Testosterone buciclate

Testosterone buciclate (developmental code names 20 Aet-1, CDB-1781) is a synthetic, injected anabolic–androgenic steroid (AAS) which was never marketed.[3][4][5] It was developed in collaboration by the Contraceptive Development Branch (CDB) of the National Institute of Child Health and Human Development (NICHD) and the World Health Organization (WHO) in the 1970s and early 1980s for use in androgen replacement therapy for male hypogonadism and as a potential male contraceptive.[3] It was first described in 1986.[4] The medication is an androgen ester – specifically, the C17β buciclate (4-butylcyclohexane-1-carboxylate) ester of testosterone – and is a prodrug of testosterone with a very long duration of action when used as a depot via intramuscular injection.[3][6] Testosterone buciclate is formulated as a microcrystalline aqueous suspension with a defined particle size of at least 75% in the range of 10 to 50 μm.[7]

Testosterone buciclate
Testosteronebuciclate structure.png
Testosterone buciclate molecule ball.png
Clinical data
Other namesTestosterone bucyclate; Testosterone 17β-buciclate; 20 Aet-1; CDB-1781; Testosterone 17β-(trans-4-butylcyclohexyl)carboxylate
Routes of
Intramuscular injection
Drug classAndrogen; Anabolic steroid; Androgen ester
Pharmacokinetic data
BioavailabilityOral: very low
Intramuscular: very high
Elimination half-lifeTea seed oil: 20.9 days (i.m.)[1][2]
Castor oil: 33.9 days (i.m.)[1][2]
CAS Number
PubChem CID
CompTox Dashboard (EPA)
Chemical and physical data
Molar mass454.695 g·mol−1
3D model (JSmol)

A single intramuscular injection of testosterone buciclate has been found to produce physiological levels of testosterone within the normal range in hypogonadal men for 3 to 4 months.[3][1][8][9][2] The elimination half-life and mean residence time (average amount of time a single molecule of drug stays in the body) of testosterone buciclate were found to be 29.5 days and 60.0 days, respectively, whereas those of testosterone enanthate in castor oil were only 4.5 days and 8.5 days.[8][9][2] Testosterone buciclate also lasts longer than testosterone undecanoate, which has elimination half-lives and mean residence times of 20.9 days and 34.9 days in tea seed oil and 33.9 days and 36.0 days in castor oil, respectively.[1][9][2] In addition, there is a spike in testosterone levels with testosterone enanthate and testosterone undecanoate that is not seen with testosterone buciclate, with which levels stay highly uniform and decrease very gradually and progressively.[1] Testosterone buciclate can maintain testosterone levels in the normal male range for up to 20 weeks with a single intramuscular injection.[10]

Testosterone buciclate is able to reversibly and completely suppress spermatogenesis in men when used at sufficiently high dosages.[8] As such, the results of clinical studies for use of testosterone buciclate as a male contraceptive were promising, and trials continued as late as 1995,[11] but progress ultimately came to a standstill because the WHO was unable to find an industry partner willing to continue the development of the drug.[1] Because of this, the WHO backed away from testosterone buciclate and focused its research instead on testosterone undecanoate, which is also very long-lasting and has the advantage of having already been marketed and approved for medical use.[12]

