Hormonal contraceptives have been associated with retinal thrombosis. Although this is generally believed to be related to the estrogen component, patients should be monitored carefully for the development of ocular lesions, and levonorgestrel capsules should be removed if any unexplained visual disturbance occurs. Altered glucose tolerance secondary to decreased insulin sensitivity has been reported during hormonal contraceptive therapy. Although the effects appear to be minimal during therapy with progestins, levonorgestrel implants should be used cautiously in patients with diabetes mellitus. Levonorgestrel is relatively contraindicated in hyperlipidemia because some progestins increase LDL concentration, exacerbating the condition, particularly with long-term use.
Hormonal contraceptives can cause fluid retention.
Levonorgestrel implants should be prescribed cautiously in patients with congestive heart failure, nephrotic syndrome, or other renal disease. Drugs that can induce hepatic enzymes can accelerate the rate of metabolism of hormonal contraceptives. Pregnancy has been reported during levonorgestrel therapy in patients receiving phenytoin or carbamazepine concurrently. Since the dosage of levonorgestrel implants cannot be modified, another form of contraception should be considered in patients requiring therapy with carbamazepine or phenytoin. Barbiturates and rifampin also can induce hepatic enzymes, so levonorgestrel should be used cautiously in patients receiving these drugs.