The use of growth hormone therapy in Turners originated from a series of studies in the 1980s finding it to substantially increase the height of treated girls, compared to prior adult height predictions and Turners growth charts; treatment with human growth hormone appears to increase expected adult height by approximately 7 cm (3 in) from an otherwise expected norm of 142 cm (4 ft 8 in)–147 cm (4 ft 10 in). In some cases oxandrolone, a steroid with a relatively mild masculinizing effect, may be used alongside growth hormone. The addition of oxandrolone to a Turners treatment regimen adds around 2 cm (1 in) to the final height. Oxandrolone is used particularly often in girls diagnosed later in their growth period, due to the reduced impact of growth hormone alone in this population. However, oxandrolone use runs the risk of delayed breast development, voice deepening, increased body hair, or clitoromegaly. The effects of growth hormone therapy are at their strongest during the first year of treatment and taper off over time. Physical features
In addition to short stature, Turner syndrome is associated with a number of characteristic physical features. These include a webbed neck, a low hairline, a small chin and jaw, a high-arched palate, and a broad chest with wide-spaced nipples. Lymphedema (swelling) of the hands and feet is common at birth and sometimes persistent throughout the lifespan.
The drug has a bioavailability of 90%, and peak plasma concentrations are seen after 2–4 hours. The mean drug half-life is approximately 11 hours. Mexiletine is predominantly metabolised by the liver. The pharmacokinetics of mexiletine are preserved with even moderate to severe renal impairment, but dose adjustment may be required when creatinine clearance falls below 10 mL/minute. Synthesis
Society and culture
Mexiletine is available for human use in the US, and has been reintroduced in the UK as a licensed product, having previously only been available as a named patient import. The drug is sold under the trade name Mexitil for use in arrhythmias and NaMuscla for use in myotonia. Veterinary uses
Mexiletine is available to veterinarians in the US for the treatment of heart disease in dogs and cats. It is commonly used for the treatment of arrhythmogenic right ventricular cardiomyopathy (ARVC) in Boxer dogs in combination with sotalol. References
Further reading
Peck T, Hill S, Williams M, eds. (2004). Pharmacology for Anaesthesia and Intensive Care (2nd ed.). Cambridge University Press. ISBN 0-521-68794-2. External links
"Mexiletine". Drug Information Portal. U.S. National Library of Medicine.