Can pregabalin cause left anterior flank (loin) pain?

Pregabalin Does Not Cause Left Anterior Flank (Loin) Pain

Pregabalin is not associated with left anterior flank pain or loin pain as a recognized adverse effect. The extensive clinical trial data and systematic reviews examining pregabalin's safety profile do not identify flank pain, loin pain, or localized unilateral abdominal/back pain as adverse events associated with this medication 1, 2, 3, 4.

Established Adverse Effect Profile of Pregabalin

The well-documented adverse effects of pregabalin are predominantly neurological and systemic, not localized musculoskeletal or visceral pain:

Most Common Adverse Effects (Dose-Dependent)

• Dizziness occurs in 23-46% of patients and is the most frequent reason for treatment discontinuation 2
• Somnolence affects 15-25% of patients, leading to discontinuation in approximately 3% 2
• Peripheral edema occurs in approximately 10% of patients, particularly problematic in elderly individuals 2, 5
• Weight gain is a recognized adverse effect, especially with elevated serum creatinine levels 5

Other Neurological Effects

• Ataxia, confusion, thinking abnormalities, tremor, abnormal gait, and amnesia occur less frequently but remain clinically significant 2
• Unsteadiness is predicted by advanced age rather than dose-dependent factors, with nonsteroidal anti-inflammatory drugs showing protective effects (OR 0.132) 5

Gastrointestinal Effects

• Dry mouth and constipation are common 2
• Nausea is reported but less prominent than with duloxetine 1

Critical Clinical Reasoning

If a patient develops left anterior flank pain while taking pregabalin, investigate alternative etiologies rather than attributing it to the medication:

Differential Diagnosis to Consider

• Renal pathology: Nephrolithiasis, pyelonephritis, or renal infarction (pregabalin is 85-95% renally excreted unchanged, making renal function monitoring essential) 6, 7
• Musculoskeletal causes: Muscle strain, rib pathology, or referred pain from spine
• Gastrointestinal sources: Splenic pathology, colonic issues, or pancreatic tail involvement
• Vascular causes: Particularly in patients with peripheral edema from pregabalin

Important Monitoring Consideration

• Pregabalin requires mandatory dose reduction in renal impairment (50% reduction for creatinine clearance 30-60 mL/min, 75% for 15-30 mL/min, 85-90% for <15 mL/min) 6
• Elevated serum creatinine predicts both weight gain (OR 6.439) and edema (OR 6.912) 5
• If flank pain represents undiagnosed renal pathology, continued standard-dose pregabalin could lead to drug accumulation and increased adverse effects

Evidence Quality Assessment

The absence of flank pain as a pregabalin adverse effect is supported by:

• High-quality systematic reviews including 45 randomized controlled trials with 11,906 participants for neuropathic pain 4
• Cochrane reviews with comprehensive adverse event reporting from multiple large trials 3, 4
• American College of Physicians clinical practice guidelines based on systematic review of 12 antiseizure medication trials 1
• Specific adverse event prediction studies that identified factors for somnolence, unsteadiness, weight gain, and edema but not localized pain 5

The consistent absence of flank pain across thousands of participants in rigorous clinical trials provides high-quality evidence that this is not a pregabalin-related adverse effect.