Following the observation that an aqueous solution derived from the pitcher plant was of value in relieving pain of neuralgic origin, the drug was used on a series of several thousand cases, and it became apparent that the preparation acted through its effect on sensory nerves, relieving neuralgic pain without change in skin sensation and having no effect on motor nerves. Bates and Judovich state¹: "In no instance has there been any motor weakness following injection of peripheral nerves, nor loss of touch, pressure, pinprick and temperature sensibility." Controls with procaine, saline and water showed prolonged duration of effect in favor of the pitcher plant preparation. Toxicity tests revealed that it was harmless and no evidence of tissue coagulation or sclerosis could be found. As stated by Bates,² "Controls of novocaine, saline and water were used, and the results recorded. The key numbers of these various ampoules were changed several times, and on analysis in each series, it was found that SARAPIN produced prolonged relief in contrast to fleeting or negative results with the other solutions. In a number of instances, patients who had been injected with novocaine, with only a short period of relief of pain, obtained prolonged relief by a subsequent injection of pitcher plant distillate."

In an attempt to explain this action, the cathode ray oscillograph has been used to investigate the effect of SARAPIN on the action potentials of the saphenous nerve of the cat³. The nerve was mounted in a nerve chamber in an atmosphere of 5 percent carbon dioxide and 95 percent oxygen and maintained at a temperature of 37.5^o C while being bathed in the solution under examination. Recordings made of the action potentials showed that after about five minutes immersion in Sarracenia distillate, the maximal A spike was somewhat reduced while the C fiber potential was completely obliterated.

Early workers, in an attempt to discover the exact nature of the volatile base obtained in the distillation of Sarracenia root, reported the only identifiable product to be the ammonium ion. Pharmacologic investigations which followed disclosed that aqueous solutions containing ammonium ions did possess activity closely related to that of SARAPIN.

In a clinical study involving eight cases of sciatic pain, injection at the sciatic notch with ammonium salts produced no change in surface temperature as determined by thermo-couple readings before and after infiltration.1 Normal skin sensation and reflexes were preserved while the pain and hyperalgesia disappeared. Following the injections, the needles were left in place for twenty minutes, then 10 cc. of a 2 percent solution of procaine hydrochloride were injected. Within two to three minutes there occurred a rise in skin temperature of the extremities, numbness of the extremities and loss of the Achilles reflex, indicating that the needles were correctly placed. This observation is extremely important as indicative of the fact that the ammonium ion has the ability to exert a selective action not possible with procaine.

However, in the light of subsequent investigations involving a comparison of the action of the two solutions (ammonium sulfate and Pitcher Plant distillate) on nerve impulses as shown by the cathode ray oscillograph, it has been concluded that the activity of SARAPIN is due only in part to its content of ammonium ions. Studies on the isolated saphenous nerve of the cat have shown that complete obliteration of the C fiber potentials, accompanied by only slight reduction of the maximal A spike, is possible with Pitcher Plant distillate containing the equivalent of less than five-tenths of a milligram of ammonium sulfate per cubic centimeter; similar studies have shown that a concentration of ten milligrams (20 times as much) of pure ammonium sulfate per cubic centimeter was required to produce comparable effects and, at this concentration, the safety of use becomes questionable. For want of a better explanation it has been theorized that the Pitcher Plant distillate (SARAPIN) contains an infinitesimal and unidentifiable biological antagonist potentiating the action of the ammonium ion.

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