“On the rate of absorption from intramuscular tissue,” with demonstrations

Abstract

In physiology no distinction is made between absorption from the subcutaneous tissue and absorption from muscles. In experimental infection and immunity, injections of virulent toxic and antitoxic materials are being extensively employed, but intramuscular injection has not yet even been thought of. In therapeutics it is practised promiscuously, and for the reason, as pharmacologists and clinicians expressly state, that it gives less pain and causes less frequently the formation of abscesses.

The authors came upon the observation that absorption from the muscles is incomparably more rapid and efficient than from the subcutaneous tissue and tested the matter with several substances. With suprarenal extract, it was tested in three ways.

1. By the effect upon blood-pressure.—A subcutaneous dose of 0.6 c.c. adrenalin or less per kilo (rabbit) exerts no effect, and the variable effects of larger doses consist in a rise of pressure of from about 10 mm. to 20 mm. of mercury, which sets in late and develops slowly. An intramuscular injection of 0.5 c.c or 0.4 c.c. per kilo, or even less, invariably causes, on the other hand, a considerable rise of pressure, which sets in after a very short latent period and reaches its maximum in a few seconds. The curve obtained after intramuscular injection is very similar to that after an intravenous injection. The increase has been as high as 50 mm. or 60 mm. of mercury and may go even higher. The course of the curve is frequently interrupted by “vagus pulses.”

2. By the effect upon the pupil on the side from which the superior cervical ganglion had been previously removed.— An intravuscular dose of 0.5 c.c. or 0.4 c.c. of adrenalin per kilo causes dilation of the pupil in less than a minute, while such a dose given subcutaneously rarely produces any effect. The effect of a larger subcutarjeous dose sets in only after 10 or 15 minutes.