dirithromycin

Action and Spectrum

Actions and spectrum: 

• Mechanism of Action: Dirithromycin inhibits bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome. This action prevents the elongation of the growing peptide chain during translation, leading to the inhibition of bacterial protein synthesis. 

Spectrum of Activity: 

• Gram-Positive Bacteria: Dirithromycin is effective against a broad spectrum of gram-positive bacteria, including Streptococcus pneumoniae, Streptococcus pyogenes (Group A Streptococcus), Staphylococcus aureus (including some methicillin-resistant strains), and others. 
• Gram-Negative Bacteria: While macrolides like dirithromycin are generally less effective against gram-negative bacteria, they may still have activity against some strains of Haemophilus influenzae and Moraxella catarrhalis. 
• Atypical Bacteria: Macrolides, including dirithromycin, are known for their activity against atypical bacteria such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila. 

Drug Interaction

Adverse Reaction

Frequency not defined 

GI disturbances

hearing loss 

CV effects 

Stevens-Johnson syndrome 

hypersensitivity reactions 

cholestatic jaundice 

myasthenia-like syndrome 

toxic epidermal necrolysis 

Black Box Warning

Black Box Warning: 

there were no specific black box warnings associated with dirithromycin. 

Contraindication / Caution

Contraindication/Caution: 

Contraindication: 

• Hypersensitivity: Contraindicated in individuals with a known hypersensitivity or allergic reaction to dirithromycin or any other macrolide antibiotics. 
• Concomitant Use with Ergotamine or Dihydroergotamine: Macrolide antibiotics, including dirithromycin, may interact with ergot alkaloids such as ergotamine and dihydroergotamine, leading to an increased risk of ergot toxicity. Therefore, their concomitant use is contraindicated. 
• Myasthenia Gravis: Use with caution or avoid in individuals with a history of myasthenia gravis, as macrolide antibiotics may exacerbate muscle weakness in these patients. 
• Kidney Dysfunction: While macrolides are considered safe in patients with kidney impairment, dosage adjustments may be required in individuals with severe renal dysfunction.

Caution: 

• Hypersensitivity Reactions: Macrolide antibiotics, including dirithromycin, can cause hypersensitivity reactions. Individuals with a history of allergic reactions to macrolides should exercise caution, and alternative antibiotics may be considered. 
• Gastrointestinal Effects: Macrolide antibiotics are known to cause gastrointestinal side effects like nausea, vomiting, abdominal pain, and diarrhea. If severe or persistent, individuals should seek medical attention. 
• Use in Myasthenia Gravis: Macrolide antibiotics may exacerbate muscle weakness in individuals with myasthenia gravis. Caution is advised, and the drug should be used with care in these patients. 
• Liver Function: Although severe liver toxicity is rare with macrolides, caution is recommended in individuals with preexisting liver dysfunction. Liver function tests may be monitored in certain cases.

Comorbidities: 

• Hepatic Impairment: Dirithromycin is metabolized in the liver, so individuals with preexisting liver conditions may require cautious use. In severe cases of hepatic impairment, alternative antibiotics or dosage adjustments might be considered. 
• Cardiovascular Conditions: Individuals with a history of cardiovascular conditions, especially those prone to QT interval prolongation, may require careful monitoring when prescribed dirithromycin, as macrolide antibiotics have been associated with this cardiac effect. 
• Myasthenia Gravis: Patients with myasthenia gravis may experience exacerbation of muscle weakness when using macrolide antibiotics, including dirithromycin. Caution and close monitoring are advised. 
• Allergies or Hypersensitivity Reactions: Individuals with a history of allergies or hypersensitivity to macrolide antibiotics should exercise caution when using dirithromycin, as they may have an increased risk of adverse reactions. 

Pregnancy / Lactation

Pregnancy consideration: pregnancy category: not assigned 

Lactation: excreted into human milk: unknown  

Pregnancy category: 

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 
• Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.   
• Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women. 
• Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

Dirithromycin, a macrolide antibiotic, exerts its pharmacological effects by inhibiting bacterial protein synthesis. Like other macrolides, dirithromycin binds to the 50S subunit of ribosome, preventing the elongation of the nascent peptide chain during translation. By interfering with this essential process, dirithromycin disrupts bacterial protein synthesis, leading to inhibition of bacterial growth and multiplication.