Androgen replacement therapy formulations and dosages used in men
Route Medication Major brand names Form Dosage
Oral Testosteronea Tablet 400–800 mg/day (in divided doses)
Testosterone undecanoate Andriol, Jatenzo Capsule 40–80 mg/2–4x day (with meals)
Methyltestosteroneb Android, Metandren, Testred Tablet 10–50 mg/day
Fluoxymesteroneb Halotestin, Ora-Testryl, Ultandren Tablet 5–20 mg/day
Metandienoneb Dianabol Tablet 5–15 mg/day
Mesteroloneb Proviron Tablet 25–150 mg/day
Buccal Testosterone Striant Tablet 30 mg 2x/day
Methyltestosteroneb Metandren, Oreton Methyl Tablet 5–25 mg/day
Sublingual Testosteroneb Testoral Tablet 5–10 mg 1–4x/day
Methyltestosteroneb Metandren, Oreton Methyl Tablet 10–30 mg/day
Intranasal Testosterone Natesto Nasal spray 11 mg 3x/day
Transdermal Testosterone AndroGel, Testim, TestoGel Gel 25–125 mg/day
Androderm, AndroPatch, TestoPatch Non-scrotal patch 2.5–15 mg/day
Testoderm Scrotal patch 4–6 mg/day
Axiron Axillary solution 30–120 mg/day
Androstanolone (DHT) Andractim Gel 100–250 mg/day
Rectal Testosterone Rektandron, Testosteronb Suppository 40 mg 2–3x/day
Injection (IM or SC) Testosterone Andronaq, Sterotate, Virosterone Aqueous suspension 10–50 mg 2–3x/week
Testosterone propionateb Testoviron Oil solution 10–50 mg 2–3x/week
Testosterone enanthate Delatestryl Oil solution 50–250 mg 1x/1–4 weeks
Xyosted Auto-injector 50–100 mg 1x/week
Testosterone cypionate Depo-Testosterone Oil solution 50–250 mg 1x/1–4 weeks
Testosterone isobutyrate Agovirin Depot Aqueous suspension 50–100 mg 1x/1–2 weeks
Testosterone phenylacetateb Perandren, Androject Oil solution 50–200 mg 1x/3–5 weeks
Mixed testosterone esters Sustanon 100, Sustanon 250 Oil solution 50–250 mg 1x/2–4 weeks
Testosterone undecanoate Aveed, Nebido Oil solution 750–1,000 mg 1x/10–14 weeks
Testosterone buciclatea Aqueous suspension 600–1,000 mg 1x/12–20 weeks
Implant Testosterone Testopel Pellet 150–1,200 mg/3–6 months
Notes: Men produce about 3 to 11 mg testosterone per day (mean 7 mg/day in young men). Footnotes: a = Never marketed. b = No longer used and/or no longer marketed. Sources: See template.
Pharmacokinetics of testosterone esters
Testosterone ester Form Route Tmax t1/2 MRT
Testosterone undecanoate Oil-filled capsules Oral ? 1.6 hours 3.7 hours
Testosterone propionate Oil solution Intramuscular injection ? 0.8 days 1.5 days
Testosterone enanthate Castor oil solution Intramuscular injection 10 days 4.5 days 8.5 days
Testosterone undecanoate Tea seed oil solution Intramuscular injection 13.0 days 20.9 days 34.9 days
Testosterone undecanoate Castor oil solution Intramuscular injection 11.4 days 33.9 days 36.0 days
Testosterone buciclatea Aqueous suspension Intramuscular injection 25.8 days 29.5 days 60.0 days
Notes: Testosterone cypionate has similar pharmacokinetics to TE. Footnotes: a = Never marketed. Sources: See template.
Parenteral durations of androgens/anabolic steroids
Medication Form Major brand names Duration
Testosterone Aqueous suspension Andronaq, Sterotate, Virosterone 2–3 days
Testosterone propionate Oil solution Androteston, Perandren, Testoviron 3–4 days
Testosterone phenylpropionate Oil solution Testolent 8 days
Testosterone isobutyrate Aqueous suspension Agovirin Depot, Perandren M 14 days
Mixed testosterone estersa Oil solution Triolandren 10–20 days
Mixed testosterone estersb Oil solution Testosid Depot 14–20 days
Testosterone enanthate Oil solution Delatestryl 14–28 days
Testosterone cypionate Oil solution Depovirin 14–28 days
Mixed testosterone estersc Oil solution Sustanon 250 28 days
Testosterone undecanoate Oil solution Aveed, Nebido 100 days
Testosterone buciclated Aqueous suspension 20 Aet-1, CDB-1781e 90–120 days
Nandrolone phenylpropionate Oil solution Durabolin 10 days
Nandrolone decanoate Oil solution Deca Durabolin 21–28 days
Methandriol Aqueous suspension Notandron, Protandren 8 days
Methandriol bisenanthoyl acetate Oil solution Notandron Depot 16 days
Metenolone acetate Oil solution Primobolan 3 days
Metenolone enanthate Oil solution Primobolan Depot 14 days
Note: All are via i.m. injection. Footnotes: a = TP, TV, and TUe. b = TP and TKL. c = TP, TPP, TiCa, and TD. d = Studied but never marketed. e = Developmental code names. Sources: See template.
Structural properties of major testosterone esters
Androgen Structure Ester Relative
mol. weight
T contentb
Position Moiety Type Lengtha Rank Group
Testosterone Testosteron.svg 1.00 1.00 11 Short
Testosterone propionate Testosterone propionate.svg C17β Propanoic acid Straight-chain fatty acid 3 1.19 0.84 10 Short
Testosterone isobutyrate Testosterone isobutyrate.svg C17β Isobutyric acid Aromatic fatty acid – (~3) 1.24 0.80 9 Moderate
Testosterone cypionate Testosterone cypionate.svg C17β Cyclopentylpropanoic acid Aromatic fatty acid – (~6) 1.43 0.70 8 Moderate
Testosterone phenylpropionate Testosterone phenpropionate.svg C17β Phenylpropanoic acid Aromatic fatty acid – (~6) 1.46 0.69 7 Moderate
Testosterone isocaproate Testosterone isocaproate.svg C17β Isohexanoic acid Branched-chain fatty acid – (~5) 1.34 0.75 6 Moderate
Testosterone caproate Testosterone caproate.svg C17β Hexanoic acid Straight-chain fatty acid 6 1.35 0.75 5 Moderate
Testosterone enanthate Testosterone enanthate.svg C17β Heptanoic acid Straight-chain fatty acid 7 1.39 0.72 4 Moderate
Testosterone decanoate Testosterone decanoate.svg C17β Decanoic acid Straight-chain fatty acid 10 1.53 0.65 3 Long
Testosterone undecanoate Testosterone undecanoate.svg C17β Undecanoic acid Straight-chain fatty acid 11 1.58 0.63 2 Long
Testosterone buciclated Testosteronebuciclate structure.png C17β Bucyclic acide Aromatic carboxylic acid – (~9) 1.58 0.63 1 Long
Footnotes: a = Length of ester in carbon atoms for straight-chain fatty acids or approximate length of ester in carbon atoms for aromatic fatty acids. b = Relative testosterone content by weight (i.e., relative androgenic/anabolic potency). c = Duration by intramuscular or subcutaneous injection in oil solution (except TiB and TB, which are in aqueous suspension). d = Never marketed. e = Bucyclic acid = trans-4-Butylcyclohexane-1-carboxylic acid. Sources: See individual articles.

