Laadimised

Laadimised (loading doses) are an initial higher dose administered to rapidly achieve therapeutic drug concentrations in the bloodstream. They are used for drugs with long half-lives, large volumes of distribution, poor tissue penetration, or when rapid onset is required, to shorten the time to reach steady-state concentrations above the minimum effective concentration.

The loading dose is calculated from pharmacokinetic parameters. For intravenous or oral administration, the loading dose approximates the target concentration multiplied by the volume of distribution and divided by bioavailability: LD ≈ (Ctarget × Vd) / F. After the loading dose, maintenance dosing is used to keep concentrations within the therapeutic range: MD ≈ (Ctarget × Cl × τ) / F, where Cl is clearance and τ is the dosing interval.

Planning for laadimised considers drug properties, patient factors (age, weight, organ function), route of administration, and risk of toxicity. In drugs with narrow therapeutic indices or unpredictable pharmacokinetics, loading doses require careful assessment and sometimes therapeutic drug monitoring.

Monitoring and safety are important: loading doses require monitoring of drug levels when available, as well as renal and hepatic function and clinical response. Dose adjustments may follow trough level measurements and adverse effects.

Examples of use include antibiotics such as vancomycin and aminoglycosides, certain antiretrovirals and antifungals, and some chemotherapeutic agents where rapid achievement of effective levels is desirable.