Doctor shopping
The concept of doctor shopping relates to a patient's addiction or reliance on a certain prescription drug or other medical treatment.  Usually a patient will be treated by their normal physician and be prescribed a drug that is necessary for the legitimate treatment of their current medical condition.  Once that condition has been successfully treated however, most conscientious physicians will not continue to provide their patients with the medications that they were taking.  These patients will now actively seek out other physicians to obtain more of the same medication, often by faking or exaggerating the extent of their true condition, in order to feed their addiction to that drug.  Some patients have been known to go so far as to break or chip teeth and visit emergency rooms complaining of toothaches to receive prescription painkillers.
It should be noted however that not all patients seeking inappropriate multiple prescriptions of drugs are doing so because of addiction or an intention to abuse the drugs for their recreational effects. Increasing scrutiny of prescribing practices and high-profile prosecutions of doctors for allegedly over-prescribing drugs such as opiate painkillers and benzodiazepine tranquilizers has made many doctors extremely reluctant to prescribe large doses or repeat prescriptions of these drugs, even to patients with a legitimate medical need.  Some consider the high-profile case of Richard Paey an example of such.

# Reasons for prescription-only drugs
There are certain drugs that pharmacies cannot provide to the general public unless the client has prescription for that drug. This restriction is generally in place because at least one of the following is true:
- The drug can have severe side-effects
- The drug should not be taken over a prolonged period of time
- If combined with other drugs or alcohol, the use of the medication could have unsafe or deadly consequences
- The use of the drug needs to be supervised under a doctor's care
- The drug has a legitimate, accepted medical use, but has the potential for dependency or abuse.

# Commonly abused prescription drugs
In the context of doctor shopping, the three most common conditions that are treated are insomnia, anxiety or pain.
Most sleeping pills and other sedatives cannot be obtained without a prescription, because they have a high potential for dependence. If sedatives are prescribed, they are usually dispensed in small quantities, which will last one week or even less.  Examples of such drugs include zolpidem (Ambien), alprazolam (Xanax), and diazepam (Valium).  Dependence on such medications usually arises because the patient, for psychological or other reasons, comes to rely on the effects of the drug to fall asleep, or to prevent anxiety attacks.
Many prescription pain medications contain an opioid painkiller and a number of these have a high potential for addiction and abuse, including oxycodone (common brand names Percocet, OxyContin), meperidine (brand name Demerol), hydromorphone (Palladone, Dilaudid), and morphine (MS Contin, Kadian, Avinza). Even the milder opioids (such as codeine, tramadol, and hydrocodone), while generally less addictive, can still be problematic. Newer medications of abuse include various preparations of the extremely potent and addictive narcotic analgesic fentanyl, including Duragesic (a self-adhesive skin patch, available in four strengths) and Actiq (berry-flavored lollipops that the user sucks, available in six strengths). All of these are categorized as Schedule II drugs under the U.S. Controlled Substances Act (with the exception of tramadol and some preparations of codeine, morphine, and hydrocodone) and have stringent physical security associated with them. They must remain under lock and key at all times; every tablet must be precisely accounted for; no refills are permitted on prescriptions; and no telephone orders are accepted, with the exception of pallative care facilities (e.g., to discourage prescription fraud).

# Legal issues
Because of the widespread abuse of prescription drugs in both the United States and around the world, regulatory authorities have been cracking down on the process of doctor shopping, with some U.S. states even criminalizing the practice.  Doctors have also undergone both education and training in recent years about the dangers of prescribing unneeded medication (it casts a bad light on the doctor, and often public health systems pay for prescribed medication, so it will cost the taxpayer more).