Randomization service for multicenter clinical trials

The Randomizer provides a self-serve, easy to use, secure and 24/7 randomization service (IWRS) for multicenter clinical trials.

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Easy to Use

The Randomizer is accessible anytime, anywhere and via any device that has a modern web browser and is connected to the Internet. Investigators randomize subjects with only a few clicks and are immediately notified of the treatment allocation. Trial coordinators can set up a new trial in minutes. They can add trial sites and users at any time during participant enrollment.


Permuted blocks, minimization, biased coin, urn randomization, and other algorithms are available. Full support for open and double-blinded trials, a customizable role-based access control, email notifications and reporting functions are built in. For statisticians, the Randomizer provides a simulation tool which can be used to test a trial design or to generate randomization lists.

Secure & Validated

All transactions are logged, the trial's audit trail and the list of randomizations can be downloaded and analyzed at any time by authorized users. Network traffic between the web browser and the Randomizer is encrypted using TLS (Transport Layer Security) with strong encryption. The software's GCP-compliance has been confirmed by the Austrian Federal Office for Safety in Health Care (BASG).



The demo is a fully functional copy of the randomization software, except that randomization for clinical trials is limited to 10 subjects per trial. Randomization lists can be generated for up to 5000 subjects.

To access the demo, a one-time registration is required.

Visit the Demo


Our pricing is based on the type of sponsor and the number of randomizations.

Randomization Lists

  • Randomization lists up to 5000 randomizations can be generated for free using our demo

Trials with Academic Sponsors

€ 500.- per trial
(includes the first 50 randomizations)
  • € 5.- per randomization beyond the 50 randomizations limit
  • Unlimited number of trial sites
  • Unlimited trial duration

Trials with Commercial Sponsors

€ 1000.- per trial
(includes the first 70 randomizations)
  • € 10.- per randomization beyond the 70 randomizations limit
  • Unlimited number of trial sites
  • Unlimited trial duration

Special price scales for large trials (i.e. > 1000 randomizations) are available. Please contact us for a quote.

We provide registered users with access to our self-serve randomization service, subject to our Terms and Conditions. We will offer reasonable levels of continuing technical support to assist authorized users in the use of the service. Technical support is provided via email during normal business hours.

Additional services, particularly for statistical consultation, must be stipulated separately.

Our randomization service has been used successfully in hundreds of trials. However, early trial termination may occur in clinical trials due to many issues, e.g., problems with subject recruitment, etc. Therefore, if - within six months after trial activation - no more than 10 subjects have been randomized into a trial and the trial coordinator confirms trial termination, the full basic fee will be refunded.


Get Started

If you have checked out our demo and now want to get started using the Randomizer for your trial, just follow these steps:

  1. If this is the first time you are using the Randomizer for a trial, please contact us. We will respond with the link to our production server and further instructions. Once you've registered on our production system, you can start setting up your trial immediately and randomize up to 10 subjects. The limit of 10 subjects will be removed after we have received your trial registration form (see below).
  2. Download the Trial Registration Form (also available in German) and our Terms and Conditions (also available in German). Return the registration form - properly filled in and signed - as a scanned PDF via email to office@randomizer.at or contact us to get a link where you can securely upload the PDF. Please note that both the Trial Registration Form and the Terms and Conditions are in PDF format. You may need Adobe's free Adobe Reader to view these files.
  3. As soon as we have received the Trial Registration Form, we will remove the initial randomization limit from your trial.
  4. We will send you the first invoice after subject recruitment has been activated.

