Medical Portal Mediway.com

Medical Specializations, Medical Dictionary


  Molecules
  Diseases
  Books
  Medical Products
  First aid
  Medical Specializations
  Doctors' Listing
  Hospitals
  Pharma/Drug Companies
  Manufacturers of Surgical
  Instruments

  Medical Colleges
  Medical Associations
  Medical Dictionary
  Conferences & Exhibitions
  Image Gallery
  Video Library
  Home
  Contact Us

Medical Specializations


Anaesthesia => Drug => Thalidomide


Thalidomide


Thalidomide, drug which has been shown to cause severe foetal malformations when taken during pregnancy.

Introduced in 1957, thalidomide is a non-barbiturate hypnotic, or sedative, and was thought to be extremely safe, even if overdoses were taken. It was marketed as a drug that was not only suitable for use during pregnancy but actually recommended for this. In 1961 there were simultaneous reports from Sydney, Australia, and Hamburg, in the former West Germany, of newborn babies suffering from phocomelia-an extremely rare malformation. Derived from the Greek for "seal's limbs", phocomelia is a deformity in which the limbs do not form properly, with the long bones in the arms or legs absent. It became apparent that the cause of these abnormalities was the drug thalidomide and that the infants' mothers had been taking the drug during the first three months of pregnancy. Experiments on animals later confirmed that thalidomide could cause such abnormalities. However, experiments on pregnant animals had not been carried out before the drug was licensed-because in the late 1950s these experiments were not thought to be important.

Thalidomide is a teratogen, teratogenesis being the name given to the formation of gross structural abnormalities during foetal development. Teratogenic factors, other examples being rubella (German measles) and X-rays, act during the part of gestation known as organogenesis, which lasts from the 17th to the 60th day of pregnancy. During this period the embryo undergoes structural organization and its skeleton and organs are formed.

The type of deformities caused by thalidomide depended upon the exact timing and duration of its administration. Between days 21 and 22 of gestation, thalidomide caused malformation of the ears and cranial nerve defects; from day 24 to day 27, phocomelia of the arms; from day 28 to 29, phocomelia of the arms and legs; and from day 30 to 36, malformation of the hands and anorectal stenosis (narrowing of the lower intestine).

Renewed research into the effects of the drug has centred on possible other properties, such as its ability to affect immunological processes in the body, particularly in the treatment of Hansen's disease (leprosy) and human immunodeficiency virus infections. Other research efforts are examining whether thalidomide was directly responsible for the foetal malformations and whether it actually prevented the foetuses from being miscarried through an immunological effect.

Thalidomide was withdrawn from use by 1962 and with its removal from circulation the number of children with phocomelia decreased to its previous low levels. The thalidomide disaster has had a profound effect on the ways drugs are tested and registered throughout the world. Before a drug can be licensed for use during pregnancy, specific animal studies to exclude toxic effects on a foetus must be carried out and approved. It is also recommended that, as far as possible, pregnant women should avoid taking any drugs during the first part of their pregnancy, especially during the first trimester (0 to 12 weeks).

It has been estimated that in the former West Germany alone 10,000 children were born with deformities. Only 5,000 of these survived; the others died from other malformations. In the United Kingdom, out of 600 affected children born 400 survived. In the United States the licensing of the drug had been delayed by the Food and Drug Administration and so there were very few cases.

Back