* initiation of pharmacological treatment or change of dose within the 30 days preceding the present study * contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine * use of potassium channel blockers within the last 3 months * concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) * acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) * acute cerebrovascular condition * history of seizures * risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) * renal impairment * history of malignant cancers * walking problems (e.g. due to dizziness) * other clinically significant concomitant disease states that could pose a safety risk (e.g. hepatic dysfunction, cardiovascular disease, urinary tract infection) * bradycardia \< 50/min during clinical examination * clinically significant laboratory or ecg abnormality that could be a safety issue in the study * known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) * drug or alcohol abuse * inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant * participation in another study with an investigational drug within the 30 days preceding and during the present study * enrolment of the investigator, his/her family members, employees and other dependent persons * pregnancy or breast feeding * intensive care treatment due to covid-19 infection. exclusion criteria concerning tms measurement * metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) * implanted neurostimulator (e.g., dbs, epidural/subdural, vns) * cardiac pacemaker or intracardiac lines * medication infusion device * piercings in the head area, pivot teeth (retainers are no exclusion criterion) * tattoos (in the head area) with metallic inks or newly stung tattoos (\< 3 months), as newly stung tattoos can be damaged by a magnetic field; * condition after neurosurgery * hearing problems or tinnitus * not able to sit still due to tremor, tics, itching * history of repeated syncope * head trauma diagnosed as concussion or associated with loss of consciousness * diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family * tms in the past showing problems * mri in the past showing problems * surgical procedures to spinal cord * spinal or ventricular derivations tms measurement is optional. if a participant is eligible for the study, but prefers not to undergo tms measurement or meets one or more exclusion criteria for tms measurement, the participant can nevertheless be included in the study without rmt measurement using tms.

* initiation of pharmacological treatment or change of dose within the 30 days preceding the present study * contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine * use of potassium channel blockers within the last 3 months * concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) * acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) * acute cerebrovascular condition * history of seizures * risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) * renal impairment * history of malignant cancers * walking problems (e.g. due to dizziness) * other clinically significant concomitant disease states that could pose a safety risk (e.g. hepatic dysfunction, cardiovascular disease, urinary tract infection) * bradycardia \< 50/min during clinical examination * clinically significant laboratory or ecg abnormality that could be a safety issue in the study * known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) * drug or alcohol abuse * inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant * participation in another study with an investigational drug within the 30 days preceding and during the present study * enrolment of the investigator, his/her family members, employees and other dependent persons * pregnancy or breast feeding * intensive care treatment due to covid-19 infection. exclusion criteria concerning tms measurement * metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) * implanted neurostimulator (e.g., dbs, epidural/subdural, vns) * cardiac pacemaker or intracardiac lines * medication infusion device * piercings in the head area, pivot teeth (retainers are no exclusion criterion) * tattoos (in the head area) with metallic inks or newly stung tattoos (\< 3 months), as newly stung tattoos can be damaged by a magnetic field; * condition after neurosurgery * hearing problems or tinnitus * not able to sit still due to tremor, tics, itching * history of repeated syncope * head trauma diagnosed as concussion or associated with loss of consciousness * diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family * tms in the past showing problems * mri in the past showing problems * surgical procedures to spinal cord * spinal or ventricular derivations tms measurement is optional. if a participant is eligible for the study, but prefers not to undergo tms measurement or meets one or more exclusion criteria for tms measurement, the participant can nevertheless be included in the study without rmt measurement using tms.

initiation of pharmacological treatment or change of dose within the 30 days preceding the present study contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states that could pose a safety risk (e.g. hepatic dysfunction, cardiovascular disease, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding intensive care treatment due to covid-19 infection. exclusion criteria concerning tms measurement metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings in the head area, pivot teeth (retainers are no exclusion criterion) tattoos (in the head area) with metallic inks or newly stung tattoos (< 3 months), as newly stung tattoos can be damaged by a magnetic field; condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations tms measurement is optional. if a participant is eligible for the study, but prefers not to undergo tms measurement or meets one or more exclusion criteria for tms measurement, the participant can nevertheless be included in the study without rmt measurement using tms.

initiation of pharmacological treatment or change of dose within the 30 days preceding the present study contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states that could pose a safety risk (e.g. hepatic dysfunction, cardiovascular disease, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding intensive care treatment due to covid-19 infection. exclusion criteria concerning tms measurement metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings in the head area, pivot teeth (retainers are no exclusion criterion) tattoos (in the head area) with metallic inks or newly stung tattoos (< 3 months), as newly stung tattoos can be damaged by a magnetic field; condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations tms measurement is optional. if a participant is eligible for the study, but prefers not to undergo tms measurement or meets one or more exclusion criteria for tms measurement, the participant can nevertheless be included in the study without rmt measurement using tms.

