1. Drugs used in dermatological conditions

2. The skin the skin is the largest organ, 4 kg & 2m2
important functions as, defense, physical barrier, heat regulation, sensation, vitamin D synthesis
Composed of 3 layers, epidermis, dermis & subcutaneous fatty tissue
Both topical & systemic medications can be used depending on nature & extent of disease

4. Topical preparations Convenient & minimize systemic side effects
Formulated as cream, ointment, lotion, spray, gel, paste, powder, & packed dressings
Bioavailability depends on the vehicle (oil or water) & method used to localize it.
Efficacy depends on: thickness of skin, concentration, frequency of application, age & health of skin
Generally lipophilic more readily absorbed than hydrophilic

5. Drugs used in acne Pathogenesis of acne
Retinoids: vitamin A derivatives, used in acne, psoriasis & photoaging
The first generation: topical Tretinoin (Retin A), & systemic Isotretinoin (Roaccutane) only in severe cystic acne
The 3rd generation as adapalene & tazarotene, more effective & less irritating, in comedonal & inflammatory acne.

8. mechanism of action
Acts on proliferation & differentiation of keratinocytes
Immune function
Anti inflammatory action
In first generation reduction of sebum production
Their action is on the nucleus by binding to a specific receptor & acts as a transcription factor thereby influencing cell differentiation & proliferation
Side effects of topical: dryness, irritation, peeling
Systemic: Teratogenic, depression & suicide, dryness of skin & mucosa

9. Other agents for acne
Benzoyl peroxide: antiseptic & comedolytic, in mild to moderate non inflammatory acne, also irritant, many over the counter preparations
Azelaic acid: antibacterial, anti-inflammatory, anticomedogenic, mild to moderate inflammatory acne, irritant
Antibiotics: inhibit the growth of p.acnes in moderate to severe inflammatory acne, topical mainly clindamycin & erythromycin solution, also available are dapsone(sulfon) solution & metronidazole gel.
systemic antibiotics mainly minocycline, doxycycline & erythromycin.

10. Antibacterial agents
Many gram positive & gram negative organisms infect the skin
In gram positive infections as staphylococcal & streptococcal infections we can use topical antibacterial agents such as fucidin, mupirocin & bacitracin
In gram negative infections as by E-coli, pseudomonas , & klebsiella we can use polymixin which is sometimes mixed with neomycin & bacitracin forming the “triple antibiotic”

11. Agents used for ectoparasites
Mainly pediculosis & scabies, the most commonly used:
1- lindane: pediculicide & scabicide
2- permethrin in conc. 1% in pediculosis & 5% in scabies
3- synergized pyrithrins: pesticide with a substance to augment its effect, first line in pediculosis
4- crotamiton: scabicide & antipruritic with unknown mechanism of action
5- sulfur preparation in 5% & 10% concentrations are the best in scabies
6- oral ivermectin

13. Agents used for pigmentation
Hyperpigmentation as chloasma & freckles, use temporary whitening preparations as hydroquinone in 2% & 4% concentration
Inhibit tyrosinase enzyme involved in melanin synthesis
Avoid higher concentration & longer duration due to risk of carcinogenicity
Hypopigmentation as in vitiligo: methoxsalen is a photoactive substance (psoralen), stimulate melanocytes but needs UV radiation, forms the PUVA
Inhibit DNA synthesis & cell differentiation
Topical for small patches & systemic for large

15. corticosteroids
They have anti-inflammatory & immunosuppressive effects
Used for treating many itchy & inflammatory diseases like eczema & psoriasis
They inhibit the arachidonic acid cascade, inhibit the production of cytokines & act on inflammatory cells
Repeated use can lead to tachyphylaxis
Different potencies as weak, medium strength, high strength & very high strength.

16. corticosteroids Side effects
Skin atrophy, stria, purpura, acneiform rash, dermatitis, local infection & hypopigmentation
In children potent steroids applied to a wide area can cause systemic effects as inhibiting the hypothalamic-pituitary-adrenal axis with ardrenal insufficiency & growth retardation

17. Trichogenic agents
1- minoxidil: originally oral antihypertensive, but noticed to increase hair growth as a side effect
Very effective in androgenic alopecia (male & female pattern baldness)
Available as a topical solution & shampoo
Might shorten the rest phase in hair cycle
Should be used continuously to exert its effect

18. Trichogenic agents
2- finasteride: an oral 5α reductase inhibitor preventing the conversion of testosterone to the active form 5α dihydrotestosteron (DHT) which play a key role in androgenic alopecia
Side effects include decreased libido, ejaculation & erectile dysfunction
Contraindicated in pregnancy as it may cause hypospadias in a male fetus