Oral contraceptives (also known as "the pill") are highly effective means of preventing pregnancy. Oral contraceptives consist of synthetic forms of two hormones produced naturally in the body: either progestin alone or estrogen and progestin. It is especially important to check with your doctor before combining oral contraceptives with the following: Acetaminophen (Tylenol) Amitriptyline (Elavil) Ampicillin (Principen) Aspirin Atorvastatin (Lipitor) Barbiturates (phenobarbital, Seconal) Carbamazepine (Tegretol) Chloramphenicol (Chloromycetin) Clofibrate (Questran) Clomipramine (Anafranil) Cyclosporine (Neoral, Sandimmune) Dexamethasone Diazepam (Valium) Doxepin (Sinequan) Felbamate (Felbatol) Fluconazole (Diflucan) Glipizide (Glucotrol) Griseofulvin (Fulvicin, Gris-PEG) HIV protease inhibitor drugs such as Crixivan (indinavir) Imipramine (Tofranil) Itraconazole (Sporanox) Ketoconazole (Nizoral) Lorazepam (Ativan) Metoprolol (Lopressor) Modafinil (Provigil) Morphine (MS Contin) Oxazepam (Serax) Oxcarbazepine (Trileptal) Penicillin (Veetids, Pen-Vee K) Phenylbutazone Phenytoin (Dilantin) Prednisolone (Prelone, Pediapred) Prednisone (Deltasone) Primidone (Mysoline) Propranolol (Inderal) Rifabutin (Mycobutin) Rifampin (Rifadin, Rimactane) St. Take high-estrogen pills (0.05 milligrams of estrogen) only if your doctor feels it's necessary. Since the blood's clotting ability may be affected by oral contraceptives, your doctor may take you off them prior to surgery.