Physician Assistants (PAs) are highly trained, nationally certified, and state-licensed medical professionals who practice medicine in collaboration with physicians and other members of the healthcare team. PAs are educated in a broad, generalist medical model and are authorized to diagnose illness, develop treatment plans, interpret tests, and prescribe medication across various specialties. However, the scope of a PA’s practice is defined by clear legal, administrative, and clinical boundaries that differ significantly from those of a physician. Understanding these limitations clarifies the professional structure within which PAs operate.
The Foundational Constraint: Required Supervision and Collaboration
PAs cannot practice medicine independently in the same manner as a physician (MD or DO) and must operate under a formal relationship with a collaborating physician. This relationship is a structural mandate governed by state law and medical board regulations. The physician retains ultimate responsibility for the medical services provided by the PA, even if they are not physically present.
State practice acts detail the specific nature of this oversight, often outlining requirements such as the maximum number of PAs a physician can collaborate with or the percentage of patient charts requiring a physician’s co-signature. While many states are modernizing their laws toward “Optimal Team Practice” (OTP), which removes the legal requirement for a specific physician-PA relationship, a collaborative structure remains mandatory. This team-based approach ensures continuous direction and oversight of the PA’s work, even when the physician is not on-site.
Limitations on Legal and Administrative Documentation
PAs face restrictions regarding the signing of specific legal and administrative documents that carry ultimate clinical or legal authority. Documents such as death certificates, which legally certify the cause and time of death, typically require a physician’s signature. This limitation is rooted in state statutes that assign final certification authority exclusively to physicians, medical examiners, or coroners.
Similar restrictions apply to certain workers’ compensation forms or papers related to involuntary commitment, where a physician’s primary signature or countersignature is often a regulatory requirement. Beyond clinical documentation, PAs are generally limited in their ability to legally form and operate independent medical corporations or Professional Corporations (P.C.s) in most jurisdictions. This is often due to the Corporate Practice of Medicine (CPOM) doctrine, which restricts non-physicians from owning entities that practice medicine, aiming to ensure that clinical decisions are not influenced by corporate interests. In many states, if a PA has an ownership stake, it is often limited to a minority share, requiring a licensed physician to maintain majority ownership and ultimate control over medical operations.
Restrictions on Primary Surgical Roles
While PAs are often highly skilled members of surgical teams, they cannot serve as the primary operating surgeon responsible for the overall outcome of the procedure. The primary operating surgeon holds the personal and non-delegable responsibility for the patient’s welfare throughout the entire operation. This responsibility is legally and ethically assigned to the attending physician who possesses the full scope of license for that procedure.
A PA’s role in the operating room is defined as supportive and assistive, frequently serving as the first assistant. PAs perform complex tasks, such as harvesting veins for bypass surgery, closing surgical wounds, and performing certain procedures under local anesthesia. Institutional bylaws and hospital credentialing committees explicitly define the PA’s privileges, ensuring the PA’s involvement is always within the context of assisting the primary surgeon. Even when performing a procedure, the PA is acting under the direction of the attending surgeon.
Constraints on Prescribing Controlled Substances
PAs possess broad authority to prescribe medications, but they face specific limitations concerning controlled substances, which are regulated by both federal and state laws. The federal Drug Enforcement Administration (DEA) requires PAs to obtain their own registration number to prescribe controlled substances, rather than using the collaborating physician’s number. State laws often impose additional limitations based on the substance’s schedule.
Constraints are most frequently applied to Schedule II controlled substances, which have the highest abuse potential among accepted medical drugs. Many states impose mandatory limits on the quantity or duration of the prescription, such as an initial 72-hour supply for acute pain. Longer-term prescriptions often require explicit authorization from the collaborating physician. PAs are universally prohibited from prescribing Schedule I drugs, which are classified as having a high potential for abuse and no currently accepted medical use.
Inability to Practice Outside Defined Scope of Competency
A PA cannot simply choose to practice in any specialty or perform any procedure, even if supervision is technically available. The PA’s clinical scope is defined by a combination of their education, documented experience, the practice setting’s policies, and the scope of practice of their collaborating physician. This framework ensures the PA remains within their professional capabilities.
The practice agreement between the PA and the physician dictates the specific tasks and procedures the PA is authorized to perform. For instance, a PA who has spent their career in dermatology cannot abruptly begin performing cardiac surgery, as this falls outside their established competence. Licensed healthcare facilities enforce this limitation by requiring PAs to apply for specific clinical privileges, which are only granted after verifying professional credentials and competency in those distinct areas.
Differences in Professional Liability and Practice Ownership
PAs are typically employees within a medical facility or practice, creating a distinct structure for professional liability compared to physicians. The legal doctrine of vicarious liability often applies, meaning the physician or the medical entity employing the PA can be held legally responsible for the PA’s negligence if it occurs during job-related duties. This structure means the PA is not the ultimate financial or legal bearer of responsibility in many malpractice cases.
The physician, as the ultimate authority, carries the final legal and financial responsibility for the patient’s care, a burden that cannot be delegated. This difference in liability structure also restricts the PA’s role in business governance and decision-making within the practice. PAs generally cannot serve as the final decision-maker regarding practice standards or personnel matters, because the ultimate clinical and legal authority rests with the physician or the physician-led corporate entity.