2). Narcotic (opioid) analgesics. Classification. Mechanism of action. Side effects. Contraindications Comparative evaluation of drugs. Antagonists of narcotic analgesics.

CLASSIFICATION OF NARCOTIC (OPIOID) ANALGESTS BY ORIGIN

1. Plant origin

Herbal preparations:Opium tincture and extract

Novogalenic drugs:Omnopon (contains 5 opium alkaloids)

Opium alkaloids:Morphine, Codeine

2. Synthetic morphine substitutes

Promedol, fentanyl, sufentanil, alfentanil, methadone, pentazocine, nalbuphine, butorphanol, buprenorphine, tramadol, etc.

CLASSIFICATION BY TYPE OF ACTION ON OPIOID RECEPTORS

Agonists - stimulate all types of opioid receptors (μ> κ = δ).

Antagonist agonists and partial agonists - simultaneously stimulate one type of opioid receptor and block others.

Opioid receptor antagonists - block receptors.

MECHANISMS OF ANALGESIC ACTION OF NARCOTIC ANALGETICS

1. Inhibition of the conduction of pain impulses in the afferent pathways of the central nervous system (impaired transmission of impulses from the endings of the primary afferents to the intercalary neurons of the spinal cord).

2. Strengthening the inhibitory effect of the descending antinociceptive system on the conduction of pain impulses in the afferent pathways of the central nervous system.

3. Change in emotional assessment of pain.

SIDE EFFECTS

1. Nausea, vomiting.

2. Respiratory depression.

3. Bradycardia.

4. Intestinal colic, constipation.

5. Arterial hypotension.

6. With repeated use - addiction, drug dependence.

7. Retention of urination.

8. Increased intracranial pressure.

CONTRAINDICATIONS

1. Children under 1 year of age (morphine - for children under 3).

2. Severe exhaustion.

3. Respiratory failure.

4. Traumatic brain injury (risk of cerebral edema).

5. Paralytic, spastic and obstructive gastrointestinal diseases.

6. Hypertrophy of the prostate

7. Intracranial hypertension.

8. Pregnancy.

9. Fentanyl is contraindicated: during caesarean section (before fetal extraction) and other obstetric manipulations, severe hypertension in the pulmonary circulation, pneumonia, atelectasis, pulmonary infarction, bronchial asthma, parkinsonism (increases muscle stiffness).

10. Butorphanol and pentazocine are not prescribed for patients with coronary artery disease and heart failure.

Comparative characteristics of drugs.

Morphine - acts on the central nervous system, depresses the respiratory center, does not disturb the ventilation of the lungs, depresses the cough center, the vomiting center, stimulates the center of the vagus (bradycardia), increases the tone of smooth muscles, reduces intestinal secretion and diuresis, reduces the basal metabolism, causes hyperglycemia, lowers body temperature.

Promedol weaker than morphine in analgesic effect, less inhibits the respiratory center, does not affect uterine contractions during childbirth, does not spasm smooth muscles, acts for 3-4 hours.

Fentanyl - 100 times more active than morphine in terms of analgesic effect, inhibits the respiratory center, pain relief after 1-3 minutes for 30 minutes, is used for neuraleptanalgesia.

ANAGONISTS OF NARCOTIC ANALGETICS

Agonist antagonists - nalorphine (blocks μ- and stimulates κ- and δ-receptors)

Antagonists - naloxone, naltrexone (block all types of opioid receptors).

In case of poisoning with narcotic analgesics, respiratory depression is eliminated, all systemic effects of opioid analgesics, including euphoria, are eliminated, causing withdrawal symptoms in drug addicts.

Naloxone lasts for about 1-3 hours, and it must be re-injected, since narcotic analgesics work for a long time. Administered intravenously or intramuscularly. When administered intravenously, it normalizes breathing in 1-2 minutes. In addition, the drug is used for alcoholic coma, shock conditions, and some mental illnesses.

Naltrexone acts like naloxone, but for a longer period - up to 24-40 hours, is used orally, in tablets, the effect occurs after 1-2 hours.

Nalorphine is rarely used in case of an overdose of narcotic analgesics.