See alsoEdit


  1. ^ a b c d e f Eberhard Nieschlag; Hermann Behre (29 June 2013). Andrology: Male Reproductive Health and Dysfunction. Springer Science & Business Media. pp. 316, 412. ISBN 978-3-662-04491-9.
  2. ^ a b c d e Behre HM, Abshagen K, Oettel M, Hübler D, Nieschlag E (1999). "Intramuscular injection of testosterone undecanoate for the treatment of male hypogonadism: phase I studies". Eur. J. Endocrinol. 140 (5): 414–9. CiteSeerX doi:10.1530/eje.0.1400414. PMID 10229906.
  3. ^ a b c d C. Coutifaris; L. Mastroianni (15 August 1997). New Horizons in Reproductive Medicine. CRC Press. pp. 100–. ISBN 978-1-85070-793-6.
  4. ^ a b William Llewellyn (2009). Anabolics. Molecular Nutrition Llc. pp. 138–140. ISBN 978-0967930473.
  5. ^ Behre HM, Nieschlag E (1992). "Testosterone buciclate (20 Aet-1) in hypogonadal men: pharmacokinetics and pharmacodynamics of the new long-acting androgen ester". J. Clin. Endocrinol. Metab. 75 (5): 1204–10. doi:10.1210/jcem.75.5.1430080. PMID 1430080.
  6. ^ Shalender Bhasin (13 February 1996). Pharmacology, Biology, and Clinical Applications of Androgens: Current Status and Future Prospects. John Wiley & Sons. pp. 472–. ISBN 978-0-471-13320-9.
  7. ^ Hermann M. Behre; Gerhard F. Weinbauer; Eberhard Nieschlag (13 February 1996). "Testosterone Buciclate". In Shalender Bhasin; Henry L. Gabelnick; Jeffrey M. Spieler (eds.). Pharmacology, Biology, and Clinical Applications of Androgens: Current Status and Future Prospects. John Wiley & Sons. pp. 471–480. ISBN 978-0-471-13320-9. Testosterone buciclate is applied intramuscularly as a microcrystalline aqueous suspension. [...] After air milling [...] of crystalline testosterone buciclate to a particle size of at least 75% in the range of 10 - 50 μm, the drug was [...] suspended in sterile, aqueous suspension vehicle [...].
  8. ^ a b c Anita H. Payne; Matthew P. Hardy (28 October 2007). The Leydig Cell in Health and Disease. Springer Science & Business Media. pp. 423–. ISBN 978-1-59745-453-7.
  9. ^ a b c Eberhard Nieschlag; Hermann M. Behre; Susan Nieschlag (13 January 2010). Andrology: Male Reproductive Health and Dysfunction. Springer Science & Business Media. pp. 441–446. ISBN 978-3-540-78355-8.
  10. ^ Carrie Bagatell; William J. Bremner (27 May 2003). Androgens in Health and Disease. Springer Science & Business Media. pp. 146–. ISBN 978-1-59259-388-0.
  11. ^ Behre HM, Baus S, Kliesch S, Keck C, Simoni M, Nieschlag E (1995). "Potential of testosterone buciclate for male contraception: endocrine differences between responders and nonresponders". J. Clin. Endocrinol. Metab. 80 (8): 2394–403. doi:10.1210/jcem.80.8.7543113. PMID 7543113.
  12. ^ Nieschlag E, Kumar N, Sitruk-Ware R (2013). "7α-methyl-19-nortestosterone (MENTR): the population council's contribution to research on male contraception and treatment of hypogonadism". Contraception. 87 (3): 288–95. doi:10.1016/j.contraception.2012.08.036. PMID 23063338.