Meperidine belongs to the class of medications known as narcotic analgesics (pain relievers). It is used to treat moderate-to-severe pain associated with many medical, surgical, obstetrical, and dental procedures. It works to decrease pain by acting on the brain to increase pain tolerance. Meperidine works very quickly and will usually begin to relieve pain within 15 minutes. This medication should not be used to treat chronic pain.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

The usual adult dose of meperidine is 50 mg to 150 mg taken every 3 to 4 hours, as prescribed by the doctor and as necessary for pain.

The dose for seniors should be reduced to reduce the potential for adverse effects.

This medication may be habit-forming if taken for extended periods of time. It should not be used for longer than 2 days. Do not take this medication in higher doses or for a longer period of time than prescribed by your doctor.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you are taking this medication regularly, and you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Do not take meperidine if you:

• are allergic to meperidine or any ingredients of the medication
• are experiencing acute alcoholism or delirium tremens
• are experiencing acute asthma or other obstructive airway disease
• are experiencing acute respiratory depression
• have abnormal heart rhythms
• have a blockage of the gastrointestinal tract, particularly paralytic ileus
• have convulsive (seizure) disorders
• have cor pulmonale
• have head injury, brain tumour, or increased pressure inside the head or spinal cord
• have taken an MAO inhibitor within the past 14 days
• have severe depression of the central nervous system (i.e., sedation)
• have suspected abdominal conditions which may require surgery

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• blurred or double-vision or other changes in vision
• constipation
• dizziness, lightheadedness, or feeling faint
• drowsiness
• dry mouth
• false sense of well-being
• headache
• mood changes
• nausea
• stomach cramps or pain
• sweating
• weakness
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• fast, slow, or pounding heartbeat
• feelings of disassociation from reality
• hallucinations (hearing or seeing things that aren't there)
• hives, itching, or skin rash
• increased sweating
• irregular breathing
• redness or flushing of face
• shortness of breath, wheezing, or troubled breathing
• signs of urinary retention (e.g., decrease in amount of urine, difficulty urinating, frequent urge to urinate)
• swelling of face

Stop taking this medication and seek medical attention immediately if any of the following signs of overdose occur:

• signs of serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of shock (e.g., cold, damp skin; confusion; shakiness; nausea; weak, rapid pulse)
• signs of overdose
• cold, clammy skin
• confusion
• convulsions (seizures)
• dizziness (severe)
• drowsiness (severe)
• low blood pressure
• nervousness or restlessness (severe)
• "pinpoint" pupils of eyes
• slow heartbeat
• slow or troubled breathing
• weakness (severe)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Abdominal (stomach) conditions: Meperidine and other narcotic medications may make the diagnosis of abdominal conditions more difficult or it may worsen these conditions. If you have any abdominal problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Asthma and other respiratory conditions: Meperidine may cause increased breathing difficulty for people having an acute asthma attack, or those with chronic obstructive pulmonary disease (chronic bronchitis, emphysema) or other conditions that affect breathing. If you have asthma or other breathing disorders, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Dependence and withdrawal: As with other narcotics, this medication may become habit-forming if taken for long periods of time. Drug abuse is not a problem with people who require meperidine for pain relief. Physical dependence (a need to take regular doses to prevent physical symptoms) has been associated with narcotic analgesics. Withdrawal symptoms may occur if the medication is stopped suddenly. These symptoms include seizures, irritability, sleep problems, agitation, tremors, diarrhea, abdominal cramps, vomiting, headache, muscle cramps, extreme anxiety, tension, restlessness, sweating and confusion. If you have been taking meperidine for a prolonged time, you should stop the medication gradually if it is no longer required for pain control. Discuss the best way to stop this medication with your doctor.

Dizziness: Meperidine may cause dizziness when standing up from a sitting or lying position.

Drowsiness/reduced alertness: Meperidine may reduce the mental or physical abilities required to perform potentially hazardous tasks such as driving a car or operating machinery. Avoid these and other potentially hazardous tasks until you have determined how this medication affects you.

Head injuries: Meperidine can cause increased pressure inside the head. If you have an acute head injury or other conditions that increase intracranial pressure (pressure inside the head), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: If you have reduced liver function or liver disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Medical conditions: Meperidine may cause increased symptoms for people with hypothyroidism, Addison's disease, an enlarged prostate, or urethral strictures. If you have any of these conditions, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Seizures: Meperidine may worsen pre-existing seizure disorders. If tolerance to the medication develops and the dosage is increased substantially above recommended levels, seizures may occur in people without a history of seizure disorders. If you have a seizure disorder or a history of seizures, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: This medication crosses the placenta and may affect an unborn or newly born baby. Meperidine should not be used by pregnant women prior to being in labour unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking meperidine, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

There may be an interaction between meperidine and any of the following:

• alcohol
• amphetamines (e.g., dexamphetamine, lisdexamphetamine)
• anesthetics
• anticholinergic medications (e.g., benztropine, hyoscyamine)
• antihistamines that cause drowsiness (e.g., chlorpheniramine, dimenhydrinate, diphenhydramine, hydroxyzine)
• antipsychotic medications (e.g., chlorpromazine, haloperidol, quetiapine, risperidone)
• azelastine
• baclofen
• barbiturates (e.g., phenobarbital, thiopental)
• benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
• beta-blockers (e.g., atenolol, metoprolol, propranolol)
• buprenorphine
• buspirone
• butorphanol
• chloral hydrate
• cimetidine
• clonidine
• cyclobenzaprine
• darifenacin
• desmopressin
• dextromethorphan
• diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
• ergot alkaloids (e.g., dihydroergotamine, ergotamine)
• flavoxate
• ipratropium
• lithium
• MAO inhibitors (e.g., tranylcypromine, phenelzine) taken within the past 14 days
• methadone
• methocarbamol
• metoclopramide
• naltrexone
• other narcotic analgesics (e.g., codeine, fentanyl, morphine, oxymorphone)
• nefazodone
• orphenadrine
• paraldehyde
• pentazocine
• phenytoin
• pramipexole
• protease inhibitors (e.g., indinavir, lopinavir, ritonavir, saquinivir)
• rasagiline
• ropinirole
• scopolamine
• seizure medications (e.g., clobazam, ethosuximide, felbamate, levetiracetam, phenobarbital, phenytoin, primidone, topiramate, valproic acid, zonisamide)
• selective serotonin reuptake inhibitors (SSRIs; citalopram, fluoxetine, paroxetine)
• selegiline
• St. John's wort
• tiotropium
• tizanidine
• tolcapone
• tolterodine
• tramadol
• trazodone
• tricyclic antidepressants (e.g., amitriptyline, imipramine)
• "triptan" migraine medications (e.g., naratriptan, sumatriptan)
• tryptophan
• umeclidinium
• valerian
• venlafaxine
• zolpidem
• zopiclone

If you are taking any medications that have a sedating effect, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.