Pharmacists have warned that medicine shortages are causing "extreme distress" to patients and in some cases even causing admittance to hospital.
Nearly a third of 150 community pharmacies questioned revealed patients had suffered because they had difficulty getting medicines including those for breast cancer, blood clots as well as antidepressants.
One patient suffered panic attacks waiting for the antidepressant Cipralex, while another said the delay in receiving the breast cancer drug Femara had caused "extreme distress", pharmacists reported.
Meanwhile a shortage of the blood clot drug Plavix contributed to the hospital admission of another patient.
Nearly 90% of respondents to the Chemist & Druggist survey said they were "very concerned" about problems they were having getting hold of some medicines.
Roger Odd, a trustee of the Patients' Association, said: "There are 50 or more medicines that have been out of stock, it's unbelievable. It can't be right for patients to be suffering like this."
The supply problems are being blamed on a production quotas set by drug manufacturers and a healthy export market for medicines.
A spokesman for the Department of Health said officials were aware of the issue.