Carbapenems can only be given through an intravenous drip, which usually does not cause irritation at the injection site. If you have a severe allergy to penicillin, you generally should not be given a carbapenem. However, many patients with a mild or moderate allergy can tolerate carbapenems.
Alpha-1 adrenergic agonists. Alpha-1 adrenergic agonists stimulate alpha-1 receptors coupled to G proteins and phospholipase C. They can be classified in two groups: those which do not cross the blood-brain barrier and have peripheral effects and those which penetrate into the brain and have mainly central effects. Alpha-1 agonists with peripheral effects.
Strictly speaking, agonist & antagonist refer to the action of a molecule at a receptor. An agonist molecule produces the same effect as whatever molecule normally binds to that receptor. An antagonist molecule blocks the effects of the molecule that normally binds to that receptor. An inverse agonist produces the opposite effect to the molecule that normally binds to a receptor.