A prescription medication is a licensed medicine that is regulated by legislation to require a prescription before it can be obtained. The term is used to distinguish it from over-the-counter drugs which can be obtained without a prescription. Different jurisdictions have different definitions of what constitutes a prescription drug.
Dispensation of prescription drugs often includes a monograph (in Europe, a Patient Information Leaflet or PIL) that gives detailed information about the drug.
 Regulation in United States
In the United States, the Federal Food, Drug, and Cosmetic Act defines what requires a prescription. Prescription drugs are generally authorized by veterinarians, dentists, optometrists, and medical practitioners. It is generally required that an MD, DO, PA, OD, DPM, DVM, DDS, or DMD write the prescription; basic-level registered nurses, medical assistants, clinical nurse specialists, nurse anesthetists, and nurse midwives, emergency medical technicians, psychologists, and social workers as examples, do not have the authority to prescribe drugs.
The package insert for a prescription drug contains information about the intended effect of the drug and how it works in the body. It also contains information about side effects, how a patient should take the drug, and cautions for its use, including warnings about allergies.
The safety and effectiveness of prescription drugs in the US is regulated by the federal Prescription Drug Marketing Act of 1987. The Food and Drug Administration (FDA) is charged with implementing this law.
As a general rule, over-the-counter drugs (OTC) are used to treat conditions not necessarily requiring care from a health care professional and have been proven to meet higher safety standards for self-medication by patients. Often a lower strength of a drug will be approved for OTC use, while higher strengths require a prescription to be obtained; a notable case is ibuprofen, which has been widely available as an OTC pain killer since the mid-1980s but is still available by prescription in doses up to four times the OTC dose for use in cases of severe pain not adequately controlled by the lower, OTC strength.
Herbal preparations, vitamins, minerals, and food supplements are not regulated by the FDA, so the individual consumer must be aware of the potential negative effects of using these preparations and also the potential interactions with prescription drugs they may be taking.
In the United States, the term "prescription drug" is most commonly used, but they are also called Rx-only drugs or legend drugs, after the Federal and State laws which mandate that all such drugs bear a "legend" prohibiting sale without a prescription; though more complex legends have been used, on most original drug packaging today the legend simply says "Rx only".
Also, pharmacies operated by membership clubs, such as Costco and Sam's Club, by law must allow non-members to use their pharmacy services and must charge the same prices as to members.
Physicians may legally prescribe drugs for uses other than those specified in the FDA approval; this is known as off-label use. Drug companies may not promote or market drugs for off-label uses.
Large U.S. retailers that operate pharmacies and pharmacy chains use inexpensive generic drugs as a way to attract customers into stores. Several chains, including Walmart, Target, and others, offer $4 monthly prescriptions on select generic drugs as a customer draw.
 Regulation in United Kingdom
In the United Kingdom the Medicines Act 1968 governs the manufacture and supply of three categories of medicine:
- Prescription only medicines (POM) which can be sold by a pharmacist if prescribed by a doctor
- Pharmacy medicines (P) which may be sold by a pharmacist without prescription
- General sales list (GSL) medicines which may be sold without a prescription in any shop
Possession of prescription only medicines without a prescription is a criminal offence.
A patient visits a medical practitioner who is able to prescribe medication. District nurses and health visitors have had limited prescribing rights since the mid-nineties where prescriptions for dressings and simple medicines would have had to have been signed by a medical practitioner.
If given an NHS prescription, this can be taken to a pharmacy to be dispensed, for which a per-item charge is payable. This charge is paid entirely to the NHS through the pharmacy, while the pharmacy claims the cost of the medicine dispensed.
Each item can cover any prescribed item in a very large or very small quantity according to the prescription. This means that the patients perceived value of the charge can vary enormously - the actual cost of the medicine given out may vary from a few pence to hundreds of pounds. However, medical practitioners can prescribe a maximum three month supply of the medication in order for it to be covered under the NHS. If a medical practitioner wishes to prescribe a supply in excess of three months, the prescriber must write a separate, private prescription for the balance of the medication supply in excess of three months for which the patient must pay the actual price as charged by the pharmacist. Certain groups of patients are exempt from this charge, such as those over 60, under 16 (or under 19 if in full-time education), patients with certain medical conditions, those on certain benefits and those with an HC2 certificate, which is issued if a patient can prove their income is under –8,000 per year. Prescription fees are currently –7.20 per item in England. However, in Wales prescription charges have been abolished and in Scotland prescription charges have reduced each year from 1 April 2008, currently standing at –3 per item (from 1 April 2010). They will be abolished completely on 1 April 2011.
An HC2 certificate can be applied for by those on a low income or in receipt of Incapacity Benefit. Claimants of Income Based Jobseeker's Allowance, Income Support and Employment and Support Allowance automatically receive free prescriptions.
Those requiring regular prescriptions may make a saving by purchasing a pre-payment certificate which covers the cost of all prescriptions required for three months or a year. In 2010, these were –104 for 12 months, or –28.25 for 3 months.
Many of the prescriptions dispensed on NHS are exempt from charges. This is because of the large number of prescription medicines needed by, for example, the elderly or those with medical exemptions. NHS prescriptions can also be written for certain medical items. Some patients also receive private prescriptions, typically either from a medical practitioner seen privately or for medicines not covered on the NHS. For these, the patient will pay the pharmacy directly for the cost of the medicine and the pharmacy's dispensing fee.
 Expiration date
The expiration date, required in several countries, specifies the date the manufacturer guarantees the full potency and safety of a drug. Most medications are potent and safe after the expiration date. A study conducted by the U.S. Food and Drug Administration covered over 100 drugs, prescription and over-the-counter. The results showed that about 85% of them were safe and effective as far as 15 years past their expiration date. Joel Davis, a former FDA expiration-date compliance chief, said that with a handful of exceptions - notably nitroglycerin, insulin and some liquid antibiotics - most expired drugs are probably effective. The American Medical Association (AMA) issued a report and statement on Pharmaceutical Expiration Dates.
 Environmental problems
Traces of prescription drugs'including antibiotics, anti-convulsants, mood stabilizers and sex hormones'have been detected in drinking water. If ingested these may be harmful to wildlife and humans.
 See also
 Further reading