Retapex

A. Approved Indications

• Impetigo caused by Staphylococcus aureus or Streptococcus pyogenes:
• Indicated for the topical treatment of impetigo in adults and pediatric patients aged 9 months and older.

B. Clinically Accepted Off-Label Uses

• Secondary skin infections (limited use):
• May be used in superficial traumatic lesions, abrasions, or minor lacerations when infected by susceptible organisms (off-label use; based on clinical experience).
• May be applied to localized infected dermatitis, but systemic signs of infection warrant oral/IV antibiotics.

A. Adults and Pediatric Patients (≥9 months):

• Apply a thin layer of Retapamulin 1% ointment to the affected area twice daily for 5 days.
• Area may be covered with a sterile bandage or left exposed, depending on the lesion.
• Reassess therapy if there is no improvement after 3–4 days of treatment.

B. Pediatric Use (<9 months):

• Not recommended due to insufficient safety data.

C. Renal or Hepatic Impairment:

• No dosage adjustment necessary, as systemic absorption is minimal.

D. Geriatric Use:

• No dose adjustment needed; use as in adults.

Route of Administration:

• Topical (external use only)

Important Notes:

• Avoid use in eyes, mouth, vagina, or intranasally.
• Wash hands before and after application.
• Do not apply over large body areas or under occlusive dressings unless directed.

Retapamulin is a semi-synthetic pleuromutilin antibacterial agent. It inhibits bacterial protein synthesis by selectively binding to the 50S ribosomal subunit at a unique site that overlaps the peptidyl transferase center and prevents proper positioning of tRNA. This disrupts peptide bond formation and protein chain elongation, resulting in bacteriostatic effects. Against susceptible organisms, it can also exert bactericidal action, especially S. aureus and S. pyogenes in skin infections. Its novel binding site ensures minimal cross-resistance with other antibiotic classes.

• Absorption:
• Systemic absorption is minimal (<2%) when applied to intact skin over limited areas.
• Absorption may increase with skin barrier disruption or large surface area application.
• Distribution:
• Due to minimal systemic absorption, plasma levels are generally undetectable or very low.
• Metabolism:
• Systemically absorbed retapamulin is metabolized in the liver, mainly by CYP3A4.
• Elimination:
• Primarily eliminated via hepatic metabolism and excreted in feces.
• Half-life:
• Not clinically significant due to low systemic exposure.

Pregnancy:

• FDA Pregnancy Category B
• Animal studies show no fetal harm, but there are no well-controlled studies in pregnant women.
• Use only if clearly needed.

Lactation:

• Unknown whether retapamulin is excreted into human breast milk.
• Systemic absorption is minimal, so risk to the breastfed infant is likely low, but caution is advised.
• Avoid applying to the nipple area if nursing.

• Class: Topical Antibacterial
• Subclass: Pleuromutilin derivative
• Category: Skin and soft tissue infection treatment (non-systemic)

• Known hypersensitivity to retapamulin or any component of the formulation
• Use in mucosal areas (e.g., eyes, mouth, vagina, or nose) is contraindicated
• Use in infants <9 months of age is not recommended due to lack of safety data

• Hypersensitivity reactions:
• Discontinue immediately if signs such as rash, hives, or angioedema appear
• Secondary infection or lack of improvement:
• If condition worsens or shows no improvement in 3–5 days, consider a superinfection or resistant organism, and switch to systemic therapy
• Not for intranasal use:
• Retapamulin is not effective against MRSA strains commonly colonizing the nares
• Avoid long-term or extensive use:
• Prolonged or extensive use may lead to resistance development

Common Adverse Effects (≥1%):

• Application site irritation (erythema, itching, burning)
• Headache (in pediatric patients)

Less Common/Rare:

• Allergic contact dermatitis
• Facial swelling or angioedema (rare, but serious)
• Secondary skin infection from resistant organisms
• Superficial fungal overgrowth in treatment area (with prolonged use)

Onset:

• Most reactions occur within first few days of treatment
• Reactions are generally mild and transient

• Systemic interactions are unlikely due to negligible absorption
• Retapamulin is a substrate of CYP3A4, so theoretical interactions exist with strong CYP3A4 inhibitors (e.g., ketoconazole), but are not clinically significant when used topically
• No known drug-food or drug-alcohol interactions

• EMA and FDA continue to support Retapamulin as a treatment option for impetigo, with clear labeling on:
• Age restrictions (≥9 months)
• Non-intranasal application
• Not recommended as first-line for MRSA-related impetigo due to resistance
• No recent additions to indication or major safety warnings in the past 3 years

• Storage Temperature:
• Store at 20°C to 25°C (68°F to 77°F)
• Allowable range: 15°C to 30°C (59°F to 86°F)
• Humidity & Light Protection:
• Protect from excessive moisture
• Store in the original tube with cap tightly closed
• Handling Instructions:
• Do not freeze
• Do not apply near eyes or mucous membranes
• Keep out of reach of children