NB-UVB Dosing Protocol for Vitiligo
NB-UVB phototherapy should be administered three times weekly, with initial dosing based on skin type ranging from 130-400 mJ/cm² and subsequent dose increases of 10% per treatment, with an arbitrary safety limit of 200 total treatments for skin types I-III. 1
Initial Dosing Strategy
Skin type-based dosing is the standard approach, with the following starting doses 1:
- Skin Type I: 130 mJ/cm², increase by 15 mJ/cm² per treatment
- Skin Type II: 220 mJ/cm², increase by 25 mJ/cm² per treatment
- Skin Type III: 260 mJ/cm², increase by 40 mJ/cm² per treatment
- Skin Type IV: 330 mJ/cm², increase by 45 mJ/cm² per treatment
- Skin Type V: 350 mJ/cm², increase by 60 mJ/cm² per treatment
- Skin Type VI: 400 mJ/cm², increase by 65 mJ/cm² per treatment
For Asian patients specifically, evidence suggests these conventional starting doses may be suboptimal, as minimal erythema dose (MED) testing in Asian vitiligo patients showed a range of 300-700 mJ/cm² for lesional skin, indicating higher starting doses may be appropriate. 2
Alternative MED-Based Protocol
If MED testing is performed (generally recommended for NB-UVB due to the broad range of MED by skin type), start at 50% of the measured MED and increase by 10% of the initial MED for treatments 1-20. 1
Treatment Frequency and Duration
Administer treatments three times weekly (this is the standard convention). 1 Some studies have used twice-weekly protocols with success, though three times weekly is preferred. 3, 4
Continue treatment until maximum repigmentation is achieved, typically requiring 15-20 treatments to see initial response. 1 However, patients who respond within the first month of treatment are significantly more likely to achieve satisfactory repigmentation (>75%), making early response a key prognostic indicator. 4
Dose Adjustments for Missed Treatments
Apply the following dose reduction protocol 1:
- 4-7 days missed: Keep dose the same
- 1-2 weeks missed: Decrease dose by 25%
- 2-3 weeks missed: Decrease dose by 50% or restart protocol
- 3-4 weeks missed: Restart protocol from beginning
Maximum Treatment Limits
The arbitrary safety limit is 200 treatments for skin types I-III, which is more stringent than limits applied to psoriasis due to the greater susceptibility of vitiliginous (melanin-deficient) skin to sunburn and photodamage. 1 For skin types IV-VI, this limit could be higher at the clinician's discretion with patient consent. 1
This 200-treatment limit contrasts with the 150-treatment maximum for PUVA in vitiligo, reflecting PUVA's higher photodamage risk. 5
Site-Specific Response Expectations
Hands and feet respond poorly to NB-UVB regardless of treatment duration or total dose, with studies showing less than 25% repigmentation in all cases. 3 Facial lesions respond best, with 34.4% of patients achieving cosmetically acceptable (>75%) repigmentation on the face versus only 7.4% on the body. 4
Patients must be counseled before starting treatment that hands and feet respond poorly in all patients, and that not all body sites respond equally. 1, 5
Predictors of Treatment Success
Darker skin phototypes (III-V) have significantly greater likelihood of achieving >75% repigmentation on facial lesions. 4 Patients without prior PUVA exposure respond significantly better (67% response rate) compared to those previously treated with PUVA (36% response rate, P=0.003). 3
Special Populations
For children, NB-UVB has been shown safe and effective, though initial doses should be reduced by approximately 25% from adult dosing. 1 Pregnancy is not a contraindication to NB-UVB therapy. 1
For patients with history of radiotherapy, use lower initial doses, avoid previously irradiated areas (especially those with radiation dermatitis or fibrosis), and monitor for radiation recall dermatitis. 6, 5
Critical Safety Monitoring
Meter the UVB machine weekly, as lamps steadily lose power and failure to calibrate actual output can result in delivering much lower doses than intended. 1
Use protective goggles in all patients and genital shields in male patients during every treatment. 1
Common Pitfall to Avoid
Do not continue treatment beyond 40-50 exposures if the patient shows less than 25% improvement, as this indicates non-response and further treatment is unlikely to be beneficial. 3 The British Association of Dermatologists emphasizes that NB-UVB does not alter the natural history of vitiligo, and 12% of patients may end up with worse vitiligo than before treatment started, even after initial response. 1