Prescription errors. Legibility and drug name confusion.

Inadvertent drug substitution occurred in several instances in our practices due to the combination of the physician's illegible handwriting on prescriptions and the pharmacist's misinterpretation of subtle clues, which might have prevented the errors. The literature on the legibility of physician handwriting is reviewed. Our specific recommendations include using preprinted prescription pads, training staff assistants who write prescriptions, printing complete directions on each prescription, and aggressively educating each patient about the name and purpose of all drugs being prescribed. Patients are encouraged to bring their medications to each office visit to identify potential errors.

Oral contraceptive failure rates and oral antibiotics.

BACKGROUND: Despite anecdotal evidence of a possibility of decreased effectiveness of oral contraceptives (OCs) with some antibiotics, it is not known whether antibiotic use in dermatologic practices engenders any increased risk of accidental pregnancy. OBJECTIVE: Our purpose was to examine the effect of commonly prescribed oral antibiotics (tetracyclines, penicillins, cephalosporins) on the failure rate of OCs. METHODS: The records from three dermatology practices were reviewed, and 356 patients with a history of combined oral antibiotic/OC use were surveyed retrospectively. Of these patients, 263 also provided "control" data (during the times they used OCs alone). An additional 162 patients provided control data only. RESULTS: Five pregnancies occurred in 311 woman-years of combined antibiotic/OC exposure (1.6% per year failure rate) compared with 12 pregnancies in 1245 woman-years of exposure (0.96% per year) for the 425 control patients. This difference was not significant (p = 0.4), and the 95% confidence interval on the difference (-0.81, 2.1) ruled out a substantial difference (> 2.1% per year). There was also no significant difference between OC failure rates for the women who provided data under both conditions, nor between the two control groups. All our data groups had failure rates below the 3% or higher per year, which are typically found in the United States. CONCLUSION: The difference in failure rates of OCs when taken concurrently with antibiotics commonly used in dermatology versus OC use alone suggests that these antibiotics do not increase the risk of pregnancy. Physicians and patients need to recognize that the expected OC failure rate, regardless of antibiotic use, is at least 1% per year and it is not yet possible to predict in whom OCs may fail.

PIP: Although some antibiotics are assumed to compromise the effectiveness of oral contraceptives (OCs), it is unknown whether the antibiotics used in dermatologic practice are associated with such a risk. To address this issue, a review was conducted in three US dermatologic practices of the records of 356 patients with a history of combined oral antibiotic/OC use in 1990-95 who responded to a follow-up questionnaire. 263 of these patients provided control data during the times they used OCs alone and an additional 162 patients were controls only. There were five pregnancies in 311 woman-years of combined antibiotic/OC exposure (1.6% annual failure rate) compared with 12 pregnancies in 1245 woman-years of exposure among controls (0.96% annual failure rate)--a nonsignificant difference. In addition, there were no significant differences between OC failure rates among women who served as both cases and controls or between the two control groups. All five cases who became pregnant had been taking an antibiotic (microcycline or a cephalosporin) for at least 3 months. Side effects potentially linked to reduced OC effectiveness (e.g., diarrhea, breakthrough menstrual bleeding) were not reported by the women who became pregnant. It is presumed that inter-individual differences in steroid plasma levels are a more important cause of OC failure than concomitant antibiotic therapy.

A practical approach to antibiotic treatment in women taking oral contraceptives.

Clinical situations that require the use of systemic antibiotic therapy are common. Because millions of women choose oral contraceptives for birth control, the potential for interaction between these drugs frequently has to be considered. We review the available information and present a practical approach for dealing with this situation based on sharing responsibility with an educated patient.

PIP: A 38-year-old woman with impetiginized eczema, who was treated with oral cefadroxil, 500 mg twice daily for 10 days, subsequently became pregnant and threatened the physicians who prescribed the antibiotic with a "wrongful birth" lawsuit because she was told that the antibiotic may have interfered with her low-estrogen oral contraceptives (OCs). Although it was proved that the women became pregnant 6-8 weeks after taking the cefadroxil, the physicians involved were inspired by this experience to research the literature on the interaction of antibiotics and oral contraceptives and to devise a practical approach for such situations. As a result of their data collection, they devised 3 categories of antibiotics ranging from those which likely reduce the effectiveness of OCs (rifampicin) to those which are associated with OC failure in 3 or more reported cases (ampicillin, amoxicillin, metronidazole, and tetracycline) to those which were associated with OC failure at least once (cephalexin, clindamycin, dapsone, erythromycin, griseofulvin, isoniazid, phenoxymethylpenicillin, telampicillin, and trimethoprim). The physicians recommended that a patient education hand-out include this information as well as directions to report any antibiotic associated diarrhea or breakthrough bleeding to the physician and a reminder to take OCs daily and that OCs are not perfect.

Office dermatologic testing: the Tzanck preparation.

Whether a vesicobullous disease is intraepidermal or subepidermal is often difficult to determine from the clinical examination. The Tzanck preparation can provide clues that aid in the diagnosis of a number of diseases. It is particularly helpful in confirming the diagnosis of herpes infection. This article outlines the materials and steps for performing this valuable test.

Office dermatologic testing: the scabies preparation.

Patients with scabies may present with urticarial, eczematous or excoriated papules, eczematous patches or, occasionally, nodules. It is often difficult to differentiate scabies from eczema, folliculitis, drug eruption or lichen planus. The classically described burrows are often not seen. The scabies preparation, as described in this article, will aid in making the proper diagnosis.

Office dermatologic testing: the KOH preparation.

A potassium hydroxide preparation is used to confirm the diagnosis of a superficial fungal skin infection. Adding black or blue-black ink to the potassium hydroxide solution highlights fungal organisms and distinguishes them from surrounding cellular debris.