The increase was primarily due to product costs associated with higher sales volumes of our devices and increased overhead stemming from our move into our new manufacturing facility during early 2023. Sales and marketing expenses totaled $3.4 million for the fourth quarter ended December 31, 2023. This reflects a modest increase compared to the quarter ended September 2023 and an increase of $1 million or 40% to the quarter ended December 2022. Sales and marketing expenses for the full-year 2023 increased to $13.1 million, an increase of $4.2 million or 48% compared to the year ended December 31, 2022. Although expenses for the current quarter reflect increases relative to prior periods during the second half of 2023, we reduced our sales expense rate from $3.6 million for the second quarter to $3.4 million for the fourth quarter just completed.
This 6% reduction was achieved while driving two additional sequential quarters of top line growth over 13%. General and administrative expenses totaled $4 million for the fourth quarter ended December 31, 2023. This reflects an increase of $0.5 million or 16% compared to the quarter ended September 2023 and a decrease of $1.7 million or 30% compared to the quarter ended December 2022 respectively. For the full-year 2023, general and administrative expenses increased to $15.2 million, an increase of $5.3 million or 54% compared to $9.9 million for the year ended December 31, 2022. Within G&A, certain expenses reflect costs that scale with top line and production growth, such as credit card fees, but those are not the key drivers of incremental expenses versus prior year.
Q4 was another active quarter for us as a public company as we completed filing of our S-1 registration statement and proxy statement and held a special shareholder meeting stemming from our Series A preferred stock financing. In addition, a trailing obligation of the 2022 leaseback was the commitment to make our senior and subordinated indentures tradable through the depository trust company. Any one of these activities would be a solid accomplishment during the quarter. We accomplished all three while also closing the final tranche of our Series A financing and maintaining ongoing operations. To achieve this, we leveraged outside counsel and required the involvement of our current and predecessor audit firms. Our professional fees as a result ran higher than what we expensed during the third quarter of 2023.
With that said, turning back to the second quarter when we began our cost reductions, G&A finished the fourth quarter, 11% lower than the second quarter of 2023. Research and development expenses increased to $1.4 million for the quarter ended December 31, 2023. This reflects an increase of $300,000 or 16% and $300,000 or 28% compared to the quarters ended September 2023 and December 2022, respectively. For the full-year 2023, research and development expenses increased to $4.8 million, an increase of $1.8 million or 61% compared to the year ended December 31, 2022. This increase was primarily driven by an increase in expenses associated with the ongoing development of the RPMO2, the frontline OSA therapy study, FLOSAT and costs associated with preparing the 510(k) premarket notification to the FDA for the severe indication label expansion.
Other income and expense continues to be dominated by accounting fair value charges and noncash debt restructuring charges. Interest expense remains consistent, reflecting the interest expense associated with our senior and subordinate indentures accompanied by equipment financing interest. As our stock price fluctuates, our fair values will also fluctuate accordingly. Turning now to the balance sheet. Cash, restricted cash and cash equivalents totaled $7.1 million compared to $12 million for the third quarter of 2023. During the fourth quarter, we reclassified a $700,000 CD opened earlier in 2023 relating to our headquarters facility lease as restricted cash to reflect the limitations of its use for general purposes. The $4.9 million reduction of cash during the fourth quarter reflects $3.9 million used in ongoing operations accompanied by a $1 million outlay to renew our annual insurance.
This insurance expense will be amortized ratably over the next 12 months. As we’ve discussed on prior calls, we are aware of our capital requirements and the impacts of the current capitalization of the company on value realization. As such, we are reviewing and considering financing and strategic alternatives focusing on our ability to make ProSomnus precision appliances available to patients with OSA and the health professionals overseeing their care. This is a comprehensive process and while we are optimistic based on our current standing and progress made so far, nothing is done until it is formally done. We plan to disclose further developments as required by applicable law or regulation as applicable. Next, we are working closely with NASDAQ to regain minimum listing requirements.