By the time propranolol was launched, ICI was beginning to experience competition from other companies. This potential threat led to ongoing refinements in the pharmacologic structure of β-blockers and subsequent advances in drug delivery. ICI studied analogues further and in 1970 launched practolol (figure 4) under the trade name Eraldin. It was withdrawn from the market a few years later because of the severe side effects it caused, nevertheless it played a large role in the fundamental study of β-blockade and β-receptors.
The withdrawal of Eraldin gave ICI the nudge to launch another β-blocker, atenolol, which was launched in 1976 under the trade name Tenormin. Atenolol is a selective β1-receptor antagonist and was developed for the purpose of obtaining the “ideal β-blocker”.  It soon became one of the best-selling heart drug. ICIs β-blocker project was based on Ahlquists dual receptor theory. The drugs that were the outcome of this project, from propranolol to atenolol, helped to establish the receptor theory among scientist and pharmaceutical companies.
The progress in β-blocker development led to the introduction of drugs with variety of properties. β-blockers were developed having a relative selectivity for cardiac β1-receptors (for example metoprolol and atenolol), partial adrenergic agonist activity (pindolol), concomitant α-adrenergic blocking activity (for example labetalol and carvedilol) and additional direct vasodilator activity (nebivolol). In addition, long-acting and ultra-short formulations of β-blockers were developed. In 1988, Sir James Black was awarded the Nobel Prize in Medicine for his work on drug development.