Pro-Viron^®

Each tablet contains 25mg mesterolone.

Tablets.

Androgen deficiency or male infertility when associated with primary or secondary male hypogonadism.

The following dosages are recommended:

Adults:

Initially: 3 or 4 tablets daily for several months, followed by maintenance therapy of 2-3 tablets (50-75mg) daily.

Children:

Not recommended in children.

Pro-viron is contraindicated in the presence of prostatic carcinoma since androgens can stimulate the growth of an existing carcinoma. Previous or existing liver tumours. Hypersensitivity to the active substances or to any of the excipients.

Androgens are not suitable for enhancing muscular development in healthy individuals or for increasing physical ability. Regular examination of the prostate during treatment is advised, in order to exclude prostatic carcinoma.

In rare cases benign, and in even rarer cases, malignant liver tumours leading in isolated cases to life-threatening intra-abdominal haemorrhage have been observed after the use of hormonal substances such as the one contained in Pro - viron. If severe upper abdominal complaints, liver enlargement or signs of intra-abdominal haemorrhage occur, the possibility of a liver tumour should be included in the differential diagnosis.

Frequent or persistent erections of the penis may occur (see section 4.8 “Undesirable effects”).

None known.

Not applicable.

None known.

If, in individual cases, frequent or persistent erections occur, the dose should be discontinued in order to avoid injury to the penis.

There have been no reports of ill-effects from overdosage and treatment is generally unncessary. If overdosage is discovered within two to three hours and is so large that treatment seems desirable, gastric lavage can safely be used.

Pro-viron is an orally active androgen.The presence of a methyl group at C-1 confers special properties on this steroid which, unlike testosterone and all its derivatives that are used for androgen therapy, is not metabolised to oestrogen.

This difference almost certainly accounts for the observation that, in its usual therapeutic dosage in normal men, Pro-viron does not significantly depress the release of gonadotrophins from the pituitary. Hence (1) spermatogenesis is unimpaired (2) unlike other androgens, which suppress and therefore replace endogenous androgens, Pro-viron supplements endogenous androgens.

In contrast to other orally active androgens, liver tolerance is excellent (a fact probably related to the absence of 17-alkyl substitution of the steroid nucleus).

Following oral ingestion mesterolone is rapidly and almost completely absorbed in a wide dose range of 25 - 100 mg. The intake of Pro-viron generates maximum serum drug levels of 3.1 ± 1.1 ng/ml after 1.6 ± 0.6 hours. Thereafter, drug levels in serum decrease with a terminal half-life of 12 - 13 hours. Mesterolone is 98% bound to serum proteins., 40% to albumin and 58% to SHBG (sex hormone binding globulin).

Mesterolone is rapidly inactivated by metabolism. The metabolic clearance rate from serum accounts for 4.4 ± 1.6 ml·min^-1·kg^-1. There is no renal excretion of unchanged drug. The main metabolite has been identified as 1α-methyl-androsterone, which - in conjugated form - accounts for 55 - 70 % of renally excreted metabolites. The ratio of the main metabolite glucuronide to sulphate is about 12:1. A further metabolite 1α-methyl-5α-androstane-3α,17β-diol has been recognized, which accounted for about 3 % of renally eliminated metabolites. No metabolic conversion into oestrogens or corticoids has been observed. 77% of the mesterolone metabolites are excreted via the urine and 13% with the faeces. 50% of the dose is excreted in the urine within 24 hours and 90% within 7 days via the faeces and urine.

The absolute bioavailability of mesterolone is about 3 % of the oral dose.

There are no preclinical data which could be of relevance to the prescriber and which are not already included in other relevant sections of the SPC.

Lactose

maize starch

povidone 25 000 (E1201)

methyl parahydroxybenzoate (E218)

propyl parahydroxybenzoate (E216)

magnesium stearate (E572)

None known.

5 years.

None

3 blister packs of 10 tablets contained in a cardboard outer pack.

Store all drugs properly and keep them out of reach of children.

Bayer plc

Bayer House

Strawberry Hill

Newbury

Berkshire RG14 1JA

United Kingdom

PL 00010/0562

Date of first authorisation: 1^st May 2008

30 March 2012