Pirnuo

For the treatment of Impetigo and other Secondary Skin Infections, the standard adult dosage involves applying a small amount of mupirocin 2% ointment or cream to the affected area three times daily. This is typically continued for 5 to 10 days, depending on the severity of the infection and the clinical response. If no improvement is seen within 3 to 5 days, the patient should re-consult their healthcare provider.

For MRSA Nasal Decolonization, the nasal ointment (mupirocin calcium) is used. Approximately one-half of the ointment from a single-use tube (or a matchstick-sized amount) is applied into each nostril twice daily (morning and evening) for 5 days. After application, the nostrils should be pressed together and massaged to ensure even distribution of the medication.

Mupirocin is approved for use in pediatric patients. For Impetigo, the dosage for children aged 2 months to 16 years is the same as the adult dose: application to the affected area three times daily for 5 to 10 days. The safety and efficacy of the cream formulation have been established in children as young as 3 months for infected traumatic lesions.

For Nasal Decolonization, the nasal ointment is approved for use in children aged 12 years and older. Use in younger children for nasal decolonization must be strictly supervised and directed by a pediatric specialist.

Renal Impairment

No dosage adjustment is typically required for the cream or nasal ointment. However, caution is advised when using the topical ointment (which contains polyethylene glycol) over large areas of broken skin in patients with moderate to severe renal impairment, as PEG can be absorbed and cause kidney toxicity.

Hepatic Impairment

Since mupirocin is not significantly absorbed systemically, no dosage adjustments are required for patients with liver disease.

Elderly Patients

No specific dosage adjustments are recommended for geriatric patients, provided their skin integrity is relatively intact and renal function is monitored if large-scale application of the PEG-based ointment is required.

1. 1Preparation: Wash your hands thoroughly before and after application. Clean the affected skin area with mild soap and water and pat dry.
2. 2Application: Apply a thin layer of the ointment or cream to the lesion. You may use a cotton swab or gauze pad to avoid touching the infection directly.
3. 3Covering: The treated area may be covered with a sterile gauze dressing if desired or if the infection is in an area prone to friction.
4. 4Avoidance: Do not apply mupirocin to the eyes, mouth, or inside the nose (unless using the specific nasal formulation). If the medication gets into the eyes, rinse thoroughly with water.
5. 5Storage: Store the medication at room temperature (20°C to 25°C or 68°F to 77°F). Do not freeze.

If you miss a dose of mupirocin, apply it as soon as you remember. If it is almost time for your next scheduled application, skip the missed dose and return to your regular dosing schedule. Do not apply extra medication to 'make up' for a missed dose, as this may increase the risk of local irritation.

Systemic overdose via topical application is highly unlikely due to low absorption. However, if the medication is accidentally ingested, contact a poison control center or seek emergency medical attention immediately. Signs of ingestion might include nausea or gastrointestinal upset. If the PEG-based ointment is applied excessively to large open wounds in a patient with kidney issues, signs of renal distress (changes in urination, swelling) should be monitored.

> Important: Follow your healthcare provider's dosing instructions exactly. Even if the skin looks better, complete the full course of treatment to prevent the bacteria from returning or developing resistance.

Mupirocin is generally well-tolerated because it acts locally rather than systemically. The most common side effects are localized to the site of application. Approximately 1% to 3% of patients may experience:

• Burning or Stinging: A transient sensation of heat or sharp stinging immediately after application. This usually subsides within a few minutes.
• Pruritus (Itching): A mild to moderate urge to scratch the treated area. This is often a sign of local irritation rather than an allergy.
• Dryness: The skin at the application site may become slightly flaky or dry, particularly with the cream formulation.

Some patients may experience slightly more pronounced local reactions, including:

• Erythema (Redness): Visible reddening of the skin beyond the initial infection site.
• Contact Dermatitis: A localized inflammatory reaction that may include small bumps or a rash where the ointment was applied.
• Edema (Swelling): Minor localized swelling of the tissue surrounding the wound.
• Increased Exudate: A temporary increase in the amount of fluid draining from a treated wound.

Rarely, patients may experience systemic-like symptoms or severe local reactions:

• Abdominal Pain: Reported in very rare cases, though the causal link to topical mupirocin is weak.
• Dizziness: Extremely rare reports of lightheadedness.
• Secondary Infections: Prolonged use of mupirocin may result in the overgrowth of non-susceptible organisms, including fungi (yeast infections).

