Inclusion Criteria:

• Healthy adult female subject of child bearing potential (including subject with tubal ligation), white origin, who is able to read, to write and fully understand German language
• Aged 18 to 45 years (both inclusive)
• BMI of 18-28 kg/m2 and a body weight of 50-90 kg (both inclusive)
• The subject is required
• To have taken a DRSP/EE- containing OC for at least two dosing cycles
• To agree using reliable non hormonal birth control methods from Day -1 of study Period 1 until the Final Examination (e.g. non-hormonal IUD, double barrier method [e.g. condom with spermicide or diaphragm with spermicide], sexual abstinence). Women with tubal ligation or sterilized partner do not need an additional birth control method
• Willing and able to provide written informed consent after having been informed of the requirements and the restrictions of the study

Exclusion Criteria:

• History of clinically relevant allergy or known hypersensitivity to Neramexane/Memantine/ Amantadine and their derivatives
• Hypersensitivity to Quinine
• History of clinically relevant allergy or known hypersensitivity to any inactive ingredient in any of the used study medications (Neramexane, Yasmin®, Placebo) or tool substance
• History of clinically relevant allergy or known hypersensitivity to DRSP/EE
• Clinically relevant findings on the mammae or genital examination, PAP smear ≥ III
• Any contraindications against the oral contraceptive:
• present or past venous thromboses (deep vein thrombosis, pulmonary embolism);
• present or past arterial thromboses (e.g. myocardial infarction) or their prodromal stages (e.g. angina pectoris and transitory ischaemic attack);
• present or past cerebrovascular insult;
• presence of a serious risk factor or several risk factors for an arterial thrombosis: diabetes mellitus with vascular changes, severe hypertension, severe lipid metabolism disturbance;
• known or suspected genetic or acquired predisposition for venous or arterial thromboses like APC resistance,
• known or suspected genetic lack of antithrombin III, lack of protein C, lack of protein S, hyperhomocysteinaemia and antiphospholipid antibodies (anticardiolipin antibodies, lupus anticoagulants);
• present or past pancreatitis if this is accompanied by severe hypertriglyceridaemia;
• present or past severe hepatic disease as long as the liver function tests have not normalized;
• severe renal insufficiency or acute renal failure;
• present or past hepatic tumors (benign or malign);
• known or suspected sexual hormone dependent, malign tumors (e.g. of the genital organs or the mamma);
• diagnostic not clarified vaginal bleedings;
• anamnesis of migraine with focal neurologic symptoms;
• known hereditary angioedema
• Exposure to another investigational agent within the last two months before Day 1 of Period 1