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Amoxil (amoxicillin) Linked to Tooth Enamel Defects

October 5, 2005

A longstanding and widely used pediatric antibiotic, Amoxil (amoxicillin) has been found potentially to interfere with normal development of tooth enamel if administered when a child is aged 3-5 months, according to researchers at the University of Iowa.

The recent study was published in the October issue of Archives of Pediatric and Adolescent Medicine and reported by MedPage Today on 3 October.

Based on a longitudinal study of the effects of fluoride on tooth development, the results of the study by Liang Hong, DDS, PhD, and colleagues at the University of Iowa "highlight the need to use antibiotics judiciously, particularly during infancy," according to Hong.

Researchers involved in the trial noted that it has several limitations, including a relative lack of children not treated with the antibiotic, further research is required before the study can be deemed conclusive.

The association between Amoxil and fluorosis (a form of enamel hypomineralization caused by high doses of fluoride and resulting in mottled tooth enamel) on some early-erupting permanent teeth"holds implications for both dental and medical practice if it holds up," Paul Casamassimo, DDS, of the Ohio State University College of Dentistry in Columbus, reported to MedPage Today.

Recent findings by Dr. Hong and colleagues may be "another clue as to why some children get fluorosis and others do not," Dr. Casamassimo said in an accompanying editorial, "but much more study remains to be done before we put away the prescription pads or clear the pharmacy shelves."

Dr. Casamassimo added that, although fluorosis is one of the most common forms of developmental enamel defects, it is not fully understood.

Study Plan & Results

The Iowa Fluoride Study involved 1,390 participants at birth from eight Iowa hospitals. Of those children, 579 underwent examination of early-erupting permanent teeth at approximately age nine years, at which time their teeth were assessed for fluorosis using the Fluorosis Risk Index.

From birth to 32 months, these children's fluoride intake and use of Amoxil (also sold under the brand names Trimox and Wymox) were determined by regular questionnaires completed by their parents.

The study found that:

  • By age 12 months, 75% of the children had received Amoxil, and by age 32 months, 91% had received it.
  • When examined at age nine, 24% of the children had fluorosis on both maxillary central incisors.
  • Amoxil use at the age of 3-6 months significantly increased the fluorosis risk on the maxillary central incisors. (The relative risk was 2.04, with a 95% confidence interval ranging from 1.49 to 2.78.)
  • After adjusting for fluoride intake and otitis media, fluorosis risk on the maxillary central incisors remained significant. (The relative risk became 2.04, with a 95% confidence interval ranging from 1.2 to 2.78.)

Dr. Hong and colleagues cautioned that the study has several limitations, including the fact that only 8.2% of the children in the study had received Amoxil by age by 32 months. Moreover, much data was collected from questionnaires, without direct verification.

The researchers suggested that animal studies be undertaken to try to duplicate the effect experimentally.

Another issue that calls the study's results into question is the fact that fluorosis affected children long before Amoxil, according to Casamassimo, "which raises some skepticism as to the validity of these findings."

Casamassimo also noted that from birth to age six months, children are prone to infection that is often accompanied by fever, and it is possible that the combination of fever and high fluoride levels may cause fluorosis, possibly exacerbated by Amoxil. Even so, confirming these facts may not affect prescribing patterns, which are already showing a trend toward prescribing fewer antibiotics.

Antibiotic Linked to Incomplete Development of Tooth Enamel, MedPage Today, 3 October 2005.
Association of Amoxicillin Use During Early Childhood With Developmental Tooth Enamel Defects, Liang Hong et al., Archives of Pediatric and Adolescent Medicine, volume 159, pages 943-948.

Posted: October 2005