Painful gynecomastia: an unusual toxicity of gabapentin?

Gynecomastia and drugs: a critical evaluation of the literature

PURPOSE

A large number of medications have been implicated in the genesis of gynecomastia. However, gynecomastia is common in men, asymptomatic, increases with age, and is considered to be due to an increased estradiol/testosterone ratio. This complicates the interpretation of medication-related gynecomastia. Therefore, we have reviewed the literature in order to assess the data relating gynecomastia onset with utilization of specific medications.

METHODS

The literature was searched in PubMed and the Ovid/Medline databases from the 1946 to January 2015 with the search terminology of "gynecomastia, drugs/medications." A few other articles were found and included.

RESULTS

One hundred ten publications were reviewed. Sixty-three were single case reports. There were 24 population-based studies of which 8 were HIV-infected patients treated with antiretroviral agents. Among the case reports, 49 were for individual medications, and 2 were reports of antineoplastic or antiretroviral drug regimens. In the great majority, mastodynia with or without breast enlargement was present and referred to as gynecomastia. Generally, hormonal profiles could not explain the breast enlargement. The pain/tenderness and breast enlargement resolved spontaneously over time.

CONCLUSION

Many different medications have been associated with the presence of "gynecomastia." Generally, it presents as a syndrome characterized by a single painful/tender breast (mastodynia) associated with breast enlargement and is transient. We suggest that these cases be referred to as an acute gynecomastia syndrome. This syndrome also occurs independent of medication use. Thus, in an individual patient, whether it is medication induced often remains uncertain. The pathogenesis remains unknown.

Drug-induced gynecomastia

Drugs account for about 20% of gynecomastia cases in men. As a number of factors can alter the estrogen:androgen ratio, several pathophysiologic mechanisms are associated with drugs causing this disorder. Antiandrogens, protease inhibitors, and nucleoside reverse transcriptase inhibitors are the most common drug causes of gynecomastia, whereas first-generation antipsychotics, spironolactone, verapamil, and cimetidine are less common causes. Other drugs have been reported rarely as causes. Treatment may involve switching to an alternative agent or may require surgery or irradiation if the causative agent cannot be discontinued. We reviewed the literature on drug-induced gynecomastia and provided another perspective by reviewing data from the United States Food and Drug Administration's Adverse Event Reporting System. Epidemiologic studies are needed to provide a more accurate description of the frequency of drug-induced gynecomastia.

Gabapentin and pregabalin for chronic neuropathic and early postsurgical pain: current evidence and future directions

PURPOSE OF REVIEW

Gabapentin and pregabalin bind to the alpha-2-delta calcium channel subunit and represent a novel analgesic drug class. The evidence base supporting their use for chronic neuropathic and early postsurgical pain is reviewed.

RECENT FINDINGS

Multiple, large, high-quality trials have demonstrated the safety and efficacy of gabapentin and pregabalin in neuropathic pain. Treatment-related improvement of pain and sleep positively impact upon quality of life. Sedation, dizziness and ataxia are important and relatively common adverse effects, however. Accumulating evidence indicates that gabapentin, and possibly pregabalin, also exert important effects following surgery. Multiple high-quality trials have demonstrated analgesic and opioid-sparing efficacy with gabapentin following various surgical procedures. Gabapentin and pregabalin reduce movement-evoked pain and this can lead to enhanced functional postoperative recovery. Postoperative opioid sparing is of questionable relevance since few trials have shown reduced opioid-related adverse effects. Sedation, dizziness and ataxia have been reported in only a few trials. Future larger-scale perioperative trials focused on safety assessment are needed, however.

SUMMARY

Gabapentin and pregabalin are efficacious treatments for neuropathic and postsurgical pain. Future research addressing several specific questions would serve to better delineate their optimal roles in treating these and other pain conditions.

Golf-inhibiting gynecomastia associated with atorvastatin therapy

Gynecomastia can have a significant emotional and social impact on men. Although numerous drug therapies may cause this condition, we found no documented cases of gynecomastia associated with atorvastatin. We describe the development of breast enlargement and tenderness in a 52-year-old Caucasian man 6 months after his simvastatin therapy had been switched to atorvastatin. His symptoms ultimately interfered with his ability to play golf and participate in other activities. These problems resolved after atorvastatin discontinuation and did not recur despite resumption of simvastatin therapy. The gynecomastia in this patient represented a possible adverse effect of atorvastatin according to the Naranjo adverse drug reaction probability scale. The mechanism may be atorvastatin's theoretical suppression of adrenal or gonadal steroid production through effects on cholesterol synthesis. Based on this and other case reports, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) should be considered as a potential cause when evaluating otherwise unexplainable cases of gynecomastia in patients taking these drugs.

Two cases of painful gynecomastia and lower extremity pain in association with pregabalin therapy

We report two patients with refractory epilepsy who developed unilateral painful gynecomastia and lower extremity pain (one of them localized and the other one diffuse), shortly after receiving Pregabalin (PGB). Neither of them had previous endocrinologic problems or complaints about pain on their medical history. PGB was stopped in one patient and reduced in the other one, with complete disparition of the symptoms in the following weeks in both patients. This supports the hypothesis that gynecomastia could be a drug-induced and easy to manage secondary effect of PGB, with a higher incidence than observed on previous clinical trials.

Gabapentin-Induced Neurologic Toxicities

Gabapentin is an antiepileptic drug approved for the treatment of postherpetic neuralgia and as adjunctive therapy for partial seizures. The drug has been shown to be safe and nontoxic. The current literature has limited reports of neurologic toxicity associated with gabapentin therapy in patients with or without renal dysfunction. We describe the case of a 75-year-old man with renal dysfunction who developed neurologic toxicity due to gabapentin accumulation. Future studies are warranted to confirm the neurologic adverse effects of gabapentin, including any additional risks in patients with renal dysfunction.