Release rates of levonorgestrel from Silastic capsules, homogeneous rods and covered rods in humans.
Three forms of subdermal implants containing levonorgestrel are described. These are: capsules, in which the powdered drug is sealed inside of lengths of Medical Grade Silastic tubing; homogeneous rods, in which the drug is uniformly dispersed in Silastic 382 Medical Grade Elastomer; and covered rods, in which a core rod of drug and filler-free polydimethylsiloxane polymer (50:50, Wt:Wt) are sealed inside thin-walled Silastic tubing. Long-term in vivo release rates from human subjects are presented; 6.5 years for capsules, 3.6 years for homogeneous rods and 4 years for covered rods. Sets of six capsules release a decreasing amount of drug through the first few hundred days in situ and after 500 days a fairly constant rate of about 35 micrograms per day is released (2 micrograms/cm). Homogeneous rods deliver a continuously declining amount of drug during the entire time studied. In the first 100 days the release averages 136 micrograms per day from a set of three 3-cm rods (15 micrograms/cm), gradually declining to 30 micrograms per day (3.3 micrograms/cm) from day 800 to day 1300. The covered rods deliver at a constant rate of 17.5 micrograms per day for a 3-cm rod (5.83 micrograms/cm) through 4 years.
D002214:Capsules; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage / Q000378:metabolism; D004129:Dimethylpolysiloxanes; D004343:Drug Implants; D005260:Female; D006801:Humans; D016912:Levonorgestrel; D009644:Norgestrel / Q000008:administration & dosage* / Q000378:metabolism; D012828:Silicones
D002214:Capsules; D003277:Contraceptives, Oral, Combined; D004129:Dimethylpolysiloxanes; D004343:Drug Implants; D012828:Silicones; D009644:Norgestrel; D016912:Levonorgestrel