Reversible severe myopathy during treatment with finasteride

Toxic myopathies

PURPOSE OF REVIEW

Our aim is to highlight major advances reported in the last few years in drug-induced muscle toxicity.

RECENT FINDINGS

Our focus is on myopathies induced by statins and immune checkpoint inhibitors with a brief overview of rare steroid myopathies. Statin muscle injury is frequently because of direct toxicity rather than an autoimmune mechanism. Laboratory testing and muscle pathologic features distinguish these two conditions. Statin-associated necrotizing autoimmune myopathy (SANAM) is associated with an autoantibody in 66% of cases targeting the HMGCR enzyme. The later autoantibody is a marker for necrotizing autoimmune myopathy, regardless of statin exposure. In SANAM, MHC-I antigens are expressed on the surface of intact muscle fibers. Genetic HLA loci predispose patients exposed to statins to immunologic toxicity. SANAM requires long-term therapy with multiple immunosuppressive therapies. Immune checkpoint inhibitors are powerful emerging therapies for advanced cancer that pause a novel therapeutic challenge.

SUMMARY

This review is focused on statins, the most prevalent myotoxic drug class. In addition, we examine the accumulating body of evidence of muscle injury and its management with immune checkpoint inhibitors. We anticipate the reader to become more knowledgeable in recent discoveries related to these myotoxic drugs, and their mechanisms of action and management.

Risk of rhabdomyolysis from 5-α reductase inhibitors

PURPOSE

A recent regulatory warning and case reports have described the development of muscle complications with the use of 5-α reductase inhibitors (5ARIs). We wished to determine if there was a link between rhabdomyolysis and 5ARI usage.

METHODS

We used a matched cohort design and linked administrative data from the province of Ontario, Canada, to investigate the risk of rhabdomyolysis in men using either finasteride or dutasteride. A total of 99 covariates were measured. We identified 93 197 men ≥66 years of age who initiated a new prescription for a 5ARI, and they were matched using a propensity score to an equal number of men not prescribed a 5ARI.

RESULTS

New initiation of 5ARIs was not associated with a significantly increased risk of rhabdomyolysis (hazard ratio [HR] 1.21, 95% confidence interval [CI], 1.00-1.48, P = .06). When we examined the risk of rhabdomyolysis in the year prior to the initiation of a 5ARI, we found that men who would go on to use a 5ARI in the future had an elevated risk of rhabdomyolysis even prior to starting the medication (HR 1.31, 95% CI, 1.05-1.64, P = .01). Our secondary outcome of myositis and myopathy was significantly higher among 5ARI users (HR 1.63, 95% CI, 1.48-1.80, P < .01), and this risk was not present prior to 5ARI usage.

CONCLUSION

5-α reductase inhibitors do not appear to be associated with the development of rhabdomyolysis; however, they may be associated with an increased risk of myopathy and myositis.

A population-based nested case-control study: the use of 5-alpha-reductase inhibitors and the increased risk of osteoporosis diagnosis in patients with benign prostate hyperplasia

BACKGROUND

5-alpha-reductase inhibitors (5ARIs) are the potent androgen responsible for the development and enlargement of the prostate gland by decreasing dihydrotestosterone (DHT). This results in inhibition of the conversion of testosterone to dihydrotestosterone and markedly suppresses serum dihydrotestosterone levels. Testosterone replacement therapy improves bone density in men with hypogonadal osteoporosis. This study explores the possible association between the use of two typical 5ARIs (finasteride and dutasteride) and the subsequent risk of osteoporosis diagnosis.

METHODS

We identified 1352 osteoporosis diagnosis cases and 5387 control cases without osteoporosis diagnosis from the claims data for patients with benign prostate hyperplasia (BPH), which are collected in the Taiwanese National Health Insurance Research Database (NHIRD). Four controls were frequency matched to each case according to age (every 5 years) and diagnosis date. We measured the effect of 5ARIs and determined the adjusted odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

We observed a 1·52-fold increase in osteoporosis diagnosis among patients with BPH using finasteride (95% CI, 1·01-2·30). Furthermore, a dosage analysis showed that higher doses of finasteride were associated with higher osteoporosis diagnosis risk (OR = 1·68; 95% CI, 1·01-2·81), relative to the patients not using 5ARIs.

CONCLUSION

This population-based nested case-control study suggests that the use of finasteride can increase the risk of osteoporosis diagnosis among patients with BPH. The effects were more prominent in patients using higher doses of finasteride.

Toxic myopathies

Muscle tissue is highly sensitive to many substances. Early recognition of toxic myopathies is important, because they potentially are reversible on removal of the offending drug or toxin, with greater likelihood of complete resolution the sooner this is achieved. Clinical features range from mild muscle pain and cramps to severe weakness with rhabdomyolysis, renal failure, and even death. The pathogenic bases can be multifactorial. This article reviews some of the common toxic myopathies and their clinical presentation, histopathologic features, and possible underlying cellular mechanisms.

