Pharmacokinetics (ADME)

Pharmacokinetics refers to how a drug moves through the body over time. The four stages of this process—Absorption, Distribution, Metabolism, and Excretion (ADME)—determine how efficiently and for how long an anabolic steroid exerts its effects.

Understanding ADME is critical for:

Planning dose timing and injection frequency
Managing oral vs. injectable differences
Anticipating side effects and toxicity
Timing bloodwork and post-cycle therapy (PCT)

A – Absorption

Absorption refers to how the steroid enters the bloodstream after administration. It depends on the route of administration (oral, intramuscular, subcutaneous) and formulation (ester, alkylation, carrier oil).

Route	Characteristics	Bioavailability
Oral (e.g., Dianabol, Superdrol)	Rapid absorption via GI tract	Low to moderate (5–30%)
Injectable (e.g., Test E, Deca)	Depot formation in muscle; slow release	~100%
Subcutaneous (e.g., hCG, peptides)	Diffuses through fat into blood	High
Buccal/Nasal (rare for AAS)	Direct to bloodstream via mucosa	High, but rarely used for steroids

Key Points:

C17α-alkylation allows oral steroids to survive first-pass liver metabolism
Injectables bypass the liver on first pass, reducing hepatic stress
Absorption rate of injectables is heavily influenced by ester length and injection site

D – Distribution

Once in the bloodstream, the steroid is distributed to tissues throughout the body. Steroids are lipophilic, meaning they tend to accumulate in fat and muscle tissues.

Bind to sex hormone-binding globulin (SHBG) and albumin
Only free hormone is biologically active
Higher doses = more free hormone saturation = more anabolic effect

Factors influencing distribution:

Plasma protein binding affinity
Muscle mass and fat percentage
Concurrent medications or supplements (e.g., competing for albumin)

Note: Some steroids (e.g., Trenbolone) exhibit high tissue affinity, leading to more potent effects at lower serum levels.

M – Metabolism

Metabolism refers to the chemical modification of the steroid, primarily in the liver. The liver converts active steroids into inactive metabolites for eventual excretion.

Key metabolic processes:

Phase I (modification): Hydroxylation, oxidation, reduction
Phase II (conjugation): Glucuronidation, sulfation

Compound Class	Liver Metabolism	Notes
C17α-alkylated orals	High hepatotoxicity risk	Use TUDCA/NAC; short durations only
Injectable steroids (non-alkylated)	Mild liver impact	Lower concern unless stacked with orals
DHT-derivatives (e.g., Winstrol, Masteron)	Unique reduction pathways	May have poor aromatization profiles

Enzyme Impact:

CYP450 enzymes (especially CYP3A4) are responsible for steroid breakdown
Certain drugs (e.g., grapefruit juice, antifungals) may inhibit or accelerate steroid metabolism

E – Excretion

Steroids are excreted primarily via:

Urine (major pathway)
Bile and feces (minor)
Sweat (trace)

Once metabolized by the liver, conjugated steroid metabolites are excreted by the kidneys. Drug detection times depend on:

Ester length (see: esters_and_half_lives)
Fat solubility
Frequency and duration of use

Compound	Detection Time (approx.)	Notes
Testosterone Propionate	~2–3 weeks	Short ester, fast clearance
Testosterone Enanthate	~3–4 weeks	Moderate ester
Nandrolone Decanoate	~18 months	Long half-life and lipophilicity
Oral Turinabol	~40–50 days	Active metabolite detectable for weeks

Tip: Long esters and fat-soluble compounds persist longer and delay PCT start time.

Practical Implications for Bodybuilders

Timing injections based on absorption and ester clearance is key to stable hormone levels
Metabolism rate varies—some users clear orals rapidly, others accumulate liver strain
Drug testing windows vary wildly based on ADME properties
PCT planning should always account for metabolic clearance

Real-World Advice (r/steroids PDF)

“My orals kick in fast, but crash just as fast. Timing matters.”
“I ran Deca without waiting long enough for PCT—never again.”
“Always pin test E every 3.5 days. Once a week gave me mood swings.”
“Bloodwork timing is everything—wait until esters clear or your labs will lie.”

Summary

Absorption = how fast the compound enters the blood
Distribution = where the steroid travels and accumulates
Metabolism = how the body modifies and deactivates the steroid
Excretion = how the steroid leaves the body

Understanding the pharmacokinetics of AAS empowers users to plan smarter cycles, avoid toxicity, and support long-term health.