EVIDENCE-BASED ANSWER
Adverse reactions to long-term tetracycline therapy are rare, and most will occur within 2 months of initiating therapy (strength of recommendation [SOR]: B, systematic review of ecological studies). Rare but serious drug reactions include a severe cutaneous reaction, hypersensitivity syndrome reaction, serum sickness–like reaction, and isolated single-organ dysfunction (SOR: B, systematic review).
Duration of antibiotic treatment is strongly associated with increased bacterial resistance (SOR: B, systematic review and 1 outcomes study), but antibiotics for acne do not appear to interfere with oral contraceptive efficacy (SOR: B, case-control study and supporting expert opinion). Laboratory monitoring is not indicated in otherwise healthy patients (SOR: B, consistent cohort studies).
No reports have been published regarding long-term topical tretinoin (Retin A) therapy. Short-term follow-up reports note no systemic effects (SOR: C, expert opinion), no teratogenicity (SOR: B, single case control study), and negligible systemic absorption (SOR: B, outcome studies). Thus, long-term topical tretinoin is presumed to be safe (SOR: C, expert opinion and extrapolation of pharmacologic data).
Evidence summary
Tetracycline
A study of the safety of tetracycline,1 which used reports in a drug safety database and a literature review of reported adverse events, concluded that rare but serious events do occur with tetracycline. Severe cutaneous adverse reaction was the most common reported single-organ dysfunction. Other rare events included hypersensitivity syndrome reactions and serum sickness–like reactions.
Since baseline rates of tetracycline use are unknown, it is impossible to ascertain the event rates for these rare reactions. Most of these serious adverse events occur less than 2 months after initiating therapy; they typically include general symptoms such as fever, malaise, and arthralgias, but may also include major organ involvement. The study suggested no clear treatment for these complications, but recommended discontinuing tetracycline and avoiding the entire tetracycline class of drugs.1 No evidence supports previous concerns that tetracycline causes drug-induced lupus.
A systematic review confirms that treating acne with long-term systemic antibiotics leads to increased antimicrobial resistance.2,3 A well-designed cohort trial showed that Propioni-bacteri-um acnes resistance was directly related to duration of antibiotic therapy.4 This is clinically important because resistance levels correlate with therapeutic failure.2 Rotating antibiotics on a long-term basis actually increases bacterial resistance patterns and can exacerbate the problems of increasing resistance and poor treatment outcomes.2
A relatively large retrospective cohort study of oral contraceptive users in a dermatological practice showed no difference in contraceptive failure rates between those prescribed common antibiotics (including tetracycline) and controls (1.6% vs 0.96%; 95% confidence interval [CI] for the difference, 0.81–2.1).5
A systematic review of 8 studies reported on 777 patients taking antibiotics for acne, and examined the need for laboratory monitoring of long-term tetracycline users, including renal, liver, and blood components. The authors found only 1 adverse drug reaction (mild hyperbilirubinemia). They concluded that routine lab monitoring for all patients on long-term antibiotics for acne rarely detects clinically concerning adverse drug reactions and would be cost-prohibitive.6
Minor adverse side effects of tetracycline therapy are reported in about 8% of patients.7 Some of the relatively more common and benign side effects are summarized in Table 1.
TABLE 1
Side effects of tetracycline and topical tretinoin
| Tetracycline | Side-effect rates |
|---|---|
| Vaginal candidiasis8 | 12% |
| Gastrointestinal complaints8 * | 4% |
| Gram-negative folliculitis9 | 4% |
| Topical tretinoin10 | Maximal observed side-effect rates |
| Peeling | 50% |
| Burning | 49% |
| Erythema | 49% |
| Skin tightness | 42% |
| Dryness | 40% |
| Itching | 24% |
| * Gastrointestinal complaints included nausea, diarrhea, black hairy tongue, esophagitis, and flatulence. | |