# Thymosin Alpha-1 Dosage in the Research Literature > Thymosin alpha-1 dosage as documented in trials: 1.6 mg subcutaneously twice weekly (hepatitis), 1.6 mg BID then daily (sepsis ETASS), 900 μg twice weekly (vaccine adjuvant). Documented trial protocols, pharmacokinetics, and administration routes — not a personal dosing recommendation. ## Reading Thymosin alpha-1 dosage protocols from the trial record Thymosin alpha-1 dosage in the published trial record is unusually consistent. The standard branded regimen — used in the hepatitis approval-anchoring trials — is 1.6 mg subcutaneously twice weekly [20]. Sepsis trials use the same 1.6 mg subcutaneous unit dose but compress the schedule (twice daily for 5 days, then daily for 2 days) [6]. Oncology adjuvant trials have varied dose and schedule. Vaccine-adjuvant protocols use lower doses (900 μg twice weekly × 4 weeks) [18]. All approved-indication trials use subcutaneous administration; oral bioavailability is essentially zero because the peptide is hydrolyzed in the gastric environment. ## Published Dosing Protocols The published dosing protocols cluster into five regimens: 1. **Chronic hepatitis B and C**: 1.6 mg subcutaneously twice weekly for 6 months [12][13][14]. 2. **Severe sepsis (ETASS protocol)**: 1.6 mg subcutaneously twice daily for 5 days, then 1.6 mg subcutaneously once daily for 2 days [6]. 3. **Severe COVID-19**: 1.6 mg subcutaneously once daily, with earlier initiation associated with stronger mortality signal [8][9]. 4. **Influenza vaccine adjuvant (Gravenstein 1989)**: 900 μg subcutaneously twice weekly for 4 weeks plus inactivated influenza vaccine [18]. 5. **Post-transplant immune reconstitution (Perruccio 2010)**: 1.6 mg subcutaneously twice weekly post-transplant [19]. ## Reported Dose Ranges Trial doses range from 900 μg to 16 mg subcutaneously, with 1.6 mg twice weekly the most commonly studied unit dose in chronic indications [20]. Higher unit doses appear in early-phase oncology adjuvant studies; no dose-limiting toxicity has been reported up to 16 mg subcutaneous. The 1.6 mg dose anchors the Zadaxin label-equivalent regimen and has been the comparator dose for most subsequent trials. ## Acute Illness Dosing Protocols in the Literature For **thymosin alpha 1 dosage when sick**, the published acute-illness protocols are the sepsis and COVID-19 regimens — both intentionally front-loaded relative to the chronic hepatitis schedule. The ETASS sepsis trial protocol administered 1.6 mg subcutaneously twice daily for the first 5 days then once daily for 2 days, total 7 days [6]. The Liu 2020 Wuhan COVID-19 cohort administered 1.6 mg subcutaneously once daily [8]; the Sun 2021 critical-COVID-19 study used the same daily dosing with earlier initiation favored [9]. These are inpatient protocols administered under medical supervision in trial settings. They are described here as documented trial protocols, not as a recommendation for outpatient acute use. ## Treatment Duration in the Literature Hepatitis B and C trials typically dosed for 6 months [12][14]. The ETASS sepsis protocol ran 7 days [6]. Influenza-vaccine-adjuvant protocols ran 4 weeks [18]. Post-transplant immune-reconstitution dosing in the Perruccio cohort extended across the post-transplant recovery window [19]. No consensus protocol exists for non-trial outpatient use; the durations above reflect the documented trial designs. ## Pharmacokinetics and Half-Life Plasma elimination half-life after subcutaneous administration is approximately 2 hours in healthy adults, as documented in the Billich 2001 pharmacy monograph and the underlying Zadaxin development PK work [20]. Biological immunomodulatory effect persists 48–72 hours — the rationale for the twice-weekly hepatitis schedule despite the short plasma half-life. Receptor engagement (TLR-9 / TLR-2 on dendritic cells) initiates downstream T-cell and cytokine cascades that outlast plasma presence by orders of magnitude [4][5]. A 2025 preclinical study in Drug Delivery (Hu et al.) reported development of an in-situ-forming liquid-crystal depot intended to extend Tα1 subcutaneous dosing intervals beyond twice-weekly — an in vitro release-profile study, not a clinical trial [24]. ## Routes of Administration in Studies Subcutaneous injection is the standard route in every approved-indication trial [20]. Intravenous administration has appeared in early-phase exploratory work but is not the standard. Intramuscular administration appears in some legacy formulations. Oral administration has been investigated preclinically but is not bioavailable — the synthetic peptide is hydrolyzed in the gastric environment. ## How Thymosin Alpha-1 Is Administered in Trials Subcutaneous injection of the reconstituted lyophilized synthetic peptide is the standard. Reconstituted product is intended for prompt administration per the Zadaxin product label [20]. Injection sites in the published trials are typically abdomen or thigh; injection-site discomfort and transient erythema are the most commonly reported adverse events across the published Zadaxin program. ## Timing of Administration Most trials administered without regard to circadian timing; twice-weekly dosing was selected based on the peptide's pharmacokinetic half-life and the duration of downstream biological effect rather than on chronobiology [20]. The sepsis twice-daily-for-5-days protocol is exposure-driven: it maintains dendritic-cell receptor engagement across the critical early window of sepsis-induced immune suppression [6]. --- Chalked up, erased, and chalked back again — a classroom-style review of the published Thymosin alpha-1 literature, not a clinical recommendation.