Doxycycline - Cautions and Side Effects

Cautions and Side Effects

Cautions and side effects are similar to those of other members of the tetracycline antibiotic group. However, the risk of photosensitivity skin reactions is of particular importance for those intending long-term use for malaria prophylaxis, because it can cause permanent sensitivity and thin skin, which may lead to sun damage.

An erythematous rash in sun-exposed parts of the body has been reported to occur in 7.3–21.2% of persons taking doxycycline for malaria prophylaxis. One study examined the tolerability of various malaria prophylactic regimens and found doxycycline did not cause a significantly higher percentage of all skin events (photosensitivity not specified) when compared with other antimalarials. The rash resolves upon discontinuation of the drug.

Unlike some other members of the tetracycline group, it may be used in those with renal impairment.

Previously, doxycycline was believed to impair the effectiveness of many types of hormonal contraception due to CYP450 induction. Recent research has shown no significant loss of effectiveness in oral contraceptives while using most tetracycline antibiotics (including doxycycline), although many physicians still recommend the use of barrier contraception for people taking the drug to prevent unwanted pregnancy.

Taking doxycycline with food and dairy products may decrease the amount of medication absorbed. The combination of doxycycline with dairy, antacids, calcium supplements, iron products, and laxatives containing magnesium is not inherently dangerous, but any of these foods and supplements may decrease doxycycline's effectiveness.

Doxycycline, like all tetracyclines, is not approved for general use in children, but specific exceptions are made for potentially fatal illnesses where the benefits outweigh the risks and there are few or no other alternatives, such as with Rocky Mountain spotted fever and anthrax. It is not recommended for use in pregnant women and underweights (<45 kg).

Expired tetracyclines or tetracyclines allowed to stand at a pH less than 2 are reported to be nephrotoxic due to the formation of a degradation product, anhydro-4-epitetracycline causing Fanconi syndrome. In the case of doxycycline, the absence of a hydroxyl group in C-6 prevents the formation of the nephrotoxic compound. Nevertheless, tetracyclines and doxycycline itself have to be taken with precaution in patients with kidney injury, as they can worsen azotemia due to catabolic effects.