Proviron

No current UK-licensed Summary of Product Characteristics for Proviron or mesterolone could be located on the UK electronic medicines compendium (emc) as of this access date, and a UK consumer medicines-information reference states Pro-Viron tablets were discontinued in the UK in September 2018. Proviron/mesterolone is not absent from the market everywhere: a current Bayer Proviron SmPC (authorisation last renewed May 2023) remains in active use in at least the United Arab Emirates, Oman and Kuwait, and an EMA list of nationally authorised mesterolone products dated October 2025 shows Proviron products still authorised in Spain, Greece and Portugal. Presenting Proviron/mesterolone as a currently UK-licensed medicine, or describing its 2008 UK label as a current authoritative label, would be inaccurate.^[6][7][3][8]

Jurisdiction

European Union (Spain, Greece, Portugal per EMA's October 2025 list)

Product

Proviron (mesterolone) 25 mg tablets

Indication

Currently nationally authorised in the listed EU member states, and separately marketed under a currently renewed Bayer label in the United Arab Emirates, Oman and Kuwait; no current UK-licensed SmPC was found on the UK emc as of this access date, and the commonly cited September 2018 UK discontinuation rests on a secondary consumer reference, not a primary MHRA determination

Record date

2026-09-08

• No official MHRA discontinuation record was located or inspected; the September 2018 date rests on a secondary consumer-health reference, not a primary regulator record, and remains an externally unresolved point for a future worker with MHRA-specific access.
• An empty emc search result is a strong but not absolute indicator; emc is a near-comprehensive registry of UK-licensed medicines, not a legally exhaustive one.
• This claim describes market/authorisation status only; it makes no statement about the safety, efficacy or endocrine effects of mesterolone.

A study of male weightlifters associated long-term mixed AAS exposure with lower left-ventricular function and greater coronary plaque volume than in non-users. The observational design cannot isolate an individual steroid or prove a precise risk of heart attack.^[4]

• Class-context evidence from selected male weightlifters; residual confounding and uncertain historical exposures remain.
• This finding and the interaction file's "safety-aas-cardiovascular" note rest on the same single study, held under two source records. Seeing both is not two studies agreeing.

The HAARLEM echocardiography cohort found increased left-ventricular mass and reduced function during mixed AAS use. Left-ventricular mass and the E/A ratio returned to baseline at follow-up, when only 25 of 31 participants had recovery imaging. These group findings cannot promise that every person or repeated exposure recovers.^[5]

• Small cohort, coexposures and missing follow-up; no clinical-event or molecule-specific risk estimate.

A cross-sectional study of male weightlifters associated long-term illicit AAS use with impaired cardiac function and more coronary plaque. The study cannot establish the risk from one particular compound, dose or combination.^[4]

• This note and the compound records' "general-anadrol-safety-86" finding rest on the same single study, held under two source records. Seeing both is not two studies agreeing.
• Observational evidence, self-reported mixed exposures and potential confounding; not a comparison of medically indicated testosterone treatment.
• This is the same underlying study cited at full-text scope elsewhere in the site (content/evidence/general.ts "general-aas-cardiovascular-full"); it is one single source, not independent corroboration.

FDA reports serious liver injury and other serious reactions involving steroid or steroid-like bodybuilding products. It advises immediately consulting a healthcare professional, including before abrupt cessation, because of dangerous withdrawal problems that can arise from quickly stopping such products.^[9]

• General product safety communication, not an incidence estimate for every listed steroid.

In the HAARLEM cohort of men using mixed anabolic-androgenic steroids, testosterone and sperm recovery differed. The final visit was one year after cycle start, not one year after cessation, and some abnormal final results were already present at baseline. The study did not measure pregnancy or live birth and does not provide a universal recovery deadline.^[1]

• Class-context evidence: mixed exposures cannot isolate any individual molecule or ester, and follow-up was too short to characterize all recovery.
• Final hormone and semen denominators differ; attrition and resumed use limit recovery inference.

A historical Pro-Viron SmPC formatted for the UK market (text revised May 2008) reported an oral mesterolone terminal half-life of 12-13 hours. The identical 12-13 hour terminal half-life figure appears in a current Bayer Proviron SmPC used in other markets (last renewed May 2023; text revised November 2023), giving independent-document corroboration of the same manufacturer-reported value. Historical therapeutic observations in either label do not establish absent endocrine suppression or a protective effect in an AAS combination.^[2][3]

• Historical formulation-specific label; current UK regulatory status has not been established by this record (see the separate general-proviron-regulatory-2026 claim).
• The 2008 UK-formatted label could not be freshly reopened on this access date (publisher access blocked); its prior inspection record is preserved as historical input rather than upgraded.
• The corroborating 2023 label is formatted for Gulf-region markets (UAE, Oman, Kuwait pharmacovigilance contacts), not the UK. Matching values across two manufacturer labels is not independent primary pharmacokinetic research; both derive from the same underlying data package.

Long-term illicit AAS exposure was associated with myocardial dysfunction and greater coronary plaque in male weightlifters. Concern about combining AAS follows from this class evidence; the incremental risk of any two steroids was not measured, and the paper does not name or compare specific steroid combinations.^[4]

• Observational, mixed self-reported exposure; no pair-specific causal estimate.
• This is the same underlying study cited at full-text scope elsewhere in the site (general.ts "general-aas-cardiovascular-full"); it is one single source, not independent corroboration.

FDA warns that people who “stack” steroid-like bodybuilding products with other products, including stimulants, may be at greater risk for serious and life-threatening reactions. This broad warning does not establish the effect or severity of an individual compound pair.^[9]

• This evidence does not establish the magnitude or frequency of harm from the selected combination.

A review of testosterone-treatment studies found increased hemoglobin and hematocrit. Extrapolating to combined anabolic steroids suggests a possible overlapping effect, but the review did not establish pair-specific thrombosis risk.^[10]

• This evidence does not establish the magnitude or frequency of harm from the selected combination.

Testosterone-related hematocrit increases and tamoxifen/raloxifene thromboembolic findings come from different study populations. They motivate a possible overlapping concern, not evidence of a measured thrombosis increase from the selected pair.^[10][11]

• This evidence does not establish the magnitude or frequency of harm from the selected combination.

A controlled study in men given goserelin, testosterone gel and anastrozole linked estrogen deficiency to increased body fat and a contribution to reduced sexual function. Only anastrozole was studied; it does not establish the outcome of combining aromatase inhibitors generally, or of adding anastrozole specifically to a particular anabolic steroid.^[12]

• This evidence does not establish the magnitude or frequency of harm from the selected combination.
• Exemestane and letrozole were not administered in this trial and do not inherit this observation; the compound scope and the corresponding rule's applicable IDs are narrowed to anastrozole (see interactionsFileNotes).