While rare, some side effects require immediate cessation of the drug and medical intervention.

> Warning: Stop taking Mupirocin and call your doctor immediately if you experience any of these:

• Anaphylaxis or Severe Hypersensitivity: Symptoms include hives, swelling of the face, lips, or tongue, difficulty breathing, or a widespread skin rash. This indicates a potentially life-threatening allergic reaction.
• Clostridioides difficile-Associated Diarrhea (CDAD): Although mupirocin is topical, any antibiotic can theoretically disrupt the body's bacterial balance. If you develop severe, watery, or bloody diarrhea (even months after treatment), contact your doctor immediately.
• Severe Local Irritation: If the burning, stinging, or itching becomes unbearable or if the skin begins to blister or peel excessively, the medication should be washed off and a provider consulted.
• Renal Toxicity (PEG-related): In patients with renal impairment using the ointment on large open wounds, signs of kidney strain like decreased urine output or fluid retention must be reported.

Mupirocin is not intended for long-term use. The primary risk of prolonged or repeated use is the development of bacterial resistance. Strains of S. aureus can develop 'high-level' mupirocin resistance (mupA gene), rendering the drug ineffective for future infections. Additionally, long-term use can lead to the overgrowth of fungi or other bacteria that do not respond to mupirocin, potentially leading to a more complicated secondary infection.

No FDA black box warnings are currently issued for Mupirocin. It is considered a safe medication when used as directed for the short-term treatment of localized skin infections.

Report any unusual symptoms to your healthcare provider to ensure your treatment plan remains safe and effective.

Mupirocin is for external use only. It should never be swallowed, injected, or applied to the eyes. If the medication is used on the face, care must be taken to avoid the conjunctiva (the lining of the eyelids). If accidental contact with the eyes occurs, they should be rinsed thoroughly with cool water. Furthermore, mupirocin should not be used for extended periods beyond what is prescribed, as this significantly increases the risk of developing antibiotic-resistant 'superbugs.'

No FDA black box warnings for Mupirocin. Unlike some systemic antibiotics that carry warnings for tendon rupture or severe nerve damage, mupirocin's localized application limits its systemic toxicity profile.

• Allergic Reactions / Anaphylaxis Risk: Patients with a known history of hypersensitivity to mupirocin or any components of the formulation (such as polyethylene glycol) must avoid this drug. A small 'test patch' is sometimes recommended if a patient has sensitive skin.
• Polyethylene Glycol (PEG) Toxicity: The mupirocin ointment base contains PEG. When PEG is absorbed through large areas of denuded skin (skin that has lost its top layer) or severe burns, it can cause metabolic acidosis and renal impairment. This is a critical concern for patients with pre-existing kidney disease.
• Mucosal Irritation: The standard topical ointment is not formulated for mucosal surfaces. Using it in the nose or mouth can cause severe stinging and irritation. Only the specific nasal ointment formulation should be used intranasally.
• Pseudomembranous Colitis: As with all antibiotics, there is a theoretical risk of C. difficile overgrowth. While the risk is extremely low for a topical product, patients should be aware of the symptoms of severe diarrhea.

For most patients using mupirocin for a short 5-day course, no specific laboratory monitoring is required. However, in specific clinical scenarios, healthcare providers may perform:

• Wound Cultures: To ensure the bacteria causing the infection are susceptible to mupirocin.
• Renal Function Tests (BUN/Creatinine): For patients with kidney disease who are applying the PEG-based ointment to large, open areas of skin.
• Skin Assessment: Regular monitoring of the site to ensure the infection is resolving and not showing signs of contact dermatitis.

Mupirocin does not have any known effects on the central nervous system that would impair a patient's ability to drive or operate heavy machinery. It does not cause drowsiness or visual disturbances when used as directed.

There are no known direct interactions between topical mupirocin and alcohol consumption. However, alcohol can sometimes impair the body's immune response to infection, so moderation is generally advised during any antibiotic treatment.

There is no 'withdrawal syndrome' associated with mupirocin. However, stopping the medication prematurely—even if the skin looks healed—can allow the remaining bacteria to multiply, leading to a relapse of the infection. It is essential to complete the full 5 to 10-day course as prescribed by your doctor.

