====== 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.