Tetracyclines phototoxic reactions

Phototoxic reactions are most frequent with demeclocycline, and occur less frequently with the other tetracyclines minocycline is least likely to cause phototoxic reactions. 

Drugs that are likely to cause phototoxic reactions are amiodarone, nalidixic acid, various NSAIDs, phenothiazines (especially chlorpromazine), and tetracyclines (particularly demedocydine). 

Gastrointestinal reactions that may occur during tetracycline administration include nausea, vomiting, diarrhea, epigastric distress, stomatitis, and sore throat. Skin rashes also may be seen. A photosensitivity (phototoxic) reaction may be seen witli tliis group of dni, manifested by an exa rated sunburn reaction when the skin is exposed to sunlight even for brief periods. Demeclocychne seems to cause the most serious photosensitivity reaction, whereas minocycline is least likely to cause this type of reaction. 

The answer is c. (Hardman, pp 1134-1135.) Hematologic toxicity is by far the most important adverse effect of chloramphenicol The toxicity consists of two types (1) bone marrow depression (common) and (2) aplastic anemia (rare) Chloramphenicol can produce a potentially fatal toxic reaction, the gray baby syndrome, caused by diminished ability of neonates to conjugate chloramphenicol with resultant high serum concentrations. Tetracyclines produce staining of the teeth and phototoxicity... 

Phototoxicity occurs when skin exposed to sunlight, especially in the UVA region of 320 to 400 nm, reddens and develops blisters as a consequence of the presence of certain chemical species. The phototoxic chemical species that result in such reactions are ones to which an individual is exposed either directly on the skin or systemically. These compounds absorb ultraviolet radiation and, like the porphyrins discussed above, enter excited states interacting with 02 to generate destructive oxidant species and free radicals. Numerous chemical species, including furocoumarins, polycyclic aromatic hydrocarbons, tetracyclines, and sulfonamides, can be phototoxic. 

Skin rashes are relatively common with flnoroqninolones. A retrospective cohort stndy in patients in general practice in the Netherlands focused on the nse of antibacterial agents and the occnrrence of adverse cntaneons events covered 469 505 consnltations with 87 475 patients, of whom 13 679 received prescriptions for antibiotics (57). After adjnstment for age, sex, and co-medications, the incidence density ratio (incidence density per 1000 exposed days) for varions gronps of antibacterial agents was as follows tetracyclines 1.0, macrohdes 1.1, flnoroqninolones 2.8, penicillins 2.9, and co-trimoxazole 4.4 (57). No details of the types of skin reactions were given, and it is therefore possible that phototoxic events were inclnded. Compared with other stndies, the reported rate of antibiotic-associated adverse cntaneons events in this ontpatient popnlation was rather low. 

A number of the tetracycline derivatives are phototoxic. In one study, chlortetracycline, doxycycline, and dimethylchlortetracycline treatment of normal human skin fibroblasts resulted in total cell death within 14 days when co-administered with UVA. A dimethylchlortetracycline and UVA cotreatment also showed a strong photosensitizing effect in a 7-day exposure study. These results, too, are consistent with clinically reported reactions in humans J15l... 

For example, tetracycline (506), a broad-spectrum antibiotic, and its derivatives are known to induce phototoxic or photoallergic reactions that involve photosensitization of biomolecules by the drug or the formation of one or more photoproducts and their subsequent photoreactions.1383 Singlet oxygen is probably involved. 

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