Narcotic painkillers (also called opioid analgesics) are centrally acting drugs used to relieve pain syndrome of moderate to severe intensity.
Drugs of a group of morphine and its derivatives of alkaloids (opioid analgesics), as well as synthetic opioids belong to narcotic painkillers.
The mechanism of action of narcotic painkillers is well studied. Opioids interact with one or more subtypes of opioid receptors located in the CNS and peripheral tissues.
As a result of interaction of opioid analgesics with mu, delta and kappa receptors at supraspinal, spinal and peripheral levels, transmission of pain impulses is disrupted and pain syndrome is arrested.
Indications for narcotic painkillers use are:
- anesthesia during childbirth;
- pain relief in cancer patients;
- relief of pain syndrome in postoperative period;
- pain relief after physical trauma (factory accident);
In addition, narcotic painkillers can be prescribed to relieve pain in an attack of renal colic or as an antitussive agent in severe bronchitis and whooping cough.
When treating chronic non-oncologic pain, a wide use of narcotic painkillers is contributed by the following factors:
Use of narcotic painkillers is contraindicated if the patient suffers from breathing and circulatory disorders, increased intracranial pressure, and severe renal and hepatic insufficiency.
By severity of provided analgesic effect, narcotic painkillers are conditionally divided into two groups:
The group of weak opioids includes Codeine, Dihydrocodeine, Hydrocodone, Tramadol and Propoxyphene. These narcotic painkillers have a short analgesic effect and can be used in combination with non-narcotic analgesics, such as acetylsalicylic acid or paracetamol.
Weak opioids are used to relieve mild to moderate pain. The main medicinal forms of weak opioids are:
- oral tablets and capsules
- oral solution and syrup
Strong opioids are characterized by strong analgesic activity. These narcotic painkillers are used to relieve severe chronic pain syndrome of different genesis.
The strong opioids group includes buprenorphine, methadone, morphine, oxycodone, hydromorphone, and fentanyl. The main dosage forms of these narcotic painkillers are:
- sublingual and nasal spray;
- sublingual and buccal tablets;
- oral capsules and tablets;
- solution for intravenous, epidural, intrathecal use;
- transdermal therapeutic system (pain relief patch);
Choice of a narcotic painkiller should be determined by a number of factors, the main ones are etiology, intensity and type of pain. It is also should be taken into account the patient's age and individual characteristics.
Effectiveness of anesthesia depends not only by the analgesic itself, but also by route of its administration. Narcotic painkillers should be administered by the most effective, convenient and least painful way.
Parenteral administration of narcotic painkillers can be an effective way to achieve the required level of analgesia in patients who cannot get the desired effect by oral or transdermal route of analgesic administration.
Subcutaneous and intramuscular are the main parenteral routes of administration of narcotic painkillers. In those cases when it is necessary to quickly stop pain syndrome, intravenous route of analgesic administration is used.
Spinal administration of narcotic painkillers (epidural and intrathecal) is used in some patients in the presence of intense pain. During spinal administration, opioid analgesics quickly relieve pain causing minimal side effects.
One of the conditions for effective analgesia is adequacy of a dose. When carrying out analgesic therapy, a dose of narcotic painkillers is selected depending on the specific situation.
Doses of analgesics are selected beginning with high doses of weak drugs to low doses of strong analgesics. If the maximum doses of weak opioids cease to be effective, but pain gradually increases, weak opioid should be replaced with a strong opioid.
Despite high effectiveness, narcotic painkillers have an ability to cause side effects. Typically, these adverse reactions depend on the dose taken and duration of using analgesic.
In prolonged use, the patient may develop constipation. Therefore, patients receiving strong opioids, laxatives are often prescribed for prophylactic purpose.
A typical consequence of the initial administration of narcotic painkillers is vomiting and nausea. In prolonged administration of opioids, activity of vomiting center is suppressed and these undesirable effects pass.
One of the problems associated with long-term use of narcotic painkillers is tolerance development and analgesic dependence. Tolerance is expressed by the body’s resistance to opioid analgesia.
Reason for this condition is habituation of opioid receptors to the applied painkiller dose that requires a gradual increase of the analgesic dose.
Dependence on narcotic painkillers can be formed at different terms and withdrawal syndrome is manifested in sharp discontinuation of pain reliever intake.
Withdrawal syndrome is characterized by a particular irritability, sweating, nausea, vomiting, and insomnia. To avoid development of this syndrome, a dose of narcotic painkillers should be gradually reduced within 2-3 weeks.
Accurate adherence to the recommendations of sequence of prescribing narcotic painkillers and careful dose-selection allows to conduct effective treatment of chronic pain, both oncological and non-oncological genesis.