This study is designed to evaluate the pharmacokinetics of solamargine of SR-T100 gel. As safety parameters, adverse events, and vital signs (blood pressure, heart rate, and body temperature) will be recorded.

In the study period, a single dose of 2 g topical SR-T100 gel (containing 2.3% solamargine in Solanum undatum plant extract) in 100 cm2 skin area covered by an occlusive dressing will be administered. Sampling Time Schedule: 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 16, 20, 24, 36 hours after dosing.

Inclusion Criteria:

1. Male or female is 20 years of age or above.
2. Patient has AK lesions located within a 100 cm2 contiguous or non-contiguous treatment area.
3. Patient has at least one clinical confirmed AK lesion within the selected treatment area before.

Exclusion Criteria:

1. Patient had used the following treatments within 4 weeks prior to the study treatment initiation: immunomodulators or immunosuppressive therapy, interferon, cytotoxic drugs.
2. Patient had treated with topical 5-FU, diclofenac gel, imiquimod, ingenol mebutate, corticosteroids, retinoids, masoprocol on the treatment area within 4 weeks prior to the study treatment initiation.
3. Patient had received cryodestruction, chemodestruction, curettage, photodynamic therapy, surgical excision on the treatment area within 4 weeks prior to the study treatment initiation.
4. Patient had received any of the following treatments on the treatment area in the 6 months before study treatment initiation: psoralen plus UVA therapy, UVB therapy, laser abrasion, dermabrasion, chemical peel.
5. Patient had used any topical preparations, such as sunscreens, moisturizers, body oils, or alpha or beta hydroxyl acids, in the treatment area within 24 hours before and during the study course.
6. Use of any medication, including over the counter products, herb medicine and dietary supplements such as vitamins, which would interfere with study results, within one week before and during the study course.
7. Patient is known to be hypersensitive to the study medication.
8. Female who is pregnant, breast-feeding or considering becoming pregnant while on the study.
9. Donation of 500 ml of blood in the past 3 months prior to dosing or donation of 250 ml of blood in the past 2 months prior to dosing.
10. Patient had used of any investigational drug within the past 30 days before enrollment.
11. Patient has any dermatological disease and/or condition, such as atopic dermatitis, basal cell carcinoma, eczema, psoriasis, rosacea, squamous cell carcinoma, melanoma, or other possible confounding skin conditions in the treatment or surrounding area (5 cm distances from treatment area).