The drug acts against gram-positive bacteria, including Streptococcus pneumoniae and Staphylococcus aureus. While macrolides are less effective against gram-negative bacteria, dirithromycin may exhibit activity against some strains of Haemophilus influenzae and Moraxella catarrhalis.

Dirithromycin is commonly used to treat respiratory tract infections, including community-acquired pneumonia and acute bacterial exacerbations of chronic bronchitis, and its effectiveness extends to certain skin and soft tissue infections.

As with all antibiotics, the appropriate use of dirithromycin involves consideration of the specific bacterial pathogen, local resistance patterns, and individual patient factors.  

Pharmacodynamics: 

• Inhibition of Protein Synthesis: Dirithromycin interferes with bacterial protein synthesis by binding to 50S ribosome. By binding to the ribosome, dirithromycin prevents the elongation of the polypeptide chain during translation, inhibiting the synthesis of bacterial proteins. 
• Bacteriostatic Action: Dirithromycin exhibits bacteriostatic action, meaning it inhibits the growth and multiplication of bacteria rather than directly causing bacterial cell death (bactericidal action). This bacteriostatic effect allows the host’s immune system to better combat the inhibited bacteria. 
• Broad Spectrum of Activity: Dirithromycin has a broad spectrum of activity, primarily against gram-positive bacteria. It is effective against various gram-positive pathogens, including Streptococcus pneumoniae, Streptococcus pyogenes (Group A Streptococcus), and Staphylococcus aureus (including some methicillin-resistant strains). 
• Treatment of Respiratory Infections: Dirithromycin is commonly used to treat respiratory tract infections, such as community-acquired pneumonia, chronic bronchitis, and pharyngitis/tonsillitis. 

Pharmacokinetics: 

• Absorption: Dirithromycin is administered orally, and absorption occurs in the gastrointestinal tract. It is a prodrug that undergoes hydrolysis to its active form, erythromycylamine, in the gastrointestinal tract. 
• Distribution: Dirithromycin, once absorbed, is distributed throughout the body via the bloodstream. The drug can penetrate various tissues, allowing it to reach the site of infection. 
• Metabolism: dirithromycin is a prodrug, and its conversion to erythromycylamine involves hydrolysis in the gastrointestinal tract. The active form of the drug, erythromycylamine, is then further metabolized in the liver. 
• Excretion: The primary route of excretion for dirithromycin and its metabolites is through the bile. Some portion of the drug may undergo renal excretion, but the majority is eliminated through the feces. The elimination half-life of dirithromycin can vary, but it is around 4 to 5 hours. 

Adminstartion

Administration: 

• Oral Administration: Dirithromycin is administered orally, and the tablets or capsules are usually taken with a full glass of water. It can be taken with or without food, depending on the healthcare provider’s instructions. 
• Dosage: The dosage of dirithromycin varies depending on type and severity of infection being treated. 
• Timing and Frequency: The dosing frequency and timing of dirithromycin administration depend on the specific formulation prescribed and the healthcare provider’s instructions. It is important to adhere to the recommended dosing schedule to maintain effective drug levels in the body. 
• Duration of Treatment: The duration of dirithromycin treatment is based on type of infection and the healthcare provider’s assessment of the patient’s response to therapy. Patients should complete the entire course of treatment, even if symptoms improve before completion. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: dirithromycin 

Pronounced: (di-rih-throh-MY-sin)  

Why do we use dirithromycin? 

Dirithromycin is a macrolide antibiotic used to treat various bacterial infections. Its spectrum of activity includes both gram-positive and some gram-negative bacteria. Dirithromycin is often prescribed for respiratory tract infections, including community-acquired pneumonia. It may also be used in the treatment of acute bacterial exacerbations of chronic bronchitis.

Dirithromycin may be used in the treatment of pharyngitis and tonsillitis caused by susceptible bacteria, especially in cases where penicillin is not an option. In some cases, dirithromycin may be indicated for skin and soft tissue infections. Dirithromycin might be considered in the treatment of certain genitourinary tract infections, depending on the causative bacteria and susceptibility patterns.