What is the recommended dosage of doxycycline (antibiotic) for acne treatment?

Doxycycline Dosage for Acne

For adults and children over 100 pounds, start with 200 mg on the first day (100 mg every 12 hours), followed by a maintenance dose of 100 mg daily. 1, 2

Standard Dosing Regimen

Adults and Children >100 pounds

• Loading dose: 200 mg on day 1, administered as 100 mg every 12 hours 1, 2
• Maintenance dose: 100 mg daily thereafter 1, 2
• Take with adequate fluids in upright position to reduce esophageal irritation 2
• May be taken with food or milk if gastric irritation occurs 2

Children 8 years and older weighing <100 pounds

• Loading dose: 2 mg/lb body weight divided into 2 doses on day 1 1, 2
• Maintenance dose: 1 mg/lb body weight daily (as single dose or divided into 2 doses) 1, 2
• For more severe infections, up to 2 mg/lb may be used 2

Alternative Low-Dose Regimen

Subantimicrobial-dose doxycycline (20 mg twice daily or 40 mg extended-release daily) has demonstrated efficacy in moderate inflammatory acne. 1, 3, 4

• This dosing reduces gastrointestinal side effects and photosensitivity risk 5, 4
• Does not detectably affect antibiotic resistance of skin flora 5
• Results in 84% reduction in papules and 90% reduction in pustules at 3 months 4

Critical Treatment Principles

Never Use as Monotherapy

Doxycycline must always be combined with topical benzoyl peroxide and/or a retinoid to prevent bacterial resistance. 1, 3

• Concomitant topical therapy should continue throughout treatment and for maintenance after antibiotic discontinuation 1
• Monotherapy with systemic antibiotics is explicitly contraindicated 1

Duration of Treatment

• Limit systemic antibiotic use to the shortest possible duration 1, 3
• Re-evaluate at 3-4 months to assess response and minimize bacterial resistance development 1, 3
• Treatment should not routinely extend beyond 3-4 months 3, 6

Indications for Use

Doxycycline is indicated for moderate to severe inflammatory acne, not for mild cases. 1, 3

• Use only when acne is resistant to topical treatments 1, 3
• For mild acne, topical therapies (retinoids, benzoyl peroxide) are first-line 3
• Consider doxycycline only if acne progresses to moderate-severe or topical therapies have failed 3

Common Adverse Effects and Management

Gastrointestinal Effects

• Nausea, vomiting, diarrhea occur more frequently than with minocycline 1, 3, 6
• Incidence approximately 15.7% vs 5.9% with placebo 1
• Taking with food and adequate fluids in upright position reduces GI side effects 1, 2
• Risk of esophagitis and esophageal ulceration if not taken properly 1, 2

Photosensitivity

• Dose-dependent phototoxic reactions are common 3, 6, 7
• At 100 mg daily, incidence is approximately 3% 7
• At doses ≥150 mg daily, incidence increases significantly 7
• Strict sun protection is mandatory during treatment 3

Treatment Discontinuation

• Adverse effects requiring cessation occur in approximately 1.3% of patients 1

Absolute Contraindications

Do not use doxycycline in:

• Children <8 years of age (risk of permanent tooth discoloration and bone growth inhibition) 1, 3
• Pregnant women (Pregnancy Category D) 1, 3
• Nursing mothers (distributed into breast milk) 1, 3
• Patients with hypersensitivity to tetracyclines 1

Important Drug Interactions

Doxycycline interacts with multiple medications that reduce absorption or efficacy: 1

• Antacids containing aluminum, calcium, or magnesium
• Iron-containing preparations
• Bismuth subsalicylate
• Proton-pump inhibitors
• Hormonal contraceptives (may reduce contraceptive efficacy)
• Oral anticoagulants (monitor INR)
• Isotretinoin (avoid concurrent use)

Clinical Pearls

• Standard-dose doxycycline (100 mg daily) and minocycline show similar efficacy, with no clear superiority of either 1, 6
• Both are more effective than tetracycline 1
• Doxycycline has longer half-life than tetracycline, allowing once-daily dosing 6
• Therapeutic antibacterial serum activity persists for 24 hours following recommended dosage 2
• Absorption is not markedly influenced by simultaneous food or milk ingestion 2
• Does not accumulate excessively in patients with renal impairment at usual doses 2