Antibiotics (orally administered)
The duration of most oral therapy regimens is at least 3 - 6 months.
The administration of oral antibiotics is indicated for moderate to severe acne, in patients with inflammatory disease, in whom combinations of topical agents have failed or are not tolerated, for the treatment of chest, back, or shoulder acne, or in patients in whom absolute control is deemed essential, such as those who scar with each lesion or develop inflammatory hyperpigmentation. It generally takes 6 – 8 weeks to judge efficacy. Starting at a high dose and reducing it after control is preferred. Working to maintain control eventually with topical retinoids or retinoid – benzoyl peroxide combination therapy is ideal. Nevertheless, keeping patients free of disease for 1 – 2 months before each decrease in dosage is best to prevent flaring. The duration of most oral therapy regimens is at least 3 – 6 months.
There is concern that oral antibiotics may reduce the effectiveness of oral birth control pills. Since this association has not been confirmed yet (apart from rifampin, which is not used for acne) it is best to discuss with patients whether it is appropriate to use an additional birth control method.
Tetracycline is the most safe and cheap choice, while giving a positive response in many patients. It is usually administered initially at a dose of 250 – 500 mg between 1 and 4 times a day, which is gradually reduced, depending on clinical response. It is best taken on an empty stomach, at least 30 minutes before a meal and 2 hours afterwards. This is something that often limits dosage to twice a day. Calcium or iron in food supplements is combined with tetracycline, reducing absorption by as much as half.
Tetracycline therapy may lead to the development of vaginitis or perianal itching in about 5% of patients, with Candida albicans usually present in the involved site. Gastrointestinal symptoms, like nausea, are the only other common adverse effect of tetracycline. To reduce the incidence of esophagitis, tetracyclines should not be taken at bedtime. Staining of growing teeth occurs, which precludes its use in pregnant women and in children under the age of 9 or 10 years old. Tetracycline should also be avoided in persons with impaired renal function.
Doxycycline is usually administered once or twice a day at a dose of 50 – 100 mg, depending on disease severity. Photosensitivity reactions are not uncommon when doxycycline is administered, and these reactions can be dramatic. Subantimicrobial-dose doxycycline, doxycycline hyclate 20 mg, may be given twice daily. The advantage of this is that the anti-inflammatory activity is being utilised but no antibiotic resistance results because of the low dose. A formulation providing sustained-release (40 mg) is also available. However, these low-dose preparations appear to have low efficacy.
This is the most effective oral antibiotic for the treatment of acne vulgaris. In cases where P. acnes develops resistance to tetracycline, minocycline is an alternative. The usual dose is 50 – 100 mg once or twice a day, depending on disease severity. Its absorption is less affected by milk and food as compared to the absorption of tetracycline. Since it is possible that vertigo may occur, it is best to initiate therapy with a single dose in the evening. An extended-release preparation is also available, limiting the vestibular side effects. Other effects that may be noticed include pigmentation in areas of inflammation, of oral tissues, in postacne osteoma or scars, in a photodistributed pattern, on the shins, in the sclera, nailbed, ear cartilage, teeth, or in a generalised pattern. Moreover, other uncommon, yet serious side effects include the following: lupus-like syndromes, a hypersensitivity syndrome (consisting of fever, hepatitis, and eosinophilia), serum sickness, pneumonitis, and hepatitis.
People who cannot take tetracyclines due to their side effects or women who are pregnant but should take oral antibiotic therapy, have the option of erythromycin. Its efficacy is low, and among its adverse effects, gastrointestinal upset is the most common. Vaginal itching occurs rarely. The initial dose is 250 – 500 mg and it is administered 2 – 4 times a day, while gradual reduction starts once control of acne has been achieved. It is possible that erythromycin will increase the levels of other drugs that are metabolised by the cytochrome P450 system in the blood.
In previous years, clindamycin seemed to give an excellent response in acne treatment. However, its use has been limited significantly due to the potential for the development of pseudomembranous colitis, and the availability of retinoids. The initial dose is 150 mg three times a day, reduced gradually while acne control is achieved.
In certain cases, sulfonamides may be prescribed, but their use is quite limited due to their potential to cause severe drug eruptions. Trimethoprim–sulfamethoxazole (Bactrim, Septra), in double-strength doses twice a day initially, is effective in many cases unresponsive to other antibiotics. Another useful antibiotic is trimethoprim administered as monotherapy at a dose of 300 mg twice a day. Another alternative treatment is amoxicillin, in doses from 250 mg twice daily to 500 mg three times a day; amoxicillin can be also used during pregnancy as it falls into pregnancy category B. Although rarely used today, dapsone has been administered in severe acne conglobata. Nevertheless, usually isotretinoin is preferred.
The antimicrobial resistance of P. acnes constitutes a clinically relevant problem. Resistance to erythromycin and clindamycin is quite widespread, usually occurring simultaneously. When P. acnes becomes resistant to tetracycline, it is also resistant to doxycycline, so if lack of efficacy due to prolonged oral therapy with one of them is suspected, it would be necessary to switch to minocycline. Although cutaneous drug resistance problems may be limited through the concomitant use of benzoyl peroxide, it is now appreciated that Staphylococcus aureus in the nares, streptococci in the oral cavity, and enterobacteria in the gut may also become resistant, and close contacts, including treating dermatologists, may harbour such drug-resistant bacteria. Antibiotic resistance prevention strategies include limiting the duration of treatment, stressing the importance of adherence to the treatment regimen, restricting the use of antibiotics to inflammatory acne, encouraging retreatment with the same antibiotic unless its efficacy has been lost, avoiding the use of different oral and topical antibiotic agents simultaneously, and using isotretinoin if unable to maintain clearance without orally administered antibacterial treatment.
You might also like to read: