Tetracyclines inhibit bacterial protein synthesis by becoming incorporated in the secretion of the sebaceous glands; they inhibit bacterial lipases and prevent the breakdown of lipids to fatty acids, which trigger inflammation (Fig. 1). According to recent guidelines, systemic antibiotic treatment combined with local treatment is the first choice in moderate and severe acne.
First generation tetracyclines such as tetracycline HCl and oxytetracycline are given in doses of 1 g daily divided into 2 doses. Second generation tetracyclines such as lymecycline 300 mg, doxycycline and minocycline 100 mg, are only given once daily. Minocycline is not registered in Norway. In more pronounced and widespread moderate acne, where low-dose tetracycline has not given a sufficient effect, higher doses of the drug should be used.
Second generation tetracyclines have a better pharmacokinetic profile and their absorption is not affected by intake of food and milk. A maximum treatment period of 3 – 4 months is recommended (5, 6), as the effect reaches a plateau after three months. Tetracycline should be combined with local treatment with retinoids and/or benzoyl peroxide, but not clindamycin solution, as this only gives a small additional benefit and increases the risk of development of resistance. There is no clinically relevant interaction between contraceptive pills and tetracyclines. Tetracycline should not be used concomitantly with systemic isotretinoin because of the risk of rise in intracranial pressure.
Erythromycin 500 mg twice daily may be tried as an alternative to tetracycline, although increased resistance to P. acnes has been described. Trimetoprim with or without sulphmetoxazole is not indicated in acne vulgaris, partly because of the risk of severe allergic reactions (6).