Fraction of macroporous resin from Smilax china L. inhibits testosterone propionate-induced prostatic hyperplasia in castrated rats

The present study was conducted to evaluate the effect of a fraction of macroporous resin (FMR), a bioactive component of Smilax china L., on benign prostatic hyperplasia (BPH) in castrated rats induced by testosterone propionate. Rats were randomly divided into five groups: the negative control group (sham-operated), the model group, two FMR-treated groups (at doses of 300 mg/kg and 600 mg/kg of body weight), and the positive control group (treated with finasteride at the dose of 3 mg/kg). Drugs were administered once a day for three consecutive weeks by gastric gavage. Prostates were weighed, testosterone and dihydrotestosterone (DHT) levels in serum were determined, and histopathological examinations were carried out. FMR treatment inhibited prostatic hyperplasia, reducing the DHT level in serum and improving the prostate gland morphology compared with the model group. The overall results of this study suggest that FMR is effective at inhibiting experimentally induced prostate enlargement, and it presents a valuable resource for the treatment of human BPH.

Finasteride-induced myalgia and HyperCKemia

BACKGROUND

Finasteride is an antiandrogen, inhibits type II 5-alpha reductase (enzyme that converts testosterone to more potent form dihydrotestosterone), and is commonly used in the treatment of benign prostatic hyperplasia and male frontal baldness; however, it is not free from side effects, which include sexual dysfunction and, rarely, myopathy. We report a case of finasteride-associated myalgia and hyperCKemia and review similar cases reported in the literature.

CASE REPORT

A 30-year-old man who had been taking finasteride 5 mg/d for 10 years to treat frontal baldness developed diffuse muscle aches associated with elevated creatine kinase level to 10,117 IU/L with neither weakness nor pigmenturia. His symptoms resolved and his creatine kinase level dropped down to 256 IU/L 3 weeks after finasteride discontinuation.

CONCLUSION

Reversible myalgia associated with significant hyperCKemia is a possible adverse reaction of finasteride therapy.

Finasteride in the treatment of alopecia

Finasteride is a 5alpha-reductase inhibitor approved for the treatment of male pattern hair loss. Originally approved for the treatment of benign prostatic hypertrophy in 1992, its approval was expanded in 1997 to include the treatment of androgenetic alopecia (AGA) in men at a dose of 1 mg/day. Finasteride inhibits 5alpha-reductase, thereby prohibiting the conversion of testosterone to dihydrotestosterone (DHT), which is implicated in the development of hairless in some men. Reduction in DHT results in a significant improvement in subjective and objective assessments of hair growth and density. Finasteride is well-tolerated with a favourable adverse event history. The most common adverse events include reduced libido, decreased ejaculate volume and gynaecomastia.

The mechanism of epristeride against benign prostatic hyperplasia

Epristeride, a 5alpha-reductase inhibitor, decreases prostate size and improves symptoms in men with benign prostatic hyperplasia. However, little is known about the histopathology of the prostate after treatment with epristeride. To study the relationship between apoptosis and the mechanism of epristeride in the treatment of benign prostatic hyperplasia, the induction of apoptosis by epristeride was detected and measured in vitro by: (a) observing morphological changes in cells by light microscopy; (b) comparing the relative content of dihydrotestosterone in the rat prostate epithelial cells untreated and treated with epristeride by microspectrophotometry; (c) estimating changes in cell size and DNA integrity by flow cytometry; and (d) monitoring nucleosomal DNA fragmentation by agarose gel electrophoresis. The cells treated with epristeride showed a reduction in cell size, an increase in the cytoplasm/nuclear ratio, which is indicative of the condensation of nuclear chromatin, a significant decrease in optical density at 580 nm (OD580 nm), and an oligonucleosomal ladder and a subdiploid peak of DNA characteristic of apoptosis. Therefore, the mechanism of epristeride in the treatment of benign prostatic hyperplasia might be apoptosis stimulated by decreasing dihydrotestosterone level.

Reversible long-term toxicity of epristeride in beagle dogs

Epristeride (17beta-N-t-butylcarboxamide-androst-3, 5-diene-3-carboxylic acid) is an uncompetitive inhibitor of steroid 5alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT), and has been shown to retard the growth of hyperplastic prostates. The objective of the current investigation was to research the toxic effects of epristeride and to demonstrate its reversible. In the experiment, 18 beagle dogs (male, about 6 months old) were used and divided into six groups, with each group containing three dogs. Groups A and B were placebo-treated for 180 and 240 days, Groups C and D were treated with 10 and 100 mg/kg epristeride for 180 days, and Groups E and F were treated with 10 and 100 mg/kg epristeride for 180 days and then were placebo-treated for 60 days (total 240 days), respectively. Routine analyses were performed at the 1st, 30th, 90th, 180th, and 240th days, and the dogs were autopsied at the 180th or 240th day for systemic examination and measured for relative DNA content in single prostatic epithelial cells. Each prostate was fixed with 4% Formalin, embedded in paraffin, sectioned at 6 micron, and immunohistochemically stained for assaying the relative content (transmittance) of prostatic specific antigen (PSA) and DHT (%) with a microspectrophotometer at 650-nm wavelength. The results were that 180 days of toxicity with epristeride (100 mg/kg) on interstitial cells of testes and DNA in prostatic epithelial cells couldn't reverse during 60 days of convalescence and that the DHT and PSA levels in the gland, the volume of the gland, glandular epithelial cell height, and acinar luminal area could reverse to normal during the same convalescence. To our knowledge this is the first study documenting the toxicity of epristeride. It is necessary to further study the molecular and clinical toxicity of epristeride.