The objective of the study was to evaluate the efficacy, safety and tolerability of a single peroral dose of 0.5 g and 1.0 g metamizol relative to placebo and 1.0 g acetylsalicylic acid in 2 episodes of moderate tension headache.

Inclusion Criteria:

• Male and female patients between 18 and 65 years old
• Moderate episodic tension headache according to International Headache Society (I.H.S.) classification 2.1 (2.1.1 and 2.1.2) for at least one year
• At least two episodes of tension headache per month in the last three months prior to enrolment into this trial
• The episodes of tension headaches were usually treated by the patient successfully with a non-opioid-analgesic
• First episodic headache occurred at an age under 50 years
• Written informed consent according to Good Clinical Practice (GCP) and local regulations
• The patient was able to fill in the Patient's Diary

Exclusion Criteria:

• The patient usually needs for successful treatment of tension headache "Over The Counter" (OTC) analgesic in doses exceeding the doses tested here
• The patient takes an OTC-analgesic normally at the first signs of an episode of tension headache
• The patient has more than 15 episodes of tension headache per month
• Female patients whose episodic tension headache is strongly correlated with the start of hormonal contraception
• Concomitant treatment with (non-) prescriptional analgesics
• Pre- (less than 4 weeks prior to inclusion in this trial) and/or concomitant treatment with an antidepressive and/or antipsychotic drug
• Pre- (less than 2 weeks prior to inclusion in this trial) and/or concomitant treatment with any drug such as NSAIDs (Non-Steroidal Anti Inflammatory Drugs), propanolol, metroprolol, flunarizin, cyclandelate, valproic-acid, serotonergic antagonists, ergotamine, dihydroergotamines and benzodiazepines that may influence the headache symptomatology
• Use of benzodiazepines in the previous 24 hours to the administration of the study drug. Occasional use of benzodiazepines - up to 3 per week - is allowed
• Use of any drug with analgesic properties in the previous 24 hours to the administration of the study drug
• Concomitant treatment with any drug containing ASA and/or metamizol
• Concomitant treatment with anticoagulants such as heparin or coumarin-derivatives
• Alcohol and drug abuse according to DSM-IV (Diagnostic and Statistical Manual of Mental Disorders )
• Female patients in child-bearing age not using adequate means of birth control
• Pregnancy and/or lactation
• Gastrointestinal ulcers
• Liver and/or renal disease
• Bronchial asthma
• Relevant allergy or known hypersensitivity to the investigational drugs, its excipients and/or to other NSAIDs
• Participation in another clinical trial within the last 4 weeks and concurrent participation in another clinical trial
• Patients with active gastroesophageal flux disease (Amendment number 1)
• Concomitant treatment with analgesics or any other drug that may have influenced the headache symptomatology - including metamizol or ASA -, was referred to its use during the headache episodes under evaluation. As long as appropriate wash-out periods were respected, analgesics were allowed in between the episodes of tension headache (TH) and their use as a rescue medication did not lead to the exclusion of the patient (Amendment number 2)