> Important: Discuss all your medical conditions, especially kidney disease or history of skin allergies, with your healthcare provider before starting Mupirocin.

There are no documented 'absolute' contraindications for drug-drug interactions involving systemic medications, primarily because mupirocin does not enter the bloodstream in significant amounts. However, mupirocin should never be mixed with other topical creams or ointments in the same application area unless specifically directed by a physician. Mixing products can dilute the mupirocin, reducing its concentration below the level needed to kill bacteria, or it may alter the stability of the antibiotic.

• Other Topical Antibacterials: Using mupirocin simultaneously with other topical antibiotics (like neomycin or bacitracin) on the same lesion is generally discouraged. This can increase the risk of skin sensitization and makes it difficult to determine which agent is causing a side effect if an adverse reaction occurs.
• Topical Corticosteroids: While sometimes used together for infected eczema, applying a high-potency steroid and mupirocin simultaneously can sometimes mask the signs of a spreading infection. Healthcare providers usually recommend applying them at different times of the day.

• Skin Cleansers and Antiseptics: Certain harsh soaps or alcohol-based cleansers may increase the skin's permeability or cause excessive irritation when used alongside mupirocin. It is best to use a mild, non-medicated cleanser.

Since mupirocin is applied topically and has negligible systemic absorption, there are no known interactions with specific foods, including grapefruit, dairy, or high-fat meals. Diet does not affect the efficacy of this localized treatment.

There are no documented interactions between mupirocin and common herbal supplements like St. John's Wort or Ginkgo Biloba. However, patients should avoid applying herbal 'salves' or essential oils (like tea tree oil) directly over the mupirocin application site, as these can interfere with the drug's absorption and cause cumulative skin irritation.

Mupirocin is not known to interfere with standard blood or urine laboratory tests. It does not cause false positives on drug screens. However, if a wound culture is taken while the patient is actively using mupirocin, the results may show 'no growth' even if an infection is present, as the antibiotic in the sample will inhibit bacterial growth in the lab dish.

Interaction Management Strategy

1. 1Clean Slate: Always clean the skin of any previous medications before applying a new layer of mupirocin.
2. 2Sequential Application: If you must use another topical product, wait at least 30 to 60 minutes between applications to allow each product to be absorbed or set.
3. 3Communication: Ensure your doctor knows if you are using any over-the-counter medicated creams, as these are the most likely sources of interaction.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, even if they are only applied to the skin.

Mupirocin is strictly contraindicated in the following circumstances:

1. 1Hypersensitivity to Mupirocin: Any patient who has experienced a previous severe allergic reaction (anaphylaxis, angioedema, or severe rash) to mupirocin must never use the drug again. The mechanism involves an IgE-mediated immune response that can escalate in severity upon re-exposure.
2. 2Hypersensitivity to Polyethylene Glycol (PEG): This applies specifically to the ointment formulation. PEG is a common excipient in many medications and cosmetics. In sensitive individuals, it can cause contact dermatitis or systemic allergic reactions.
3. 3Ophthalmic Use: Mupirocin is not for use in the eyes. The formulations can cause severe corneal irritation or chemical conjunctivitis.

These conditions require a careful risk-benefit analysis by a healthcare professional:

• Extensive Open Wounds or Burns: Because of the risk of PEG absorption and subsequent renal toxicity, the ointment should be used with extreme caution if the skin barrier is significantly compromised over a large surface area.
• Pre-existing Renal Insufficiency: Patients with a GFR (Glomerular Filtration Rate) below 60 mL/min should be monitored closely if using the PEG-based ointment on broken skin.
• Pregnancy and Lactation: While generally considered safe, these periods require a professional assessment to ensure the benefits of treating the infection outweigh any theoretical risks to the fetus or infant.

There is no known cross-sensitivity between mupirocin and other major antibiotic classes such as penicillins, cephalosporins, or sulfonamides. This makes mupirocin an excellent alternative for patients with 'triple-antibiotic' allergies (neomycin, bacitracin, polymyxin B).

> Important: Your healthcare provider will evaluate your complete medical history, including any known allergies to 'inactive' ingredients, before prescribing Mupirocin.