Publications of some of the trials that used the Randomizer

  • BendaEAM versus BEAM as conditioning regimen for ASCT in patients with relapsed lymphoma (BEB): a multicentre, randomised, phase 2 trial. eClinicalMedicine, 2023. DOI: 10.1016/j.eclinm.2023.102318.
  • Effectiveness of Lumbar Cerebrospinal Fluid Drain Among Patients With Aneurysmal Subarachnoid Hemorrhage: A Randomized Clinical Trial. JAMA Neurology, 2023. DOI: 10.1001/jamaneurol.2023.1792.
  • Hemicraniectomy in older patients with extensive middle-cerebral-artery stroke. New England Journal of Medicine, 2014. DOI: 10.1056/NEJMoa1311367.
  • Effect of high-dose vitamin D3 on hospital length of stay in critically ill patients with vitamin D deficiency: the VITdAL-ICU randomized clinical trial. JAMA, 2014. DOI: 10.1001/jama.2014.13204.
  • Partial pancreatoduodenectomy versus duodenum-preserving pancreatic head resection in chronic pancreatitis: the multicentre, randomised, controlled, double-blind ChroPac trial. The Lancet, 2017. DOI: 10.1016/S0140-6736(17)31960-8.
  • Preoperative immunonutrition in patients at nutritional risk: results of a double-blinded randomized clinical trial. European Journal of Clinical Nutrition, 2012. DOI: 10.1038/ejcn.2012.53.
  • Brief motivational intervention with homeless adolescents: evaluating effects on substance use and service utilization. Psychology of Addictive Behaviors, 2007. PMID: 18072842.
  • Optimizing Cardiac Out-Put to Increase Cerebral Penumbral Perfusion in Large Middle Cerebral Artery Ischemic Lesion - OPTIMAL Study. Frontiers in Neurology, 2017. DOI: 10.3389/fneur.2017.00402.
  • Outcomes of Hypothermia in Addition to Decompressive Hemicraniectomy in Treatment of Malignant Middle Cerebral Artery Stroke. A Randomized Clinical Trial. JAMA Neurology, 2019. DOI: 10.1001/jamaneurol.2018.4822.
  • Hemodynamic stability during induction of anesthesia in elderly patients: propofol+ ketamine versus propofol+ etomidate. Journal of Cardiovascular and Thoracic Research, 2013. PMID: 24251011.
  • Randomized clinical trial on epidural versus patient-controlled analgesia for laparoscopic colorectal surgery within an enhanced recovery pathway. Annals of Surgery, 2015. PMID: 25119117.
  • EARLYDRAIN-outcome after early lumbar CSF-drainage in aneurysmal subarachnoid hemorrhage: study protocol for a randomized controlled trial. Trials, 2011. DOI: 10.1186/1745-6215-12-203.
  • Cosmesis and body image after single-port laparoscopic or conventional laparoscopic cholecystectomy: a multicenter double blinded randomised controlled trial (SPOCC-trial). BMC Surgery, 2011. PMID: 21910897.
  • Protocol for German trial of Acyclovir and Corticosteroids in Herpes-simplex-virus-Encephalitis (GACHE): a multicenter, multinational, randomized, double-blind, placebo-controlled German, Austrian and Dutch trial [ISRCTN45122933]. BMC Neurology, 2008. DOI: 10.1186/1471-2377-8-40.
  • Pylorus resection or pylorus preservation in partial pancreatico-duodenectomy (PROPP study): study protocol for a randomized controlled trial. Trials, 2013. DOI: 10.1186/1745-6215-14-44.
  • Pancreatogastrostomy versus pancreatojejunostomy for RECOnstruction after PANCreatoduodenectomy (RECOPANC, DRKS 00000767): perioperative and long-term results of a multicenter randomized controlled trial. Annals of Surgery, 2016. PMID: 26135690.
  • Anticoagulant treatment in German family practices–screening results from a cluster randomized controlled trial. BMC Family Practice, 2014. DOI: 10.1186/s12875-014-0170-0.
  • HAnd Suture Versus STApling for Closure of Loop Ileostomy (HASTA Trial): results of a multicenter randomized trial (DRKS00000040). Annals of Surgery, 2012. PMID: 23095628.
  • Phase II trial of intravenous low-dose granulocyte colony-stimulating factor in acute ischemic stroke. Journal of Stroke and Cerebrovascular Diseases, 2016. PMID: 27017282.
  • A fast-track program reduces complications and length of hospital stay after open colonic surgery. Gastroenterology, 2009. DOI 10.1053/j.gastro.2008.10.030.
