Intrathecal Paracetamol Before Spinal Anaesthesia With Chloroprocaine HCl 1% for Short Knee Procedures

This is a phase II, single centre, randomised, parallel-group, double-blind, three doses, placebo-controlled, exploratory efficacy and safety study. The objective of this study is to investigate the efficacy and safety of a single intrathecal injection of Paracetamol 3% (30 mg/mL) administered at 3 doses to 3 active treatment groups, as compared to placebo, for post-operative analgesia in knee procedures up to 40 min duration performed under spinal anaesthesia with Chloroprocaine HCl 1%.

Eligible patients undergoing elective short-duration knee procedures up to 40 min duration will be randomised into 4 treatment groups (15 patients per group) to receive either one of the 3 single doses of Paracetamol 3% (D1: 30 mg, D2: 60 mg, D3: 90 mg) or the placebo solution (P: 0.9% saline solution) by intrathecal injection (IT), according to the randomised, parallel-group design.

Immediately after IT paracetamol or placebo administration, all patients will receive a single IT dose of Chloroprocaine HCl 1% (Non-investigational medicinal product, NIMP) according to the Summary of Product Characteristics indications. The time interval between paracetamol IT and chloroprocaine IT injections should not exceed 2 min.

The study will include a screening phase (Visit 1, Day -21/-1), a treatment phase (IMP IT administration, anaesthesia and surgical procedure: Visit 2, Day 1) and a follow-up phase including an observation period (Visit 3), a final visit and two follow-ups (24 h post-dose and day 7±1).

Eligibility Criteria:
Inclusion Criteria:

1. Informed consent: signed written informed consent before inclusion in the study
2. Sex, age and surgery: male/female patients, 18-80 years old (inclusive), scheduled for short duration (up to 40 min) knee procedures
3. Body Mass Index (BMI): 18 - 32 kg/m2 inclusive
4. ASA physical status: I-III
5. Full comprehension: ability to comprehend the full nature and purpose of the study, including possible risks and side effects; ability to co-operate with the investigator and to comply with the requirements of the entire study.

Exclusion Criteria:

1. Physical findings: clinically significant abnormal physical findings which could interfere with the objectives of the study. Contraindications to spinal anaesthesia. History of neuromuscular diseases to the lower extremities
2. ASA physical status: IV-V
3. Further anaesthesia: patients expected to require further anaesthesia
4. Allergy: ascertained or presumptive hypersensitivity to the active principles (paracetamol and/or ester type anaesthetics) and/or formulations' ingredients or related drugs, non-steroidal anti-inflammatory drugs and/or opioid derivatives; history of anaphylaxis to drugs or allergic reactions in general, which the investigator considers could affect the outcome of the study
5. Chronic pain syndromes: patients with chronic pain syndromes taking opioids, anticonvulsant agents or chronic analgesic therapy
6. Pain assessment: patients anticipated to be unable to make a reliable self-report of pain intensity
7. Diseases: significant history of renal, hepatic, gastrointestinal, cardiovascular, respiratory, skin, haematological, endocrine or neurological diseases that may interfere with the aim of the study; ascertained psychiatric and neurological diseases, sepsis, blood coagulation disorders, severe cardiopulmonary disease, thyroid disease, diabetes, other neuropathies, history or evidence of heart failure. History of severe head trauma that required hospitalisation, intracranial surgery or stroke within the previous 30 days, or any history of intracerebral arteriovenous malformation, cerebral aneurism or CNS mass lesion
8. Medications: medication known to interfere with the extent of spinal blocks for 2 weeks before the start of the study. Paracetamol formulations, other than the investigational product, for 2 weeks before the start of the study and during the study. Hormonal contraceptives for females are allowed. Anti-hypotensive, anti-bradycardia (e.g. ephedrine, atropine, Ringer's solution), anti-haemetic and anti-nausea medications will be allowed
9. Investigative drug studies: participation in the evaluation of any investigational product for 3 months before this study. The 3-month interval is calculated as the time between the first calendar day of the month that follows the last visit of the previous study and the first day of the present study
10. Drug, alcohol: history of drug or alcohol abuse according to the Investigator's opinion
11. Pregnancy and lactation: positive pregnancy test at screening (if applicable), pregnant or lactating women \[The pregnancy test will be performed to all fertile women and to all women up to 55 years old, if not in proven menopause (available laboratory test confirming menopause or surgically sterilised)\]