FDA Pregnancy Category B: Animal reproduction studies (conducted in rats and rabbits with systemic doses many times higher than human topical doses) have failed to demonstrate a risk to the fetus. There are, however, no adequate and well-controlled studies in pregnant women. Because animal studies are not always predictive of human response, mupirocin should be used during pregnancy only if clearly needed. Most experts consider it low-risk due to the negligible systemic absorption when applied to intact skin. It is not known to affect fertility.

It is not known whether mupirocin is excreted in human milk. However, because systemic absorption is so low, it is unlikely that a nursing infant would be exposed to significant amounts of the drug. If mupirocin is applied to the breast or nipple area to treat an infection, the area should be washed thoroughly before breastfeeding to prevent the infant from direct oral ingestion of the medication.

Mupirocin is widely used and FDA-approved for pediatric patients. The ointment is approved for children as young as 2 months for impetigo. The cream is approved for children aged 3 months and older. Clinical trials have shown that the safety profile in children is similar to that in adults. Care should be taken to prevent infants from rubbing the treated area and then touching their eyes or putting their hands in their mouths.

Clinical studies of mupirocin did not include sufficient numbers of subjects aged 65 and over to determine if they respond differently from younger subjects. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function. The primary concern in the elderly is the absorption of PEG through thin or damaged skin in those with underlying kidney disease.

As previously noted, the PEG content in mupirocin ointment is the primary concern for patients with renal impairment. If the ointment must be used on patients with a GFR < 30 mL/min, it should only be applied to small, intact areas of skin. Systemic absorption of PEG can lead to an 'osmolal gap' and acute tubular necrosis in extreme cases of misuse on large wounds.

No specific studies have been conducted in patients with hepatic impairment. However, since mupirocin is rapidly converted to an inactive metabolite (monic acid) and is not dependent on complex liver enzyme pathways for its primary action or clearance, no dosage adjustments are anticipated for this population.

> Important: Special populations require individualized medical assessment. Always inform your provider if you are pregnant, planning to become pregnant, or have chronic kidney issues.

Mupirocin (pseudomonic acid A) is a unique antibacterial agent. Its molecular mechanism involves the inhibition of bacterial protein synthesis by reversibly and specifically binding to bacterial isoleucyl-transfer RNA (tRNA) synthetase. This enzyme catalyzes the formation of isoleucyl-tRNA from isoleucine and tRNA. By competing with isoleucine for the binding site on the enzyme, mupirocin prevents the loading of isoleucine onto the tRNA. This leads to a depletion of isoleucyl-tRNA, which halts the incorporation of isoleucine into peptide chains, effectively stopping bacterial protein production. Because this mechanism is distinct from other antibiotics, mupirocin shows no cross-resistance with other classes.

Mupirocin is primarily active against Gram-positive aerobic bacteria. It is highly effective against Staphylococcus aureus (including MRSA) and Streptococcus pyogenes. It also has some activity against Gram-negative bacteria like Haemophilus influenzae and Neisseria gonorrhoeae, though it is not used clinically for these. The drug's effect is concentration-dependent. At the 2% concentration found in topical products, the levels of mupirocin far exceed the Minimum Inhibitory Concentration (MIC) for susceptible bacteria, resulting in bactericidal action.

| Parameter | Value |

|---|---|

| Bioavailability | <1% (on intact skin) |

| Protein Binding | 95% to 97% (systemic) |

| Half-life | 30 - 60 minutes (as monic acid) |

| Tmax | Not applicable (topical) |

| Metabolism | Hydrolysis to Monic Acid |

| Excretion | Renal (>90% as metabolite) |

• Molecular Formula: C26H44O9
• Molecular Weight: 500.6 g/mol
• Solubility: Freely soluble in acetone and chloroform; slightly soluble in water.
• Structure: Mupirocin consists of a short fatty acid chain linked to a monic acid moiety via an ester bond. This unique structure is what prevents cross-resistance with other antibiotic classes like macrolides or lincosamides.

Mupirocin is the only member of the monoxycarbolic acid class of antibiotics. It is categorized by the FDA as an RNA Synthetase Inhibitor Antibacterial. There are currently no other drugs in this specific class available for human use, which underscores its importance in treating resistant skin infections.