Pareira

Chondrodendron tomentosum

COMMON NAMES

• Curare
• Pareira

A woody vine often found in trees, pareira has a velvety appearance and may extend up to a foot in length. The stem is gray and furrowed, and it may be partly covered with lichen. Roots are blackish brown, tough, heavy, and knotty. The inside is reddish yellow. Berries are black or scarlet.

Deep in the Amazonian rain forest, an Indian stalks a young deer. The deer hesitates, sniffs the wind. The Indian raises a long blowgun to his lips and with a powerful puff of air, he sends a poison-tipped dart flying. The startled deer leaps into the underbrush, and the hunter follows. He soon finds his prey, paralyzed and dying of asphyxiation.

This primitive scene, played out in one form or another for centuries, may seem far removed from the sterile setting of a modem operating room in North America, where a surgeon performs a delicate abdominal operation. But the two are linked. The connecting thread is the drug curare, extracted from the woody stems of the high-climbing pareira vine..

The first European to testify to the use of curare was a Spanish soldier named Pedro de Cieza de Loon. About 1540 he saw several Indian tribes in what is now Peru, Ecuador, Brazil, and Colombia hunting with arrows whose tips had been dipped in the gummy substance. In 1541 the explorer Francisco de Orellana lost a companion to such an arrow. In 1595 Sir Walter Raleigh took a sample of the poison home to England.

The following centuries saw much lurid sensationalism about the mysterious poison. Speculations about its source ranged from snake venom to boiled ants to rare orchids. Expeditions found tantalizing bits of information: over 20 tribes used curare and all had different formulas; some stored it in pots, some in bamboo tubes, and some in gourds (for a time, these were regarded as the three basic types of curare); some applied it to the tips of darts, some to the detachable heads of arrows, and some to the points of wooden spears; the poison killed by asphyxiating its victims. Still, no one knew exactly what it was, how it was made, or why it worked.

The breakthrough came in 1844, when the French physiologist Claude Bernard found in experimenting with frogs that curare blocks the transmission of nerve impulses from the brain to the muscles, relaxing the muscles to the point of limpness. When chest muscles are affected, breathing stops. Not until the early 20th century, however, was it learned that - although each medicine man seemed to have his own secret formula for curare - all were based on the stems of certain climbing vines, and that among these vines pareira was the most lethal. When the alkaloid, tubocurarine, was finally isolated and proved to be the active muscle relaxant in the vine, modern medicine began to find applications for it. It counters such muscle-contracting poisons as strychnine and tetanus toxin. When used to relax the muscles attached to broken bones, it makes them easier and safer to set. It has been used in therapy for victims of polio and cerebral palsy, and in the treatment of epileptic seizures. Its commonest application is in surgery, where it is given intravenously in conjunction with other anesthetics to relax muscles. As a result, a patient needs less anesthetic.

PARTS USED

Root, stem, bark, leaf.

USES

Pareira is a popular source of curare, the deadly arrow poison used by Amazonian tribes. Many European explorers, including Christopher Columbus and Sir Walter Raleigh, returned from South America with tales of men killed by these"evyll frutes".  A silent killer, curare gave the native peoples an almost supernatural superiority over their gun bearing adversaries. Tubocurarine, a derivative of pareira, has been administered as a lethal injection in capital punishment and euthanasia in countries such as the United States and the Netherlands. It is subject to restrictions in some countries.

Pareira is the only known source of the not-yet-synthesized alkaloid deltatubocurarine, first isolated in 1935. D-tubocurarine is given in small quantities with general anesthesia to produce muscle paralysis; it interferes with nerve impulse transmission at the receptor sites of skeletal muscles. It is also used in shock therapy and in the setting of fractures. Some consider pareira a diuretic and a uterine stimulant, including the Brazilians, who also use it to treat poisonous snakebite.

Pareira's notoriety as a poison hinges on the effect of its toxic derivative entering directly into the bloodstream. Provided there are no cuts or sores in the mouth, pareira is reasonably safe taken orally as a medicinal remedy. The bitter and slightly sweet-tasting roots and stems are mildly laxative, tonic, and diuretic, and also act to induce menstruation. Pareira is chiefly used to relieve chronic inflammation of the urinary tubules. In Brazil, pareira is also used for snake bite, for which an infusion of the root is taken internally while the bruised leaves are applied externally.

HABITAT AND CULTIVATION

Pareira is confined mainly to the Guianas and the Amazon basin. Pareira is also found in the West Indies and other regions of South America. Pareira requires a tropical or a sub- tropical climate.

RESEARCH

Pareira's powerful ability to paralyze has led to its being extensively researched, and it has been adopted by Western medicine. Tubocurarine -one of the many alkaloids within the plant -is now used (as tubocurarine chloride) to paralyze the body's muscles during operations.

CONSTITUENTS

Pareira contains alkaloids, including delta-tubocurarine and L-curarine. Tubocurarine is a potent muscle relaxant.

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