Usage
- Phenyramidol is prescribed for the relief of mild to moderate acute pain associated with musculoskeletal disorders such as lumbago (lower back pain), integumental pain (skin pain), and other musculoskeletal pain conditions, including neck and shoulder pain and pain associated with muscle spasms (e.g., from strains or sprains). It is often recommended to combine this medication with rest and physical therapy.
- Pharmacological Classification: Skeletal muscle relaxant, analgesic.
- Mechanism of Action: Phenyramidol primarily works by inhibiting polysynaptic reflexes within the brain and spinal cord, thus disrupting the transmission of pain signals from the nerves to the brain. This action helps to alleviate muscle stiffness and spasms, consequently improving muscle strength. It may also modulate the effects of certain neurotransmitters in the central nervous system like serotonin, norepinephrine, GABA, and glycine, further contributing to muscle relaxation.
Alternate Names
- INN: Fenyramidol
- Brand Names: Cabral, Realflex
How It Works
- Pharmacodynamics: Phenyramidol acts centrally to reduce the excitability of motor neurons, primarily in the spinal cord and brainstem. This leads to muscle relaxation and a reduction in painful muscle contractions and spasms. The drug’s analgesic effect stems from its interference with pain signal transmission in the central nervous system.
- Pharmacokinetics: Phenyramidol is administered orally and is well-absorbed from the gastrointestinal tract. Its metabolism and elimination pathways are not extensively documented in the provided literature. However, one source mentions hepatic metabolism as a possible pathway. It is known to inhibit the metabolism of certain drugs, including phenytoin, tolbutamide, bishydroxycoumarin, zoxazolamine, and pentobarbital. This can lead to elevated plasma concentrations of these co-administered drugs, potentially increasing the risk of adverse effects.
Dosage
Standard Dosage
Adults:
- The typical adult dosage is 400 mg (one to two tablets) taken two to three times a day, preferably after meals.
- Treatment duration is generally 3 to 7 days, depending on the severity of the condition.
- Maximum daily dose should not exceed 3200 mg.
Children:
- Phenyramidol is not recommended for use in children under 16 years of age due to insufficient safety and efficacy data.
Special Cases:
- Elderly Patients: Initiate treatment with a lower dose and adjust as needed based on clinical response and tolerability. Closely consider comorbidities and potential drug interactions.
- Patients with Renal Impairment: Use cautiously and monitor renal function. Dosage adjustments might be necessary.
- Patients with Hepatic Dysfunction: Administer with caution. Monitor liver function tests, especially liver enzymes. Dosage adjustments might be required.
- Patients with Comorbid Conditions: Exercise caution in patients with diabetes, those taking anticoagulants (like warfarin), or anticonvulsants due to possible drug interactions. Monitor blood glucose, INR, and plasma levels of the interacting drugs as appropriate.
Clinical Use Cases
Phenyramidol is primarily used for acute musculoskeletal pain management. It is not typically utilized in settings like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations.
Dosage Adjustments
Dose modifications are necessary based on patient-specific factors such as renal or hepatic dysfunction.
Side Effects
Common Side Effects:
- Drowsiness
- Dizziness
- Nausea
- Dry mouth
- Headache
- Gastrointestinal discomfort (constipation, gastric irritation)
- Itching
- Skin rash
Rare but Serious Side Effects:
- Hepatotoxicity (liver damage)
Long-Term Effects:
Chronic complications from prolonged use are not well-documented.
Adverse Drug Reactions (ADR):
- Clinically significant ADRs include hepatotoxicity.
Contraindications
- Hypersensitivity to phenyramidol
- Severe liver or kidney disease
Drug Interactions
- Phenyramidol can interact with various medications, including:
- Pain killers (pentazocine, buprenorphine, nalbuphine)
- Blood thinners (warfarin)
- Anti-anxiety drugs (alprazolam)
- Anticonvulsants (carbamazepine, phenytoin)
- Antiemetics (ondansetron)
- Antifungals (ketoconazole)
- Antibiotics (ciprofloxacin, erythromycin)
- Anticancer drugs (ceritinib, lapatinib)
- Antidiabetic drugs (tolbutamide)
- CYP450 Interactions: Phenyramidol inhibits the metabolism of certain drugs metabolized by CYP450 enzymes.
