Pyridoxine-induced photosensitivity and hypophosphatasia

Drug-induced phototoxicity: A systematic review

BACKGROUND

Phototoxicity has been attributed to numerous oral drugs over the past 60 years.

OBJECTIVE

Determine the quality of evidence supporting suspected phototoxicity from oral drugs.

METHODS

The MEDLINE and EMBASE databases were searched for all studies that contain original data for drug-induced phototoxicity and were published between May 1959 and December 2016. Study quality was assessed by using a modified Grading of Recommendations, Assessment, Development and Evaluation scale.

RESULTS

The review included 240 eligible studies with a total of 2466 subjects. There were 1134 cases of suspected phototoxicity associated with 129 drugs. Most associations were supported by either very low-quality or low-quality evidence (89.1% of the studies). Medications supported by stronger evidence were vemurafenib, nonsteroidal anti-inflammatory drugs, and antibiotics, specifically, fluoroquinolones and tetracyclines. The most frequently reported drugs were vemurafenib, voriconazole, doxycycline, hydrochlorothiazide, amiodarone, and chlorpromazine. Photobiologic evaluation was performed in only 56 studies (23.3%), whereas challenge-rechallenge was done in 10% of cases.

LIMITATIONS

Only English-language publications were reviewed. Cases of phototoxicity that had been incorrectly categorized as photoallergy would not have been included.

CONCLUSIONS

Most purported associations between oral drugs and phototoxicity are not supported by high-quality evidence. Despite the variable quality of data, clinicians should be aware of the possible consequences of long-term use of culprit drugs.

Safety considerations and potential interactions of vitamins: should vitamins be considered drugs?

OBJECTIVE

To examine adverse effects, adverse events, and potential interactions of vitamins in light of their current prevalence of use, and to discuss whether vitamins should be considered over-the-counter drugs or natural health products/dietary supplements.

DATA SOURCES

We performed a MEDLINE/PubMed search, explored 4 online databases (Medline Plus, Drug Digest, Natural Medicine Comprehensive Database, and the database of the University of Maryland), and examined reference lists of included studies published from 1966 through October 2009.

STUDY SELECTION AND DATA EXTRACTION

The studies were reviewed, with an emphasis on randomized controlled clinical trials. We included articles with the most clinically important information with regard to adverse events and interactions.

DATA SYNTHESIS

Vitamins are used by over one third of the North American population. Vitamins have documented adverse effects and toxicities, and most have documented interactions with drugs. While some vitamins (biotin, pantothenic acid, riboflavin, thiamine, vitamin B(12), vitamin K) have minor and reversible adverse effects, others, such as fat-soluble vitamins (A, E, D), can cause serious adverse events. Two water-soluble vitamins, folic acid and niacin, can also have significant toxicities and adverse events.

CONCLUSIONS

Our recommendation is that vitamins A, E, D, folic acid, and niacin should be categorized as over-the-counter medications. Labeling of vitamins, especially those intended for children and other vulnerable groups, should include information on possible toxicities, dosing, recommended upper intake limits, and concurrent use with other products. Vitamin A should be excluded from multivitamin supplements and food fortificants.

Mutational analysis and functional correlation with phenotype in German patients with childhood-type hypophosphatasia

The tissue-nonspecific alkaline phosphatase (TNSALP) gene from five German family members with childhood-type hypophosphatasia (HOPS) was analyzed using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP)-direct sequencing method. Four novel missense mutations (T51M, R54S, L258P, and R374H) and two that had been described previously (A160T and R206W) were detected in the respective patients. Mutation A160T was detected in 3 distinct patients, and a polymorphism V505A that had been described previously was detected in the same allele as L258P mutation in 1 patient and in 2 fathers whose V505A alleles were not transmitted to the probands. No other mutations were found in 2 patients. Transient expression of the mutant proteins in COS-1 cells showed that the four novel mutations and R206W were severe alleles, whereas A160T was a moderate allele. Analysis of its enzymatic activity and genetic transmission patterns confirmed that V505A was a polymorphism. Immunoprecipitation of the transiently expressed proteins showed that levels of the 80-kDa mature form of the enzyme were diminished or absent with the severe alleles; instead, levels of high-molecular mass disulfide-linked aggregates were increased. These results suggest that in compound heterozygotes, the combination of severe and moderate alleles may combine to cause the mild phenotype seen in childhood-type HOPS.