If you've tried over-the-counter (nonprescription) acne products for several weeks and they haven't helped, your doctor can prescribe stronger medications. A dermatologist can help you:

• Control your acne
• Avoid scarring or other damage to your skin
• Make scars less noticeable

Acne medications work by reducing oil production, speeding up skin cell turnover, fighting bacterial infection or reducing inflammation — which helps prevent scarring. With most prescription acne drugs, you may not see results for four to eight weeks, and your skin may get worse before it gets better. It can take many months or years for your acne to clear up completely.

The treatment regimen your doctor recommends depends on your age, the type and severity of your acne, and what you are willing to commit to. For example, you may need to wash and apply medications to the affected skin twice a day for several weeks. Often topical medications and drugs you take by mouth (oral medication) are used in combination. Pregnant women will not be able to use oral prescription medications for acne.

Talk with your doctor about the risks and benefits of medications and other treatments you are considering.

Topical medications

The most common topical prescription medications for acne are as follows:

• Retinoids and retinoid-like drugs. These come as creams, gels and lotions. Retinoid drugs are derived from vitamin A and include tretinoin (Avita, Retin-A, others), adapalene (Differin) and tazarotene (Tazorac, Avage). You apply this medication in the evening, beginning with three times a week, then daily as your skin becomes used to it. It works by preventing plugging of the hair follicles.
• Antibiotics. These work by killing excess skin bacteria and reducing redness. For the first few months of treatment, you may use both a retinoid and an antibiotic, with the antibiotic applied in the morning and the retinoid in the evening. The antibiotics are often combined with benzoyl peroxide to reduce the likelihood of developing antibiotic resistance. Examples include clindamycin with benzoyl peroxide (Benzaclin, Duac, Acanya) and erythromycin with benzoyl peroxide (Benzamycin). Topical antibiotics alone aren't recommended.

• Salicylic acid and azelaic acid. Azelaic acid is a naturally occurring acid found in whole-grain cereals and animal products. It has antibacterial properties. A 20 percent azelaic acid cream seems to be as effective as many conventional acne treatments when used twice a day for at least four weeks. It's even more effective when used in combination with erythromycin. Prescription azelaic acid (Azelex, Finacea) is an option during pregnancy and while breast-feeding. Side effects include skin discoloration and minor skin irritation.

  Salicylic acid may help prevent plugged hair follicles and is available as both wash-off and leave-on products. Studies showing its effectiveness are limited.

• Dapsone. Dapsone (Aczone) 5 percent gel twice daily is recommended for inflammatory acne, especially in adult females with acne. Side effects include redness and dryness.

Evidence is not strong in support of using zinc, sulfur, nicotinamide, resorcinol, sulfacetamide sodium or aluminum chloride in topical treatments for acne.