In this study, the investigators are testing a new formulation of lidocaine for its suitability in managing chronic scrotal pain (CSCP). The new formulation ST-CP is a lidocaine sustained-release formulation and is expected to provide pain relief over 4 weeks. Currently, the drug lidocaine is not available as an injectable slow-release formulation and chronic scrotal pain patients are often left untreated.

The purpose of this study is to find out if a new polymeric, water-free formulation of lidocaine is safe and can provide effective, long-lasting pain relief in chronic scrotal pain (CSCP) patients. This new formulation ST-CP is injected into the spermatic cord of patients in a very comparable way that the currently available lidocaine solution (Lidocaine HCl 1% USP) is administered. The only difference is that the polymer solution stays in the area of injection longer by forming a soft implant.

The investigators therefore hypothesize that the polymer formulation of lidocaine will release the drug over an extended period of time and will not dissolve away like the currently used lidocaine solution (Lidocaine HCl 1%, USP). This will lead to long-lasting pain relief for CSCP patients.

The investigators' primary objective is to determine if the single injection of our polymeric lidocaine formulation is well tolerated by patients with CSCP. Secondary objectives are to determine the duration and extent of pain relief, the impact of ST-CP on pain-related quality of life and the systemic exposure to lidocaine.

The clinical study is conducted at the Vancouver Prostate Centre. Potential participants will undergo a screening period to determine basal pain levels over 7 days and test their ability to respond to a spermatic cord block with a standard lidocaine injection (Lidocaine HCl 1%, USP). Up to 15 men will receive our ST-CP study formulation and will be monitored over the the following 4 weeks. Follow-up procedures will include blood draws, daily pain evaluations and standard questionnaires on scrotal pain and erectile function. Up to 3 dose levels are planned but dose escalation will only occur once the previous cohort (3 patients) has completed the follow up and safety assessment.

Summary descriptive statistics (including mean and standard deviation, median, range, proportion) will be provided for important parameters and outcome measures. These include subject demographics, subject disposition, subject compliance, pharmakokinetic laboratory test outcomes, overall adverse events, adverse events related to lidocaine and adverse events related to study procedure. Pain scores and questionnaires will be summarized by score and pre- and post- treatment levels will be compared.

Inclusion Criteria:

• Adult ( ≥ 19 years) male
• Unilateral scrotal pain lasting >3 months
• Average daily maximum scrotal pain score over 7 days ≥ 5 on the 0-10 NRS (see study protocol attached in 9.1.)
• Positive response to test spermatic cord block with 1% Lidocaine (Lidocaine HCl 1%, USP), defined as a temporary decrease of at least two points on the NRS (see study protocol attached in 9.1.) within an hour of injection

Exclusion Criteria:

• Negative response to test spermatic cord block, defined as absence of a temporary decrease of at least two points on the NRS (see study protocol attached in 9.1.) within an hour of injection
• Other pain generator site with NRS ≥ 5
• History of allergic reaction to lidocaine or any other component of ST-CP Lidocaine
• Known hypersensitivity to anesthetics of the amide-type.
• Complete heart block.
• Use of anticoagulants (Aspirin permitted)
• Active infection involving the urinary tract or scrotum
• Inability to give consent
• Inability to follow up according to the protocol
• Negative response to previous spermatic cord block.