Pharmacodynamics Penbutolol is able to bind to both beta-1 adrenergic receptors and
beta-2 adrenergic receptors (the two subtypes), thus making it a non-selective β blocker. Penbutolol acts on the β1 adrenergic receptors in both the heart and the kidney. When β1 receptors are activated by a
catecholamine, they stimulate a coupled
G protein which activates adenylyl to convert
adenosine triphosphate (ATP) to
cyclic adenosine monophosphate (cAMP). The increase in cAMP ultimately alters the movement of calcium ions in heart muscle and increases heart rate. The ability of penbutolol to act as a
partial agonist proves useful in the prevention of
bradycardia as a result of decreasing the heart rate excessively. Like
propranolol and
pindolol, it is a
serotonin 5-HT1A and
5-HT1B receptor antagonist; this discovery by several groups in the 1980s generated excitement among those doing research on the serotonin system as such antagonists were rare at that time.
Pharmacokinetics Penbutolol is rapidly absorbed from the gastrointestinal tract, has a
bioavailability over 90%, and has a rapid onset of effect. Penbutolol has a
half life of five hours. ==Chemistry==