2. Distribution Flashcards
what is the APPARENT VOLUME of DISTRIBUTION (Vd)
HYPOTHETICAL VOLUME in which the DRUG is DISSOLVED AFTER ABSORPTION
how to CALCULATE VOLUME of DISTRIBUTION (Vd)
Relates AMOUNT of DRUG IN BODY to the CONCENTRATION of DRUG IN BLOOD
Vd = AMOUNT IN BODY / CONC.
= DOSE / INITIAL CONC.
If DRUG is avidly BOUND in TISSUES, how is Vd
LOW CONC. in PLASMA
so Vd may greatly EXCEED TOTAL BODY WATER
- HIGH Vd
if DRUG is HIGHLY BOUND in PLASMA, how is Vd
high plasma conc. so LOW Vd
Vd will APPROACH PLASMA VOLUME
DRUG CONCENTRATION =
DOSE / VOLUME
how is VOLUME OF DISTRIBUTION if PLASMA CONC. of drug is HIGH
LOW VOLUME of DISTRIBUTION
how is VOLUME OF DISTRIBUTION if PLASMA CONC. of drug is LOW and more drug is in the rest of the BODY
HIGH VOLUME of DISTRIBUTION
Examples of KEY BINDING PROTEINS that may bind and affect ability of drugs to penetrate in organs/tissues
Albumin
Alpha 1-Acid Glycoprotein
CBG (Corticosteroid Binding Globulin)
SHBG (Sex Hormone Binding Globulin)
FACTORS REGULATING DRUG PENETRATION in TISSUES (can influence)
DRUG CHARACTERISTICS:
- drug LIPOPHILICITY (affinity of a drug for a lipid environment / dissolving in lipids)
- POLARITY
- PROTEIN BINDING
FACTORS REGULATING DRUG PENETRATION in TISSUES (can influence)
Other Molecules:
- UPTAKE TRANSPORTERS
- EFFLUX TRANSPORTERS
- EQUILIBRATING TRANSPORTER
(can balance passive diffusion of lipophilic non-polar drugs, back in)
eg P-gP Transporter (for DRUG EFFLUX)
where in the Body are especially characterised by ANATOMICAL BARRIERS (more resistant in capillaries to penetration of chemicals)
BRAIN (BLOOD-BRAIN BARRIER)
& GENITALS
what in patients can INFLUENCE VOLUME of DISTRIUTION
PATEINT CHARACTERISTICS
eg Pregnancy, Obesity, Co-Morbidities
VOLUME of DISTRIBUTION / DRUG DISTRIBUTION has an influence on .. profile
Pharmacokinetic Profile
DRUG DISTRIBUTION is a central process INFLUENCING..
TOXICITY and EFFICACY
what else can be influenced by Drug VOLUME of DISTRIBUTION
Selection of DOSING REGIMENS
