Acne Treatment with Oral Antibiotics Doxycycline
Mechanism of action
P. acne initiates inflammatory acne. The bacteria is usually present in small numbers. P. acne proliferates in the lipid rich environment of the microcomedo and produces proinflammatory mediators that cause papules, pustules and cysts. P. acnes is highly sensitive to many antibiotics. The problem is to deliver the drug into the lipid rich environment of the microcomedo..
Topical vs. Systemic antibiotics
Moderate inflammatory acne with papules and pustules covering a wide area is treated with oral antibiotics and topical therapy. Patients treated with an oral antibiotic may be given topical antibiotics when the dose of the oral antibiotic is tapered.
The response to oral antibiotics is unpredictable. Some patients respond while other do not. It is difficult to predict who will benifit. Patients with nodular cystic acne may improve with oral antibiotic therapy, but that response is often limited. These patients frequently fail a course of oral antibiotics and topical therapy and require isotretinoin.
Patients are treated with either a prolonged course or intermittent courses of antibiotics before a complete response is achieved. Oral antibiotics are usually given for a minimum of 1 to 3 months before the dose is reduced. Once the appearance of new inflammatory lesions has decreased or stopped, the dose is gradually tapered then withdrawn. Topical retinoid therapy should be continued to maintain remission. Most P. acnes are sensitive to many antibiotics but less sensitive strains have appeared. Resistance to erythromycin has increased and limited the use of this drug.
Commonly used antibiotics
The most frequently prescribed antibiotics are tetracycline, erythromycin, doxycycline, and minocycline. Clindamycin, and trimethoprim mulfamethoxazole are very effective but are not used as first line drugs because of their potential to cause serious side effects. Tetracycline derived antibiotics are usually not given to children under the age of 7 for fear of causing tooth staining.
Doxycycline, minocycline, and trimethoprim sulfamethoxazole are more lipid-soluble and therefore more effective than tetracycline and erythromycin. P. acnes are sensitive to several antibiotics but the prevalence of P. acnes resistant to antibiotics is increasing. Typical starting dosages are tetracycline 500 mg bid, doxycycline 100 mg qd or bid, and minocycline 100 mg bid. All medications are available in generic form. P. acnes is sensitive to other antibiotics such a cephalosporins and ampicillin.
Starting dose 500 mg bid
Taper dose 250 mg bid
Not taken with dairy products
Candida albicans vaginitis
Tetracycline is inexpensive. Food, particularly dairy products, antacids, and iron interfere with the intestinal absorption. The incidence of photosensitivity is low but increase with higher doses.
Gastrointestinal intolerance is common. Candida albicans vaginitis is a common side effect. Pseudotumor cerebri in which the regulation of intracranial pressure is impaired, is a rare complication. Increased intracranial pressure causes papilledema and severe headaches.
Starting dose 20, 50, 75, 100 bid
May take with food
Candida vaginitis low incidence
Doxycycline is safe and commonly prescribed. It is less expensive than minocycline. Recent evidence indicates that very low doses such as 20 mg bid may be effective . GI intolerance is common. The incidence of photosensitivity is low but increases with increasing dose levels.
Photosensitivity reactions look like exaggerated sunburns.
Starting dose 50, 75, 100 bid
May take with food
Vertigo dose related
Rare serious reactions
Minocycline is possibly the most effective oral antibiotic. Minocycline is expensive but available as a generic. Photosensitivity does not occur. It is highly lipid-soluble and penetrates the cerebrospinal fluid, causing dose-related ataxia, vertigo, nausea, and vomiting in some patients. Pseudotumor cerebri is rarely reported. Autoimmune hepatitis, serum-sickness-like reactions and drug-induced lupus are rarely reported. A blue-gray pigmentation of the skin, oral mucosa, nails, sclera, bone and thyroid gland has been found in some patients, usually those taking high dosages for extended periods.