Hydroquinone (2%, 4.5%, 6%, 8%, 10%, 12%)

Route: Topical. Apply a thin layer to affected hyperpigmented areas once or twice daily as directed. Apply with fingertip or cotton-tipped applicator to lesional skin only; avoid normal perilesional skin where possible. Always follow application with a broad-spectrum sunscreen (SPF ≥30) during daytime hours, as sun exposure markedly reduces efficacy and can worsen hyperpigmentation. Avoid contact with eyes, mucous membranes, and broken skin.

Dosing (concentration and frequency) is entirely prescriber-determined based on indication, skin type, and tolerability:

• Standard therapeutic concentrations: 2–4% (most evidence-based, commonly used for initial therapy).
• Higher concentrations (6–12%) may be prescribed for resistant melasma or under close dermatologic supervision.
• Typical treatment duration: 3 months to 1 year continuous; cycle treatment with treatment breaks to reduce ochronosis risk.
• Higher concentrations carry greater risk of side effects and require close prescriber monitoring.

Hydroquinone is a hydroxyphenolic compound structurally analogous to melanin precursors. It inhibits tyrosinase (the copper-containing enzyme that catalyzes the conversion of tyrosine → DOPA → dopaquinone) by competing with tyrosine at the active site and chelating the catalytic copper ions. This reduces melanin biosynthesis in melanocytes. Additionally, hydroquinone inhibits the dispersion of melanosomes in dendritic projections (reducing melanin transfer to keratinocytes), disrupts cellular microtubule formation in melanocytes, and at higher concentrations may inhibit DNA/RNA synthesis preferentially in pigmented cells. Hydroquinone also acts as a free radical scavenger via electron donation.

Hydroquinone at prescriber-directed concentrations remains a cornerstone depigmenting therapy for melasma, chloasma, post-inflammatory hyperpigmentation, solar lentigines, and freckles. Compounded concentrations above 4% allow prescribers to tailor therapy for resistant or severe hyperpigmentation that does not respond to standard preparations. Higher concentrations (6–12%) are for specialist-directed use with close monitoring for adverse effects. OTC HQ products are not FDA-approved for sale in the US; prescription compounded preparations under medical supervision are the appropriate vehicle for HQ use.

Monitoring: Assess for irritant or allergic contact dermatitis at 4–8 weeks; monitor for ochronosis with chronic use (blue-black discoloration of treated areas); evaluate treatment response at 3-month intervals; counsel on rigorous daily photoprotection.

Contraindications:

• Known hypersensitivity to hydroquinone or formulation components.
• Pregnancy and lactation: systemic absorption occurs; avoid or limit use — prescriber risk-benefit assessment required.
• Application to large body surface areas: increased systemic absorption risk.

Warnings & Precautions:

• Exogenous ochronosis: paradoxical dark-blue/grey discoloration with chronic, high-concentration or extensive use; largely irreversible — limit treatment areas and duration.
• Photosensitivity: sun exposure negates efficacy and worsens pigmentation; strict photoprotection is mandatory.
• Contact dermatitis: erythema, pruritus, vesiculation at application site.
• Nail hyperpigmentation: brown discoloration with chronic use.
• At high concentrations (>4%), risk of local skin irritation and sensitization is increased.

Drug Interactions:

• Concurrent use of other photosensitizing topicals or medications may increase adverse skin reactions.
• Peroxide-containing products may cause transient facial staining on contact with HQ.

Common Side Effects: Mild burning, erythema, and dryness at application site (most common). Contact dermatitis and post-inflammatory hyperpigmentation (paradoxical) are less common. Ochronosis is rare but a significant concern with prolonged use.

Store at room temperature (15°C–25°C). Keep tightly sealed in original container; protect from light and air (hydroquinone oxidizes on exposure, turning brown — oxidized product should not be used). Do not freeze. Use within the beyond-use date assigned by Genesis Compounding.

How long does it take hydroquinone to work?

Clinical improvement in hyperpigmentation typically becomes visible within 5–8 weeks with twice-daily use, with more substantial results at 3–6 months. Higher concentrations may produce faster onset but carry greater side effect risk.

Why does the cream turn brown?

Hydroquinone oxidizes on exposure to air and light, producing a brown discoloration. An oxidized preparation should be discarded and replaced — it is less effective and may irritate the skin. Always store the preparation tightly sealed and away from direct light.

Why is hydroquinone prescription-only?

The FDA removed HQ from over-the-counter status due to concerns about long-term safety (ochronosis risk, potential cytotoxicity at high doses). Medical supervision ensures appropriate concentration, treatment duration, and monitoring for adverse effects.

What is ochronosis and how do I avoid it?

Exogenous ochronosis is a paradoxical blue-black or grey-brown discoloration of the skin that can occur with chronic, widespread HQ use — particularly at higher concentrations. It is mostly irreversible. Risk is reduced by using the lowest effective concentration, treating only the affected areas, and cycling treatment with breaks under prescriber guidance.

Is this FDA-approved?

No. This is a patient-specific, prescriber-directed 503A compounded preparation from Genesis Compounding, not FDA-approved as a compounded drug.