Erythromycin Gel 2% or 4% w/w

Cutaneous gel: Erythromycin Gel 2% or 4% w/w. Additional appearance criteria are not established by the specific text reviewed. ^[1]

Topical antibiotic for acne according to the historical source; regimen selection requires current clinical assessment. ^[1]

Erythromycin 90–115% of prescribed amount. HPC: 300–560 mPa·s at 2% m/v in water, 20 °C. ^[1]

Protect erythromycin raw material from light. ^[2]

No oxidative stability study of the finished mixture or inert-atmosphere requirement is provided. Use the source container. ^[1]

No quantitative hydrolytic stability limit is given for this formula. Retain the prescribed water amount and quality. ^[1]

Erythromycin is hygroscopic. ^[2]

For the finished product the source specifies:
Tube; 15–25 °C.
Erythromycin raw material: the source specifies ≤30°C. This does not establish a BUD. ^{[1], [2]}

Erythromycin is unstable in acidic media. ^[2]

No complete compatibility test with added actives or alternative excipients is provided. Substitutions require separate evidence. ^[1]

Hydroxypropylcellulose: white to yellowish powder forming a viscous liquid with water. Use the grade/viscosity specified by the formula. ^[4]

Clean long-sleeved laboratory clothing, hair covering and gloves during handling; change gloves after contamination or damage.
Contain powder during weighing and trituration and use eye protection; select respiratory protection for the actual exposure. ^{[1], [3], [5]}

Reference batch: 50 g — επιλογή μίας στήλης / choose one strength. First ingredient: Erythromycin, 1.10 g (2%) / 2.20 g (4%) βλ. ποσότητα / see quantity. Independently check chemical form, units and every scale conversion before weighing.
Check homogeneity, aggregates, separation and actual yield before subdivision. Packaging should allow uniform application without introducing water into the contents.
For the local assessment record quantity per preparation, work frequency, duration of open handling, potential exposure routes and effectiveness of controls. These are assessment inputs; no fictitious final risk score is assigned.
Volatile solvent in this formula: Denatured ethanol 96% v/v, FTM grade 22.5 g. Exclude ignition sources and minimise vapours/open evaporation. Check ventilation, electrical equipment and container compatibility with the specific solvent.
Release checkpoint: inspect aggregates, crystals, local texture differences and free liquid after completing the method. Record mixing geometry, batch size and actual temperatures; copying rpm to another mixer does not establish process equivalence. ^{[1], [2], [3], [5], [8], [10]}

Before mixing: verify each ingredient’s chemical form and lot, record theoretical amounts and check equipment cleanliness. Follow the temperatures and addition sequence in the procedure below. ^{[1], [5]}

Period reported by source: Historical validity: 2 months; in-use limit 2 months, within overall expiry.
This duration is a specific formulary/source instruction. This review did not verify a complete primary study establishing chemical, physical and microbiological extension for the same finished formulation.
Selected general rule: up to 35 days for an aqueous form appropriately preserved in its final composition and pH. Use 20–25 °C, or 2–8 °C only where permitted/required by the source and compatible with the dosage form. A preservative name is insufficient if it is diluted, inactivated or partitioned into another phase.
The reference-policy ceiling in this edition is the shorter of the source period above and the general ceiling. Extension needs matching active/excipients/strength, container, temperature, a stability-indicating method and the required microbiological evidence for aqueous extension. An applicable official USP–NF compounded monograph is assessed separately in its complete text.
Use-by date = the earliest allowed date from preparation plus selected period, ingredient expiries and any shorter supported limit. In-use dating never extends overall BUD. Complete the actual date for the batch after the required checks.
A default is a conservative dating limit, not experimental proof of batch stability. Its category depends on final composition, preservation and permitted temperatures. Water percentage or loss on drying does not determine aw. Document using SOP-014/F-006; use SOP-017/F-012 for specific aw evidence.
USP clarification: aw measurement is not required for every nonsterile preparation. Category assignment may use the exact composition and relevant representative examples; an uncertain or borderline formulation is best assessed by a suitable specific measurement. This edition contains no measured aw or released batch. The final preparation generally must not outlast the remaining BUD of its compounded bases/intermediates. An exception requires specific justification that physical, chemical and microbiological quality is not adversely affected. Record the final limit, intermediate preparation dates and their actual expiry dates separately. ^{[1], [6], [7], [9], [11]}

No separately registered base is required. Any commercial vehicle remains the exact named product in the formula table. ^[1]

Balance with suitable minimum weight, mortar/pestle or homogeniser, mixing vessels, spatulas, thermometer for heated processes and volumetric equipment for mL quantities. ^[1]

Boil 25 g water, cool to ~75 °C and disperse cellulose. Stir to room temperature; refrigerate 1 hour. Dissolve acid and erythromycin in ethanol. Incorporate into gel, cover, refrigerate 1 hour and adjust mass with freshly boiled and cooled water. ^[1]

Source includes a 10% manufacturing overage for degradation, not a new labelled strength. Record selection of 2% or 4%. ^[1]

Tube as specified by the procedure. ^[1]

Erythromycin 90–115% of prescribed amount. HPC: 300–560 mPa·s at 2% m/v in water, 20 °C.
Record the method, acceptance criterion, actual result and reviewer separately in F-005. A critical specification failure requires quarantine and investigation under SOP-015; retesting needs justification. ^{[1], [10]}

Tube; 15–25 °C. ^[1]

Dispense with a clear route, strength and use-by date. Complete amount per application and frequency from the prescription. ^[1]

Erythromycin Gel 2% or 4% w/w
External use
Quantity: ____ Batch: ____
Prepared: ____ Use by: ____
Patient / dose / frequency: ____
Storage: Tube; 15–25 °C.
Temperature for this batch BUD: ____ ^[1]

The numeric value is a literature reference ceiling subject to its specific conditions. No actual batch BUD has been assigned and no aw measurements have been produced. The exact formula, prerequisites, container, storage and quality evidence require approval for the actual application. The BUD clock starts when compounding begins. Use the shortest applicable supported limit and assess in-use dating separately. USP categories are a technical framework and are not presented as Greek legislation.