Unusual side-effects in patients receiving doxycycline

Drug-induced photosensitivity: culprit drugs, management and prevention

Photo-induced drug eruptions are cutaneous adverse events due to exposure to a drug and either ultraviolet or visible radiation. Based on their pathogenesis, they can be classified as phototoxic or photoallergic drug eruptions, although in many cases it is not possible to determine whether a particular eruption is due to a phototoxic or photoallergic mechanism. In this review, the diagnosis, prevention and management of drug-induced photosensitivity are discussed. Diagnosis is based primarily on the history of drug intake and the clinical appearance of the eruption, primarily affecting sun-exposed areas of the skin. Phototesting and photopatch testing can be useful adjuncts in making a diagnosis. The mainstay of management is prevention, including informing patients of the possibility of increased sun sensitivity and the use of sun protective measures. However, once the eruption has occurred, it may be necessary to discontinue the culprit medication and treat the eruption with a potent topical corticosteroid. Drugs that have been implicated in causing photosensitive eruptions are reviewed. Tetracycline, doxycycline, nalidixic acid, voriconazole, amiodarone, hydrochlorothiazide, naproxen, piroxicam, chlorpromazine and thioridazine are among the most commonly implicated medications. We review the medical literature regarding evidence for the culpability of each drug, including the results of phototesting, photopatch testing and rechallenge testing.

Safety of doxycycline and minocycline: a systematic review

OBJECTIVE

The goal of this review was to summarize the available literature covering the safety profiles of oral doxycycline and minocycline.

METHODS

Scientific literature published between 1966 and August 2003 was searched using the MEDLINE, EMBASE, and Biosis databases (search terms: minocycline or doxycycline, each paired with adverse reaction, adverse event, and side effect, and doxycycline or minocycline with the limits English language, human, and clinical trials). Safety information was collected from case reports and clinical trials. Adverse event (AE) rates in the United States were calculated by comparing data from the MedWatch AE reporting program used by the US Food and Drug Administration (FDA) with the number of new prescriptions dispensed for each drug from January 1998 to August 2003.

RESULTS

Between 1966 and 2003, a total of 130 and 333 AEs were published in case reports of doxycycline and minocycline, respectively. In 24 doxycycline clinical trials (n = 3833) and 11 minocycline trials (n = 788), the ranges in incidence of AEs were 0% to 61% and 11.7% to 83.3%, respectively. Gastrointestinal AEs were most common with doxycycline; central nervous system and gastrointestinal AEs were most common with minocycline. From January 1998 to August 2003, the FDA MedWatch data contained 628 events for doxycycline and 1099 events for minocycline reported in the United States. Approximately 47,630,000 doxycycline and 15,234,000 minocycline new prescriptions were dispensed in the United States during that period, yielding event rates of 13 per million for doxycycline and 72 per million for minocycline, based on FDA data.

CONCLUSIONS

Between 1998 and 2003, doxycycline was prescribed 3 times as often as minocycline. The incidence of AEs with either drug is very low, but doxycycline had fewer reported AEs. Although more head-to-head clinical trials are needed for a direct comparison of AE frequency, these preliminary data from separate reports suggest the possibility that AEs may be less likely with doxycycline than minocycline.

Acne: Systemic treatment

Acne vulgaris is a disease affecting mostly adolescents and young adults that, when severe, has the potential to result in scarring and permanent disfigurement. Systemic treatment is necessary to prevent significant psychological and social impairment in these patients.(1) Significant inflammatory and nodulocystic acne is usually recalcitrant to topical treatment, whereas uncommon acne variants, such as acne fulminans, pyoderma faciale, and acne conglobata, need to be promptly and effectively controlled. In all of these circumstances, systemic agents are indispensable. The choices include oral antibiotics, isotretinoin, and hormonal treatment (Table 1).

Chronic intoxication by doxycycline use for more than 12 years

We report the clinical case of a 12-years' intoxication by doxycycline. A patient with a depersonalization and derealization syndrome took 1 g doxycycline per day. In addition to hepatocellular necrosis with cholestasis, nephrotoxicity, leukopenia, anaemia and skin hyperpigmentation he suffered from hitherto unreported adverse cardiac events as intermittent supraventricular tachycardia and sporadic Wenckebach heart block. Despite a long period of self-medication these side-effects were reversible.

Phototoxic eruptions due to doxycycline--a dose-related phenomenon

The tetracycline group of antibiotics still remains the most successful oral treatment for acne. They are relatively free from side-effects apart from the occasional gastrointestinal upset or vaginal candidosis. Rarer side-effects include drug rashes, pigmentation with minocycline and a light-sensitive eruption with doxycycline. The incidence of light-sensitive rashes with doxycycline at a dose of 100 mg daily, is in the order of 3%. Acne does not always respond to conventional regimens of antibiotics and higher dosages may be required. We report a highly significant incidence of light-sensitive eruptions in patients receiving doxycycline at a daily dose of 150 mg or above.