Oral antibiotics

Oral antibiotics are a commonly used treatment for acne, and should be considered as appropriate for moderate to severe cases. Typically, the antibiotics of choice are tetracycline or oxytetracycline. Doxycycline may be considered for people who cannot comply with oxytetracycline or tetracycline. Lymecycline is tetracycline which is taken once daily and has the advantage of not needing to be taken on an empty stomach. Erythromycin might be considered if there is no response to the other antibiotic therapies; however, it has been increasingly associated with resistant strains of propionibacteria which may explain its lack of efficacy. It has been suggested that erythromycin is reserved for patients for whom the cyclines are contraindicated, e.g. when breast feeding or when pregnant (Dreno et al., 2004). Trimethoprim is a final option but it is an off-licence use and therefore probably only to be initiated by a specialist. Minocycline has historically been the preferred antibiotic; however, safety concerns including a greater risk of a lupus erythematosustype reaction and possible permanent skin pigment changes have meant that it is rarely used. A Cochrane review considered the evidence in relation to the efficacy of minocycline in comparison with other oral antibiotics and showed no significant difference (Garner et al., 2003).

An important issue in relation to antibiotic prescribing in acne is that of resistance. It was reported that around 50% of acne sufferers in Europe were colonised with erythromycin- and clindamycin-resistant strains of P. acnes and up to 20% were colonised with cycline-resistant strains (Dreno et al., 2004). The same paper states that the longer someone is on oral antibiotics, the more likely it is for resistance to develop; they estimate that at the end of a 6 months course of antibiotics, most people would have developed resistant strains of P. acnes (Dreno et al., 2004). Antibiotic resistance should be considered as a possible cause of failure to respond to treatment, especially if they have been given over a prolonged period of time. Box 10.2 summarises the risk factors associated with developing resistant bacteria.

Box 10.2 Risk factors for bacterial resistance Long courses of antibiotics Multiple course of antibiotics Poor compliance with treatment Being close to someone who has resistant acne.     Source: Dreno et al. (2004).

The same article provides a list of recommendations for reducing the likelihood of developing resistant strains of P. acnes (see Box 10.3).

Box 10.3 Recommendations for reducing likelihood of developing resistant bacteria Do not use antibiotics where other acne treatments can be expected to bring about the same degree of clinical benefit; Use antibiotics according to clinical need (e.g. should not in general be used for mild acne); Do not use them as monotherapy; Stop the treatment when the health care professional and the patient agree that there is no further improvement or the improvement is only slight; Try to avoid using antibiotics beyond 6 months; Use BPO either concomitantly or pulsed as an anti-resistance measure; Do not swap antibiotics without adequate justification (i.e. if a further course of antibiotics is needed, use the same one) (p. 394).

Oxytetracycline and tetracycline are given in 500 mg doses twice a day whereas doxycycline is longer acting, thus given as a once-daily treatment at a dose of 100 mg. Lymecyline taken once a day in a dose of 408mg. Treatment should be given for 3 months before an assessment as to whether it is making any improvement or not. If no improvement is seen, the antibiotic should be changed; however, it should be noted that maximum improvement is usually seen at 4–6 months. More severe cases of acne may need oral antibiotics for 2 years or more (but see comments earlier with regards to resistance). Fatty food in particular decreases the absorption of tetracycline and oxytetracycline and to a lesser extent, doxycycline. Patients should be recommended where possible to take the antibiotics on an empty stomach to maximise their therapeutic value.

The most common side effects of these antibiotics are gastrointestinal disturbances which patients should be warned of.

It is generally agreed that clearing inflammatory and comedonal lesions is quicker when oral antibiotics are used in conjunction with topical retinoids and antibacterials (Gollnick et al., 2003). Thus oral treatment is not used instead of topical treatment, but as an additional therapy. The mechanisms for improved efficacy of combined therapy is in part due to the different modes of action of the various therapeutic agents (i.e. they target different aspects of the disease process). However, it is also thought that topical retinoids affect skin permeability thus enhancing topical agent penetration and increasing the cell turnover of the follicular epithelium which allows more systemic antibiotic to be transported to where the P. acnes resides (Gollnick et al., 2003).