initiation of pharmacological treatment or change of dose within the 30 days preceding the present study contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states that could pose a safety risk (e.g. hepatic dysfunction, cardiovascular disease, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding intensive care treatment due to covid-19 infection. exclusion criteria concerning tms measurement metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings in the head area, pivot teeth (retainers are no exclusion criterion) tattoos (in the head area) with metallic inks or newly stung tattoos (< 3 months), as newly stung tattoos can be damaged by a magnetic field; condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations

initiation of pharmacological treatment or change of dose within the 30 days preceding the present study contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states that could pose a safety risk (e.g. hepatic dysfunction, cardiovascular disease, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding intensive care treatment due to covid-19 infection. exclusion criteria concerning tms measurement metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings in the head area, pivot teeth (retainers are no exclusion criterion) tattoos (in the head area) with metallic inks or newly stung tattoos (< 3 months), as newly stung tattoos can be damaged by a magnetic field; condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations

medical treatment of long-covid-symptoms besides nonsteroidal noninflammatory drugs contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) intake of psychoactive drugs (e.g. benzodiazepines, antidepressants, neuroleptics) intake of oral and inhalational antihistaminics and/or steroids acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states (e.g. hepatic dysfunction, cardiovascular disease, diabetes, asthma, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse smoking (>3 cigarettes per day) inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding experiencing a syncope during basal rmt measuring hospitalization due to covid-19 infection exclusion criteria concerning tms measurement metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings in the head area, pivot teeth (retainers are no exclusion criterion) tattoos (in the head area) with metallic inks or newly stung tattoos (< 3 months), as newly stung tattoos can be damaged by a magnetic field; condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations

medical treatment of long-covid-symptoms besides nonsteroidal noninflammatory drugs contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) intake of psychoactive drugs (e.g. benzodiazepines, antidepressants, neuroleptics) intake of oral and inhalational antihistaminics and/or steroids acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states (e.g. hepatic dysfunction, cardiovascular disease, diabetes, asthma, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse smoking (>3 cigarettes per day) inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding experiencing a syncope during basal rmt measuring hospitalization due to covid-19 infection exclusion criteria concerning tms measurement metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings in the head area, pivot teeth (retainers are no exclusion criterion) tattoos (in the head area) with metallic inks or newly stung tattoos (< 3 months), as newly stung tattoos can be damaged by a magnetic field; condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations

medical treatment of long-covid-symptoms besides nonsteroidal noninflammatory drugs contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) intake of psychoactive drugs (e.g. benzodiazepines, antidepressants, neuroleptics) intake of oral and inhalational antihistaminics and/or steroids acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states (e.g. hepatic dysfunction, cardiovascular disease, diabetes, asthma, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse smoking (>3 cigarettes per day) inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding experiencing a syncope during basal rmt measuring hospitalization due to covid-19 infection. metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings, pivot teeth (retainers are no exclusion criterion) tattoos (head area) less than 3 months old or older than 20 years condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations

medical treatment of long-covid-symptoms besides nonsteroidal noninflammatory drugs contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to 4-aminopyridine use of potassium channel blockers within the last 3 months concomitant treatment with oct 2 inhibitors and -substrates (e.g. cimetidine, propranolol) intake of psychoactive drugs (e.g. benzodiazepines, antidepressants, neuroleptics) intake of oral and inhalational antihistaminics and/or steroids acute or chronic psychiatric disorder (e.g. major depression, psychosis, somatoform disorder, suicidal tendency) acute cerebrovascular condition history of seizures risk of lowered seizure threshold (due to e.g. sleep deprivation, withdrawal of alcohol after alcohol abuse) renal impairment history of malignant cancers walking problems (e.g. due to dizziness) other clinically significant concomitant disease states (e.g. hepatic dysfunction, cardiovascular disease, diabetes, asthma, urinary tract infection) bradycardia < 50/min during clinical examination clinically significant laboratory or ecg abnormality that could be a safety issue in the study known or suspected non-compliance (e.g. missing more than one dose of study medication per intervention phase) drug or alcohol abuse smoking (>3 cigarettes per day) inability to follow the procedures of the study, e.g. due to language or psychological problems of the participant participation in another study with an investigational drug within the 30 days preceding and during the present study enrolment of the investigator, his/her family members, employees and other dependent persons pregnancy or breast feeding experiencing a syncope during basal rmt measuring hospitalization due to covid-19 infection. metal in the brain, skull or elsewhere in the body (e.g., splinters, fragments, clips, etc.) implanted neurostimulator (e.g., dbs, epidural/subdural, vns) cardiac pacemaker or intracardiac lines medication infusion device piercings, pivot teeth (retainers are no exclusion criterion) tattoos (head area) less than 3 months old or older than 20 years condition after neurosurgery hearing problems or tinnitus not able to sit still due to tremor, tics, itching history of repeated syncope head trauma diagnosed as concussion or associated with loss of consciousness diagnosis of epilepsy, or a convulsion or a seizure in the past of the participant or his family tms in the past showing problems mri in the past showing problems surgical procedures to spinal cord spinal or ventricular derivations