An example of covalent drug receptor interaction:
Phenoxybenamine is an irreversible (covalent) antagonist at alpha receptors. All other drugs mentioned are reversibly interacting with their receptors.
Noradrenaline binding to β1  adrenergic receptor
Acetylcholine binding to muscarinic receptor
Prazosin binding to α1   adrenergic receptor
Phenoxybenzamine binding to alpha adrenergic receptor