Yes. In healthy adults, oral psilocybin appears to be rapidly converted to psilocin, and psilocin shows approximately linear pharmacokinetics across 0.3 to 0.6 mg/kg, based on an open-label dose-escalation study (details here).
In that study, intact psilocybin was not measurable in plasma or urine, indicating fast conversion. Psilocin had an average elimination half-life near 3 hours, and renal excretion of unchanged psilocin accounted for less than 2 percent of total clearance. Some participants showed a prolonged terminal phase, consistent with breakdown of a glucuronide metabolite.
Body weight did not reliably predict psilocin clearance. Using the pharmacokinetic parameters, the authors simulated that a fixed 25 mg oral dose would yield exposure similar to 0.3 mg/kg. These results come from a small study in healthy volunteers and do not establish clinical efficacy or dosing guidance.
In short, psilocybin is rapidly converted to psilocin, and psilocin displays linear kinetics over the studied dose range.