Strong opioid analgesics

These opioid analgesics are used for severe pain poorly localized in the internal organs

In the localized pain of lower intensity use weak narcotic or narcotic opioid analgesics (nonsteroidal anti-inflammatory drugs, see Chapter 32). To eliminate the severe pain morphine is administered parenterally, oral administration of morphine is shown in the terminal stages of illness.
Morphine and other opioids have a variety of central effects. Besides pronounced opioid analgesics narcotic analgesics cause a state of euphoria, depression of the respiratory and vasomotor centers (which may lead to orthostatic hypotension), have a sedative effect, encourage the trigger hemoreceptor zone (causing nausea and vomiting). Opioids stimulate the center of the oculomotor nerve, causing a contraction of the pupil - miosis (the exception is pethidine, which has a weak m-anticholinergic activity). Drugs inhibit the cough center, but the severity of this effect does not correlate with their opioid activity. In the application of opioids may be constipation, spasms of the bile ducts and sphincter of Oddi. Morphine can cause histamine liberatsiyu, which leads to vasodilatation and the appearance of skin itch. Morphine is metabolized in the liver by conjugation with glucuronic acid, forming inactive morphine-3-glucuronide and morphine-highly active 6-glucuronide.
Prolonged use of opioid analgesics develops tolerance to them (ie, addiction - reduction in sensitivity to the drug). Such side effects of narcotic analgesics, a contraction of the pupil and constipation, do not improve after prolonged use.

For opioid analgesics develops mental and physical drug dependence, abrupt withdrawal of drugs causing withdrawal symptoms

Diamorphine (heroin, diacetylmorphine) is two times more active than morphine. The body is rapidly converted to the active metabolite 6-atsetilmorfin and more slowly to morphine. In the application of heroin observed pronounced euphoria, nausea, constipation, and hypotension are less pronounced than with morphine.
Methadone is well absorbed when taken orally, has a lasting effect. It is used orally in the treatment of opiate addiction for the prevention of withdrawal syndrome ("breaking").
Pethidine has properties similar to morphine, but shorter acting. When used in doses causing analgesia, depresses the respiratory center, has a weak anti-tussive effect and practically no development of constipation. The drug is highly lipophilic, so its effect develops rapidly. The liver becomes norpetidin pethidine, which can cause a number of side effects (eg, mydriasis, seizures). The combined use of pethidine with MAO inhibitors may cause the appearance of delirium, fever, convulsions and respiratory depression.
Buprenorphine - a partial agonist m-receptors, lipophilic, is effective for sublingual application. The drug has a longer than morphine. Using it may cause prolonged vomiting. Buprenorphine is closely associated with opioid receptors, naloxone, so practically does not eliminate the respiratory depression caused by the use of the drug.
    Nalbufin (agonist to the receptor and receptor antagonist m-) corresponds to morphine analgesic activity and the ability to inhibit the respiratory center, nausea and vomiting if it is applied less frequently observed. When opioid analgesics used in high doses causes dysphoria.

Opioid Analgesics a major group of drugs for the treatment of pain in the postoperative period

Opioid analgesics implement its action through opioid receptors located at spinal and supraspinal levels, and are a major group of drugs for the treatment of pain in the postoperative period.
At the same time after major intracavitary surgery to achieve adequate pain relief in every third patient required administration of opioids in doses exceeding the recommended standard [3].

Increasing the dose of opioid analgesics is accompanied by severe side effects

- drowsiness, respiratory depression, nausea, vomiting, paresis of the gastrointestinal tract, urinary disorders), so it is now recognized that monotherapy with opioid analgesics are not always effective enough, and sometimes even dangerous.
   In addition, the traditional subcutaneous and intramuscular injection is difficult to maintain an optimal concentration of opioids(opioid analgesics) in the plasma, which may be accompanied by a respiratory depression, or inadequate anesthesia.
   Bolus intrathecal opioids or epidural analgesia provides good up to 24 hours, but even small doses of drugs (opioid analgesics) administered (ten times less than with intramuscular injection) may be accompanied by adverse and toxic effects.

Opioid analgesics and chronic pain

For the treatment of pain of low intensity according to WHO recommendations
non opioid analgesics use different, and when pain of moderate or high
the intensity of opioid analgesics. Non-opioid analgesia means
have a predominantly peripheral action at the source of pain, have
Small analgesic potential and therefore only suitable for eliminating weak
pain.

Opioid analgesics are centrally acting analgesics

- implemented through endogenous opioid system of the body at the level of the spinal cord and brain
by inhibiting upstream of pain impulses. They differ from
another in analgesic potential and ability to arrest or reasonable
pain. Thanks to good analgesic properties of opioid analgesics are widely
applied in various fields of medicine dealing with the intense pain,
especially in oncology and surgery.

Common to all opioid analgesics is a sign of non-selective nature of their actions

- ie, along with the analgesia they cause other side effects while
differ from each other on the severity of the various characteristics that
associated with the individual characteristics of their interaction with opioid
receptors. An important condition for proper operation with an opioid analgesics is knowledge their mechanism of action.

Opioid analgesics activate nociceptive system

To date, it is proved that opioid analgesics activate not only the antinociceptive system, but also cause proof activate nociceptive system

    Last seen central sensitization, which is the basis for the activation of excitatory amino acids (glutamate and aspartate) at the level of NMDA-receptors. Impact on the μ-opioid receptors initiates the activation of NMDA-receptors by removing the blocking Mg2 + ions from their receptor channels. This process contributes to the activation of protein kinase C activation Pronotsitseptivnaya exceed in intensity the activity of nociceptive inhibitory systems. Thus, opioid analgesics alone are able to induce delayed hyperalgesia until the development of allodynia (pain perception nebolevyh incentives). We can say that they have on nociception two opposite effects: at the initial stage is dominated by analgesia, which was later replaced by hyperalgesia.
   In conclusion, we present some of the tenets of evidence based medicine, on postoperative use of opioid analgesics (Acute Pain Management: Scientific Evidence, 3-rd edition, 2010):
1. Opioids in high doses can induce hyperalgesia (Grade I)
2. In the treatment of acute pain one opioid has no advantage over the other, although some opioids may have certain advantages in those or other patients (Grade II)
3. The frequency of significant side effects of opioids is a dose-dependent nature of the (Grade II)
4. Age of the patient to a greater extent than its weight, determines the need for opioid analgesics, although there is individual variability (level of evidence IV)

Opioid analgesics optimization methods of drug administration

The most effective efforts to improve the quality of postoperative opioid analgesics usage, based on the optimization methods of drug administration

The most modern method is controlled by the patient's intravenous analgesia (KPVA), most focused on the individual needs of the patient's anesthesia. If necessary, by clicking on the remote device, the patient himself, introduces an additional bolus of analgesic (typically 2 mg of morphine), which gives it a sense of independence and confidence, and facilitates the work of nurses. This methodology is characterized by high efficiency and relative safety. According to this previously mentioned large British study, the frequency of reducing the saturation of capillary blood oxygen during KPVA IRS was 11.5%, while their intramuscular injection - 37% (Dolin S., Cashman J., 2002). Prospects for patient-controlled opioid analgesics usage in our country are limited accounting problems and cheating of opioid analgesics.
    Traditionally, systemic administration of opioids was considered as a basis for postoperative analgesia. At the same time, the effectiveness of pain management in the traditional appointment of opioids as a monotherapy does not exceed 25-30%. The problem is that an effective analgesic dose is often close to that cause depression of respiration.
   The appointment of postoperative opioid analgesics is associated with an increase in the number of postoperative complications and increases the cost of the patient's stay in the clinic.