Disposition of pilocarpine in the pigmented rabbit eye

The disposition of pilocarpine in the pigmented rabbit eye following instillation of a pilocarpine solution was studied using radiotracer techniques. The results suggest that a topically applied pilocarpine solution was removed as efficiently from the tear chamber of the pigmented rabbit as from that of albino rabbit. Nevertheless, a larger fraction of the applied dose was recovered in the pigmented rabbit eye, possibly due to the combined effect of improved corneal permeability, metabolism of the drug in the cornea, and metabolism and binding of the drug in the iris-ciliary body. Based on the area under the drug concentration vs time curve, about 10 times as much pilocarpine was found in the iris-ciliary body of the pigmented than the albino rabbit. Despite this drug accumulation in the iris-ciliary body, which presumably derived its drug supply from the aqueous humor, the pilocarpine concentration in the aqueous humor of the pigmented rabbit was virtually indistinguishable from that in the albino rabbit.