Study of lidocaine hydrochloride, ropivacaine, and sodium chloride on acute pain in healthy adults aged 18‑64

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What is this study about?

The study examines Acute pain and tests whether the systemic pain‑relieving effect of two local anesthetics, lidocaine hydrochloride and ropivacaine, given as a Transversus Abdominis Plane (TAP) block, is better than a placebo. The purpose of the study is to prove superior systemic analgesic effect of the two anesthetics after the block using an experimental pain model. A TAP block is an injection placed near the nerves of the abdominal wall to numb the area.

Healthy volunteers will receive each of the three injections (the two anesthetics and the placebo) in separate study periods, with the order chosen at random and neither the participants nor the staff knowing which injection is given at any time. After each injection, a small device will apply electrical stimulation to create a temporary area of increased pain sensitivity called hyperalgesia, and participants will rate the pain they feel. Additional tests will use a cuff that inflates around the arm to measure the pressure at which pain is first felt and the pressure that can be tolerated, known as cuff-pressure algometry. Throughout the study, blood pressure, heart rate, any side effects and adverse events will be recorded, and each participation period lasts only a few days.

1 randomization and study sequence assignment

after you agree to join, a computer program randomly determines the order in which you will receive the six study interventions. the order is kept unknown to you and the staff.

the six interventions include ropivacaine, lidocaine, and a placebo (sodium chloride). each will be given once during the study.

2 baseline assessments

before any medication is given, measurements are taken to record your normal pain sensitivity and vital signs.

these include the area of pinprick hyperalgesia, pain intensity from electrical stimulation, cuff‑pressure pain tolerance, blood pressure, and heart rate.

3 first tap block procedure

a transversus abdominis plane (tap) block is performed using the medication assigned for this period.

if the assigned medication is ropivacaine, a dose of 225 (unit not specified) is injected around the nerves.

if the assigned medication is lidocaine, a dose of 400 (unit not specified) is injected.

if the assigned medication is the placebo, sodium chloride is injected at 0.4 millilitre per kilogram of body weight.

4 post‑administration monitoring and pain testing

after the injection, you are observed for a short period while the medication takes effect.

the same pain tests performed at baseline are repeated to evaluate changes in hyperalgesia, pain intensity, and cuff‑pressure thresholds.

blood pressure, heart rate, and any side effects are also recorded.

5 washout period

a washout interval is observed to allow the previous medication to leave your system before the next intervention.

no study medication is given during this time, but routine safety checks continue.

6 repeat for each remaining study arm

steps 2 through 5 are repeated for each of the remaining five interventions, following the order determined by randomization.

each arm uses the same dosage and administration method described in step 3.

the same set of measurements is collected after each injection to compare the systemic effects of ropivacaine, lidocaine, and the placebo.

7 final study completion

after the last arm is finished, a final set of assessments is performed.

all data are compiled for analysis, and you are thanked for your participation.

Who Can Join the Study?

Age must be between 18 and 64 years at the time you sign the study paperwork.
You need to be generally healthy, as judged by a medical check, and have an ASA physical status classification of 1 or 2 (a rating that shows you have no or only mild health problems).
Your body weight must be between 60 and 95 kilograms and your BMI (body mass index, a way to assess body size using height and weight) must be between 18 and 35 kg/m².
You must be male.
You must be able to sign a written informed consent form, which means you understand the study and agree to take part.

Who Cannot Join the Study?

Neurologic disease, nerve‑ or vascular impairment: You cannot join if you have any disorder that affects your brain, nerves, or blood vessels, such as multiple sclerosis, peripheral neuropathy, or problems with blood flow.
Known coagulopathy: This means a condition that makes your blood clotting abnormal, like hemophilia or taking medication that prevents clotting.
Allergic to local anaesthetic agents: If you have had an allergic reaction to medicines that numb a specific area (for example, lidocaine or ropivacaine), you are not eligible.
Skin infection or exanthema at the site for TAP block or the sites involved in sensory testing: You cannot participate if there is an infection (like a boil or cellulitis) or a rash (exanthema) on the skin where the TAP block would be performed or where the pain tests would be done.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Oslo Universitetssykehus HF	Oslo	Norway

Other Sites

No sites found in this category

Trial status

Country	Status	Recruitment Start
Norway	Not yet recruiting	01.07.2026

Trial locations

Investigated drugs:

Ropivacaine is a local anesthetic that is injected near a nerve (perineural use) to numb the area where a Transversus Abdominis Plane (TAP) block is performed. In this study participants receive ropivacaine during the TAP block, and researchers watch how the medicine may travel into the bloodstream and reduce overall pain sensitivity and the feeling of heightened pain (hyperalgesia). The goal is to see if ropivacaine can provide a stronger systemic pain‑relieving effect compared with not receiving an active drug.

Lidocaine is another local anesthetic used in the same way—placed around the nerves during a TAP block. The trial gives lidocaine to participants to examine whether it can enter the blood and lessen general pain perception and the area of increased sensitivity after the block. By comparing lidocaine’s effects with those of ropivacaine, the study aims to determine which drug offers a better overall pain‑relieving benefit when used for this type of nerve block.

Acute pain – Acute pain is a sudden, sharp sensation that arises directly from tissue injury or inflammation. It typically begins immediately after the harmful event and reaches its highest intensity within minutes. The sensation may spread to nearby areas and can be heightened by movement or pressure. If the underlying cause heals quickly, the pain usually diminishes within a short time. When the source persists, the pain may linger and become less intense but more widespread.

Trial ID:

2025-520910-67-01

Protocol code:

LASER

Trial Phase:

Therapeutic confirmatory (Phase III)

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Study of lidocaine hydrochloride, ropivacaine, and sodium chloride on acute pain in healthy adults aged 18‑64

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?