SC vs IM Detailed Study Analysis

Hey guys,

I’m considering SC TRT. Most detailed & recent study I’ve found: Pharmacokinetic Profile of Subcutaneous Testosterone Enanthate Delivered via a Novel, Prefilled Single‐Use Autoinjector: A Phase II Study - PMC

Participants: 38 healthy men with hypo; AVG: 53 years old, 92 kg of weight, 178 cm of height (BMI = 29, obesity);

14 of them were treated with 50 mg SC TE 1/ew, 15 with 100 mg SC TE 1/ew, 10 with 200 mg IM TE 1/ew.

T AUC0>168h:

SC50 = 71k
SC100 = 150k
IM200 = 280k

SC100:SC50 = 2.13
IM200:SC100 = 1.85

T cAVG0>168h:

SC50 = 422
SC100 = 895
IM200 = 1660

SC100:SC50 = 2.12
IM200:SC100 = 1.85

(AUC reflection; conclusion: SC injection saves ~8% of the drug because of it’s slower TE release from the tissue, it’s logical if we look at SC’s t1/2 and AUC0>168h; both routes have the same BV basing on their AUC0>inf)


SC50 = 622 (range 388 - 825)
SC100 = 1346 (624 - 2120)
IM200 = 2262 (787 - 4840)

SC100:SC50 = 2.17
IM200:SC100 = 1.7

(looking at AVG we could conclude that we’d get bigger T spike during SC, but when looking at ranges we assume that the difference is irrelevant = aromatization rate should be the same with SC100 and IM100)


SC50 = 273 (182 - 372)
SC100 = 568 (236 - 860)
IM200 = 466 (203 - 780)

SC100:SC50 = 2.1
IM200:SC100 = 0.8

(2x higher cMIN with SC; conclusion: slower TE release with SC)

T tMAX was the same for both SC100 and IM200.

T t1/2:

SC50 = ND
SC100 = 10 days
IM200 = 7 days

(t1/2 is 30% higher with SC; conclusion: slower release of TE with SC)

DHT/T ratio was the same with SC50, SC100 and IM200.

E2 cAVG0>168h:

SC50 = 25.6 (E2:T 0.0063)
SC100 = 48.3 (0.0055)
IM200 = 50.0 (0.0032)

(it seems that aromatization is 2x more potent with SC)


SC route of the drug administration provides us obviously less pain & no muscle damage during injection, increased T t1/2 by 30% (so higher T cMIN) and the same: BV, T spikes, DHT/T ratio, T tmax. The depressing fact is 100 mg of TE SC produced the same level of E2 as 200 mg of TE IM. It’s 2x more!

Isn’t that irrational? Despite the longer t1/2 (which is obviously better considering aromatization) with SC, almost all PK parameters were the same. As we know aromatization rate is relatively high in fatty tissue, BUT the enzyme actually can’t convert enanthate ester to E2 before hydrolysis of the chemical bond what happen in the blood. I don’t see any serious reason for that E2 inconvenience.

Thanks for that link.

Administration of TE via this novel injection system restored T levels to normal range in men with hypogonadism. SC TE dosed weekly demonstrated steady, dose‐proportional measures of exposure and was well‐tolerated. Kaminetsky J, Jaffe JS, Swerdloff RS. Pharmacokinetic profile of subcutaneous testosterone enanthate delivered via a novel, prefilled single‐use autoinjector: A phase II study. Sex Med 2015;3:263–273.

Does anyone take as much as 1mL sub Q?

SC and IM have almost nothing to do with anything beside the gauge and length of the needle a guy chooses to use. Anything else is anecdotal and subjective at the very best.

SC’s blood flow is worse than IM’s and difference is significant - PK parameters as t1/2 and AUC0>168h confirm that perfectly. Some guys feel better after switching to SC, some feel worse. From my experience, only few of them can properly manage their E2 levels and really understand TE’s pharmacokinetics, so the symptoms.

The problem is, presented study is the only rich in PK parameters currently available. High E2 result with SC is absolutely illogical. What remains is experiencing on ourselves, inconveniently. I’ve personally started with 50 mg UG TE with 250 UI of hCG both EOD SC without an AI hoping I won’t need that with E2 in 25-30 pg/mL (my personal sweet spot). After more than 1 week with frontload I feel perfectly, no symptoms of high E2, but it’s too early to judge. I’ll let you know.