SKYLA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SKYLA (SKYLA).
SKYLA (levonorgestrel-releasing intrauterine system) releases levonorgestrel locally into the uterine cavity, causing thickening of cervical mucus, inhibition of sperm motility, and endometrial thinning, which prevents implantation.
| Metabolism | Levonorgestrel is primarily metabolized by CYP3A4 in the liver. |
| Excretion | Fecal, ~100% (levonorgestrel and metabolites); biliary elimination predominant, with enteric recirculation. Minimal renal excretion (<1% unchanged). |
| Half-life | Terminal half-life approximately 25-26 hours, reflecting slow release from the intrauterine system and ongoing systemic absorption. Steady-state concentrations reached within a few weeks. |
| Protein binding | ~98-99% bound to sex hormone-binding globulin (SHBG) and albumin. High-affinity binding to SHBG. |
| Volume of Distribution | Vd approximately 1.0 L/kg (levonorgestrel), indicating extensive distribution into tissues due to lipophilicity and SHBG binding. |
| Bioavailability | Intrauterine: Essentially 100% local delivery. Oral: Not applicable (Skyla is not oral). Transdermal/other routes: Not applicable. |
| Onset of Action | Intrauterine insertion: Contraceptive effect is immediate if inserted within 7 days of menstrual onset; otherwise, wait 7 days. No systemic onset of action as it is locally acting. |
| Duration of Action | Continuous contraceptive efficacy for up to 5 years post-insertion. Hormone release declines over time but maintains efficacy. Removal restores fertility promptly. |
Levonorgestrel-releasing intrauterine system; one device inserted into uterine cavity, replaced every 5 years.
| Dosage form | SYSTEM |
| Renal impairment | No dose adjustment required; pharmacokinetics unaffected by renal impairment. |
| Liver impairment | Contraindicated in acute liver disease or liver tumors (benign or malignant). For Child-Pugh A or B: no data; use with caution. Child-Pugh C: contraindicated. |
| Pediatric use | Not indicated for use in postmenarchal females under 18 years; data limited. In adolescents 18+ years, same as adults. |
| Geriatric use | Not indicated for use in postmenopausal women; no dose adjustment necessary if used in perimenopausal women. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SKYLA (SKYLA).
| Breastfeeding | Levonorgestrel is excreted into breast milk in small amounts. Milk-to-plasma ratio is approximately 0.63. No adverse effects reported in breastfed infants; however, long-term effects unknown. Skyla is considered compatible with breastfeeding, but caution is advised. |
| Teratogenic Risk | Pregnancy category X. Skyla (levonorgestrel-releasing intrauterine system) is contraindicated in pregnancy due to risk of ectopic pregnancy, fetal exposure to progestin, and potential congenital anomalies. If pregnancy occurs with IUS in situ, there is increased risk of spontaneous abortion, preterm labor, and septic abortion. No trimesters are safe. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Pregnancy or suspected pregnancy","Postpartum endometritis or infected abortion in the past 3 months","Known or suspected uterine or cervical neoplasia","Uterine anomaly distorting the uterine cavity","Acute pelvic inflammatory disease or history of PID (unless there has been a subsequent intrauterine pregnancy)","Postpartum endometritis or infected abortion in the past 3 months","Known or suspected breast cancer","Liver disease or tumor","Hypersensitivity to any component of SKYLA"]
| Precautions | ["Ectopic pregnancy","Pelvic inflammatory disease (PID)","Uterine perforation","Expulsion","Ovarian cysts","Bleeding irregularities","Missed menstrual periods and pregnancy risk","Sepsis","Breast cancer"] |
Loading safety data…
| Fetal Monitoring | Monitor for signs of pregnancy, ectopic pregnancy, and IUS expulsion. Regular follow-up for device placement verification (e.g., ultrasound). Assess for uterine perforation, infection, and bleeding patterns. In pregnancy, immediate removal of IUS is recommended if possible. |
| Fertility Effects | Reversible contraceptive effect. After removal, return to fertility is rapid; 12-month pregnancy rates similar to non-users. No permanent impact on fertility. |