- Other Interactions:
- Grapefruit juice: Avoid concomitant use, as it can increase phenyramidol levels.
- Alcohol: Avoid concurrent consumption due to increased risk of drowsiness, dizziness, and potentially stomach bleeding.
Pregnancy and Breastfeeding
- Pregnancy: Limited data are available. Use with caution if potential benefits outweigh the risks. It has been considered highly unsafe in some sources.
- Breastfeeding: Limited data are available. Potential for neonatal exposure. Use with caution if benefits outweigh the risks to the infant.
Drug Profile Summary
- Mechanism of Action: Inhibits polysynaptic reflexes in the CNS, leading to muscle relaxation and analgesia.
- Side Effects: Drowsiness, dizziness, nausea, dry mouth, headache, gastrointestinal upset, hepatotoxicity (rare).
- Contraindications: Hypersensitivity to phenyramidol, severe liver/kidney disease.
- Drug Interactions: Anticoagulants, antidiabetics, anticonvulsants, CNS depressants, grapefruit juice, alcohol.
- Pregnancy & Breastfeeding: Use cautiously, weighing benefits against potential risks.
- Dosage: Adults: 400 mg 1-2 tablets, 2-3 times/day. Children: Not recommended under 16 years of age.
- Monitoring Parameters: Liver function tests, blood glucose (in diabetics), INR (in patients on warfarin), plasma levels of concomitant anticonvulsants.
Popular Combinations
No consistently documented “popular” drug combinations with phenyramidol are clinically recommended. Combining phenyramidol with other drugs should be done cautiously due to potential drug interactions.
Precautions
- General Precautions: Screen for allergies, metabolic disorders, and organ dysfunction. Caution is advised in patients with a history of drug dependency.
- Specific Populations: As described above in special cases for dosage.
- Lifestyle Considerations: Avoid alcohol and operate machinery with caution due to the risk of drowsiness and dizziness.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Phenyramidol?
A: The standard adult dosage is 400 mg (one to two tablets), taken two or three times a day, preferably after meals. The maximum daily dose is 3200 mg. Phenyramidol is not recommended for children under 16.
Q2: What are the common side effects of Phenyramidol?
A: Common side effects include drowsiness, dizziness, nausea, dry mouth, headache, and gastrointestinal issues like constipation or gastric irritation.
Q3: Are there any serious side effects to be aware of?
A: Although rare, hepatotoxicity (liver damage) has been reported. Monitor liver function, especially in patients with pre-existing liver conditions.
Q4: Can Phenyramidol be used during pregnancy or breastfeeding?
A: Limited data are available regarding the use of phenyramidol during pregnancy and breastfeeding. Use with caution only if the potential benefits outweigh the risks to the fetus or infant. Consult a specialist for guidance.
Q5: Does Phenyramidol interact with other medications?
A: Yes, Phenyramidol can interact with numerous medications, including anticoagulants, antidiabetics, and anticonvulsants. It also interacts with alcohol and grapefruit juice. Provide a complete medication history to assess potential interactions.
Q6: What is the mechanism of action of Phenyramidol?
A: Phenyramidol works by inhibiting polysynaptic reflexes in the central nervous system, thereby reducing pain signal transmission and promoting muscle relaxation.
Q7: How long should a patient typically take Phenyramidol?
A: The usual treatment duration is 3 to 7 days, depending on the severity of the condition.
Q8: Can Phenyramidol be used in patients with kidney or liver problems?
A: Phenyramidol should be used cautiously in patients with renal or hepatic impairment. Careful monitoring and dose adjustments might be necessary.
Q9: What should patients do if they miss a dose of Phenyramidol?
A: Take the missed dose as soon as remembered. If it is almost time for the next dose, skip the missed dose and continue with the regular schedule. Do not double the dose.
