgesics present a certain number of disadvantages:
- Respiratory depression, especially in patients with respiratory insufficiency.
- Addiction leading to drug-addiction. But the risk of addiction should not deprive patients who suffer from the efficacy of morphine, more especially as the outbreak of an addiction is not very frequent when the medical treatment is well controlled
- The risk of masking abdominal signs of a diagnosis requiring surgery.
- A spasmogenic effect in biliary tract which can be avoided by the administration of an antispasmodic.
- Constipation which is the most frequent adverse effect, especially in the elderly.
It is traditional in patients treated by MAO inhibitors to avoid the use of morphine, although the interactions between the new morphine drugs and the new MAO inhibitors are not very well-known.
Morphine poisoning is characterized by the triad: respiratory depression, pinpoint pupils, altered consciousness of all levels right down to coma.
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