Up to 1,600 jobs have been axed in the community pharmacy sector in the last nine months, research showed.
Union leaders blamed the staff reductions on cuts in payments to chemists under State drugs schemes, with an estimated 100,000 euro in lost earnings for every pharmacy.
The Irish Pharmacy Union (IPU) said around 300 pharmacists and 1,300 support staff had been let go as firms were forced to reduce opening hours and provide fewer services to patients.
Its survey found net profits fell by an average of 38% after Health Minister Mary Harney reduced payments to pharmacists last summer for medicines dispensed under community drugs schemes.
More than 70% of chemists had cut staff numbers and staff salaries while almost 90% reduced their own salary as owners of the pharmacy.
IPU vice-president Darragh O'Loughlin called on the minister to review her decision and warned services were set to suffer more in coming months.
"To date, pharmacists have borne the brunt of the cuts and have moved to reduce their overheads," he said.
"For pharmacies carrying any significant level of debt, where the net profit levels are below average for the sector, the consequences of the cuts are potentially devastating."
The research, undertaken by PriceWaterhouseCoopers on behalf of the IPU, also found 63% had been forced to stop providing screening services, 55% had to stop providing out-of-hours services, and 39% had been forced to reduce their opening hours.
Almost 20% had stopped providing free medicine delivery services to incapacitated patients and 23% were no longer providing medicine dosage monitoring for patients.