basics of pharmacokinetics

# Pharmacokinetics equations describe the relationships between the dosage regimen and the profile of drug concentration in the blood over time.

# Pharmacodynamic equations describe the relationships between the drug concentration-time profile and therapeutic and adverse effects.

## Initial Treatment

# volume of distribution
volume (V) = D / C
D: dose, C: concentration

# target concentration
Loading dose = (Target C - Measured C)*V

# salt correction factor (s)
# molar correction factor (m)

## Continuing Treatment

# Maintenance dose and clearance
Css (steady state concentation) = (s*m*IR) / CI
CI: clearance rate, IR: infusion rate

# Factors affecting clearance
# Bioavailability and oral maintenance dosage regiments
bioavailability: the proportion of the administered dose that reaches the systemic circulation
Css average = Dosing rate / CI = F*D*s*m / (CI*tau)
Oral Dose = (target Css average * CI*tau) / (F*s*m)
tau: dosage interval, F: bioavailability

## Stopping Treatment

# Elimination rate constant (k) and concentration-time profile
Ct = (D/V)*exp(-kt)
Ct: concentration at any time after the dose
D/V: maximum concentration that would be achieved

#Elimination half-life
t(1/2) = ln(2)/k

From "Back to basics: pharmacokinetics by Alison Thomson"