Pharmacodynamics active drug fraction

The clinical pharmacodynamics and pharmacokinetics of molindone (91) have been reviewed (525). The drug is reputed to be rapidly absorbed after oral administration and rapidly metabolized. Only 2-3% of the unchanged drug can be recovered in the urine and feces. Molindone has a very short half-like (1.5-2 h) and is 1.5-1.7 times more bioavailable after intramuscular, rather than oral, administration (526). Molindone is less lipophilic than most antipsychotic drugs and has a lower fraction (around 75%)that is bound to proteins in the plasma (527).Clinical studies indicate that the antipsychotic effectiveness of molindone lasts more than 24 h (525,528,5291, suggesting that one or more active metabolites may contribute to its actions in vivo. 

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