  • Differential effects of fluvastatin alone or in combination with ezetimibe on lipoprotein subfractions in patients at high risk of coronary events. European Journal of Clinical Investigation, 2010. DOI: 10.1111/j.1365-2362.2009.02249.x.
  • Immediate Occlusal versus Non‐Occlusal Loading of Implants: A Randomized Clinical Pilot Study. Clinical Implant Dentistry and Related Research, 2015. DOI: 10.1111/cid.12157.
  • Onset and duration of effect of incobotulinumtoxinA, onabotulinumtoxinA, and abobotulinumtoxinA in the treatment of glabellar frown lines: a randomized, double-blind study. Clinical, Cosmetic and Investigational Dermatology, 2013. PMCID: PMC3789632
  • Primary care management for optimized antithrombotic treatment [PICANT]: study protocol for a cluster-randomized controlled trial. Implementation Science, 2012. DOI: 10.1186/1748-5908-7-79.
  • Prevention of abdominal wound infection (PROUD trial, DRKS00000390): study protocol for a randomized controlled trial. Trials, 2011. DOI: 10.1186/1745-6215-12-245.
  • Diabetic neuropathy increases stimulation threshold during popliteal sciatic nerve block. British Journal of Anaesthesia, 2016. DOI: 10.1093/bja/aew027.
  • Amino-acid PET versus MRI guided re-irradiation in patients with recurrent glioblastoma multiforme (GLIAA)–protocol of a randomized phase II trial (NOA 10/ARO 2013-1). BMC Cancer, 2016. DOI: 10.1186/s12885-016-2806-z.
  • Randomised trial of proton vs. carbon ion radiation therapy in patients with low and intermediate grade chondrosarcoma of the skull base, clinical phase III study. BMC Cancer, 2010. DOI: 10.1186/1471-2407-10-606.
  • Early versus late pulmonary rehabilitation in chronic obstructive pulmonary disease patients with acute exacerbations: a randomized trial. Respiration, 2012. DOI: 10.1159/000329884.
  • The link between obesity and vitamin D in bariatric patients with omega-loop gastric bypass surgery-a vitamin D supplementation trial to compare the efficacy of postoperative cholecalciferol loading (LOAD): study protocol for a randomized controlled trial. Trials, 2015. DOI: 10.1186/s13063-015-0877-9.
  • Open reduction and internal fixation versus casting for highly comminuted and intra-articular fractures of the distal radius (ORCHID): protocol for a randomized clinical multi-center trial. Trials, 2011. DOI: 10.1186/1745-6215-12-84.
  • DESTINY II: DEcompressive Surgery for the Treatment of malignant INfarction of the middle cerebral arterY II. International Journal of Stroke, 2011. DOI: 10.1111/j.1747-4949.2010.00544.x.
  • Protection of pharmacological postconditioning in liver surgery: results of a prospective randomized controlled trial. Annals of Surgery, 2012. DOI: 10.1097/SLA.0b013e318272df7c.
  • Repetitive Peripheral Magnetic Stimulation (rpMS) in Combination with Muscle Stretch Decreased the Wrist and Finger Flexor Muscle Spasticity in Chronic Patients after CNS Lesion. International Journal of Physical Medicine and Rehabilitation, 2016. DOI: 10.4172/2329-9096.1000352.
  • Multicenter, randomized, controlled trial of confocal laser endomicroscopy assessment of residual metaplasia after mucosal ablation or resection of GI neoplasia in Barrett's esophagus. Gastrointestinal Endoscopy, 2012. DOI: 10.1016/j.gie.2012.05.004.
  • Interpersonal Psychotherapy vs. Treatment as Usual for Major Depression Related to Work Stress: A Pilot Randomized Controlled Study. Frontiers in Psychiatry, 2020. DOI: 10.3389/fpsyt.2020.00193.

Contact Us

If you have any questions regarding our randomization service or just have a comment for us, we'd be pleased to hear from you. Send us an email (in English or German) to office@randomizer.at (for general inquiries) or support@randomizer.at (for technical support questions) or enter your message in the form below and click "Send Message" when you are done.

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