Usage
- Mepacrine, an antimalarial drug, is primarily prescribed for the treatment of malaria. It also finds use in treating giardiasis (a parasitic intestinal infection) and lupus erythematosus (an autoimmune disease affecting the skin, joints, and internal organs), particularly discoid and subacute cutaneous lupus erythematosus. Additionally, it is used for other dermatological conditions like erythema multiforme, sarcoidosis, and dermatomyositis.
- Pharmacological Classification: Antimalarial, anti-inflammatory, antiparasitic.
- Mechanism of Action: Mepacrine inhibits DNA and RNA synthesis in susceptible organisms. It binds to DNA, interfering with the replication and transcription processes. This action is particularly effective against Plasmodium species (malaria parasites) and Giardia lamblia (causing giardiasis). Its anti-inflammatory mechanism in lupus is not completely understood, but it is believed to involve inhibition of phospholipase A2.
Alternate Names
How It Works
- Pharmacodynamics: Mepacrine exerts its effect by interfering with DNA replication and transcription, thus inhibiting parasitic growth and reproduction. In lupus, it reduces inflammation, though the exact mechanism remains partially unclear.
- Pharmacokinetics:
- Absorption: Mepacrine is rapidly absorbed from the gastrointestinal tract.
- Distribution: It is widely distributed throughout the body, accumulating in tissues, especially the liver.
- Metabolism: Mepacrine is slowly metabolized in the liver.
- Elimination: It is excreted slowly, primarily in urine, with traces found in bile, sweat, and saliva. Detection in urine is possible even months after discontinuation.
- Mode of Action: Mepacrine binds to DNA, inhibiting RNA and DNA polymerase, thereby disrupting protein synthesis and ultimately leading to parasitic death.
- Receptor Binding/Enzyme Inhibition: Binds to DNA and inhibits DNA/RNA polymerase, also inhibiting phospholipase A2, contributing to its anti-inflammatory effects.
- Elimination Pathways: Primarily renal excretion, also through feces, with some elimination via bile, sweat, and saliva.
Dosage
Standard Dosage
Adults:
- Malaria: 200 mg every six hours for five doses, followed by 100 mg every eight hours for six days (half dosage for patients under 50 kg).
- Giardiasis: 100 mg three times a day for 5-7 days.
- Lupus Erythematosus: 50 mg three times a week up to 100 mg three times daily.
Children:
- Malaria: Half the adult dose for those under 50kg
- Giardiasis: 2 mg/kg three times a day for 5-7 days (maximum 300 mg daily).
- Lupus Erythematosus: 2 mg/kg/day in three divided doses (maximum 300 mg daily).
Special Cases:
- Elderly Patients: Use with caution due to potential for increased side effects. Dose adjustment may be required.
- Patients with Renal Impairment: Caution is advised; dose adjustment may be necessary.
- Patients with Hepatic Dysfunction: Use with caution; dose adjustment may be necessary due to mepacrine’s hepatic metabolism.
- Patients with Comorbid Conditions: Caution is advised, especially in patients with psychiatric history, psoriasis, or myasthenia gravis.
Clinical Use Cases
Dosage recommendations for clinical situations like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations are not specifically available in the provided sources.
Dosage Adjustments
Dosage adjustments should be made for patients with hepatic or renal impairment, elderly patients, and those with comorbid conditions as advised by the physician.
Side Effects
Common Side Effects
- Nausea, vomiting, diarrhea
- Dizziness, headache
- Yellow discoloration of skin and urine (reversible)
- Blue-black discoloration of palate and nails (reversible)
Rare but Serious Side Effects
- Liver toxicity
- Severe skin reactions
- Hemolytic anemia
- Psychosis, CNS stimulation, convulsions
- Aplastic anemia
Long-Term Effects
Long-term effects might include liver damage, skin discoloration, and neurological issues. Regular monitoring is recommended for patients on prolonged therapy.
Adverse Drug Reactions (ADR)
Severe skin reactions, hepatotoxicity, blood disorders like aplastic anemia and hemolytic anemia require immediate attention.
Contraindications
- Hypersensitivity to mepacrine
- Psoriasis
- Myasthenia gravis
- History of psychosis
Drug Interactions
- Antacids (reduce mepacrine absorption)
- Primaquine (increased risk of primaquine toxicity)
- Alcohol (disulfiram-like reaction)
- Other antimalarials (increased toxicity risk)
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Data insufficient. Use only if clearly needed and benefits outweigh potential risks.
- Breastfeeding: Data insufficient. Avoid use or discontinue breastfeeding.
Drug Profile Summary
- Mechanism of Action: Inhibits DNA/RNA synthesis, also has anti-inflammatory properties.
- Side Effects: Nausea, vomiting, dizziness, headache, skin/urine discoloration (reversible), and rarely, serious reactions like liver toxicity and blood disorders.
- Contraindications: Hypersensitivity, psoriasis, myasthenia gravis, history of psychosis.
- Drug Interactions: Antacids, primaquine, alcohol, other antimalarials.
- Pregnancy & Breastfeeding: Insufficient data; generally avoided.
- Dosage: Varies based on indication and patient factors (see Dosage section).
- Monitoring Parameters: Liver function tests, blood counts (especially during long-term use).
Popular Combinations
Mepacrine is often used in combination with hydroxychloroquine for the treatment of lupus erythematosus, especially skin manifestations, due to their synergistic effects.
Precautions
- Pre-existing medical conditions like liver disease, porphyria, and history of psychosis.
- Elderly patients.
- Alcohol consumption should be avoided.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Mepacrine?
A: Dosage varies depending on the condition being treated. Refer to the detailed Dosage section above.
Q2: What are the common side effects of Mepacrine?
A: Common side effects include nausea, vomiting, diarrhea, dizziness, headache, and reversible yellowing of skin and urine.
Q3: Is Mepacrine safe during pregnancy and breastfeeding?
A: There’s insufficient data on Mepacrine’s safety during pregnancy and breastfeeding. It’s generally recommended to avoid its use.
Q4: What are the contraindications for Mepacrine?
A: Mepacrine is contraindicated in patients with hypersensitivity, psoriasis, myasthenia gravis, and a history of psychosis.
Q5: Does Mepacrine interact with other medications?
A: Yes, Mepacrine interacts with antacids, primaquine, alcohol, and other antimalarials.
Q6: What is the mechanism of action of Mepacrine?
A: Mepacrine inhibits DNA/RNA synthesis and has anti-inflammatory properties.
Q7: What precautions should be taken while prescribing Mepacrine?
A: Caution should be exercised in patients with pre-existing liver disease, porphyria, history of psychosis, and in elderly patients. Alcohol consumption should be avoided.
Q8: What are the long-term effects of Mepacrine?
A: Long-term effects can include liver damage, skin discoloration, and neurological issues. Regular monitoring is recommended for patients on prolonged therapy.
Q9: What should be done in case of Mepacrine overdose?
A: In case of overdose, supportive and symptomatic treatment should be provided, including gastric lavage or inducing emesis if appropriate. Monitor vital signs and provide appropriate medical care.
