Basic measures and non-pharmacological care
When renal colic develops, the primary task is to relieve acute pain, which is most often caused by severe spasm. As first aid, thermal procedures are used. The patient is prescribed a warm bath or a heating pad is applied. Local application of heat promotes relaxation of the smooth muscles of the urinary tract and partial relief of spasm, which facilitates the patient's condition before the start of active pharmacotherapy.
Pharmacotherapy and selection of an opioid analgesic
Drug treatment is based on the intravenous administration of painkillers and antispasmodics. In case of severe pain syndrome that is not relieved by standard drugs, narcotic analgesics are used.
It is important to choose the drug wisely. A typical full opioid receptor agonist — morphine — provides powerful analgesia while maintaining consciousness. However, its use in colic is limited, as pure morphine can enhance smooth muscle spasm.
The drug of choice in this situation is omnopon. This is a combined agent representing a mixture of opium alkaloids. It includes phenanthrene alkaloids (about 48–50% morphine, as well as codeine and thebaine) and isoquinoline alkaloids (noscapine and papaverine). It is the presence of papaverine that provides a pronounced antispasmodic effect. Omnopon is administered parenterally (subcutaneously or intravenously) and is ideal for relieving pain caused by spasms in renal, hepatic, or intestinal colic.
Alternative analgesics in emergency care
If the pain is resistant to standard opioids or there are contraindications, other drugs may be used:
- Fentanyl is a phenylpiperidine derivative, a full μ-receptor agonist. It is 100–400 times more potent than morphine and is capable of relieving the most severe pain. It is available as a colorless liquid and causes deep analgesia. It is metabolized in the liver and excreted in the urine. It requires caution due to the risk of bradycardia, bronchospasm, ataxia, and respiratory depression.
- Tramadol is an analgesic with a mixed mechanism. It combines opioid action (non-selective μ-, δ-, and κ-receptor agonist) and non-opioid action (disrupts neuronal reuptake of serotonin and noradrenaline, enhancing inhibitory effects on pain transmission in the spinal cord). Tramadol is inferior to morphine in potency, but has huge advantages: it does not increase urinary tract tone, practically does not depress respiration, does not reduce gastrointestinal motility, lacks ulzerogenic effects, and is approved for patients with high cardiovascular risk.
- Butorphanol is an opioid receptor agonist-antagonist. It suppresses the respiratory center to a lesser extent compared to morphine and has less pronounced side effects.
- Buprenorphine is a partial μ-receptor agonist. Its activity is 20–30 times higher than that of morphine, and the effect lasts up to 8–12 hours when administered sublingually. Due to its prolonged anti-shock effect, it is especially convenient for emergency care in mass casualties and patient transportation.
Although codeine also belongs to narcotic analgesics, its analgesic activity is 10 times weaker than morphine. It suppresses the cough center more strongly and is used mainly as an antitussive agent.
Side effects and signs of opioid intoxication
When using narcotic analgesics, the doctor must strictly monitor the patient's condition. Opioids have a number of central effects:
- Psychotropic effect: development of euphoria, elimination of fear and emotional tension.
- Effect on the brainstem: stimulation of the trigger zone of the vomiting center leads to nausea and vomiting.
- Sedative and antidiarrheal effects.
- Effect on the cardiovascular system: development of bradycardia (characteristic of morphine).
The key diagnostic signs of opioid overdose and intoxication are two symptoms: miosis (pronounced pupil constriction due to stimulation of the oculomotor nerve nuclei) and bradypnea (a consequence of direct depression of the respiratory center). It is worth noting that opioids as a group do not possess a hallucinogenic effect.
For quick memorization of the main signs of opioid intoxication, use the rule of two "C"s (in Russian: Suzheniye zrachkov for miosis and Snizheniye chastoty dykhaniya for decreased respiratory rate).
Class and exam questions
Why is it preferable to use omnopon rather than morphine for renal colic?
Omnopon contains papaverine, which provides the necessary antispasmodic effect. Pure morphine, on the contrary, can enhance smooth muscle spasm, which can worsen the patient's condition.
What symptoms indicate an overdose of narcotic analgesics?
Characteristic diagnostic signs of opioid intoxication are pronounced pupil constriction (miosis) and slow breathing resulting from depression of the respiratory center.
What is the advantage of tramadol in relieving pain syndrome?
Tramadol practically does not depress respiration, does not increase urinary tract tone, and does not reduce GI motility. In addition, it has a significantly lower abuse potential compared to classical opioids.
What else to study on this topic
- Mechanism of action of tramadol: combination of opioid and monoaminergic components.
- Spectrum of central effects of morphine and its impact on brainstem centers.
- Pharmacological profile of fentanyl and its use in anesthesiological practice.
- Features of buprenorphine use in emergency care during mass casualties.
- Differences between full agonists, partial agonists, and opioid receptor agonists-antagonists.
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