Penthrox inhaler
Encyclopedia
The Penthrox inhaler, manufactured and marketed by Medical Developments International (Melbourne
, Victoria
, Australia
), is a hand-held inhaler
device which can be used for the self-administration
of methoxyflurane
for analgesia
(relief of pain).
alternative to morphine
, this device is also easier to use than nitrous oxide
.
) toxicity
, methoxyflurane is contraindicated
in patients with pre-existing kidney disease
or diabetes mellitus
, and is not recommended to be administered in conjunction with tetracyclines or other potentially nephrotoxic or enzyme-inducing
drugs.
stable patients (including children over the age of 5 years) to self-administer the drug, under supervision. Each 3 milliliter dose lasts approximately 30 min.
s have been reported in the literature when it is used at the lower doses (up to 6 millileters) used for producing analgesia and sedation
.
St John Ambulance Australia
(SJAA) offers certification for paramedics
to administer the drug in remote settings. As of 2010, methoxyflurane was listed under the Australian Pharmaceutical Benefits Scheme
for the initial management of pain due to acute trauma
, as well as for brief painful procedures such as changing of wound dressings or for patient transport.
and New Zealand
Defence Forces, and the Australian ambulance services
.
In 1968, Robert Wexler of Abbott Laboratories
developed the Analgizer, a disposable inhaler that allowed the self-administration of methoxyflurane vapor
in air for analgesia. The Analgizer consisted of a polyethylene
cylinder 5 inches in length and 1 inch in diameter with a 1 inch long mouthpiece. The device contained a rolled wick
of polypropylene
felt
which held 15 milliliters of methoxyflurane. Because of the simplicity of the Analgizer and the pharmacological
characteristics of methoxyflurane, it was easy for patients to self-administer the drug and rapidly achieve a level of conscious analgesia which could be maintained and adjusted as necessary over a period of time lasting from a few minutes to several hours. The 15 milliliter supply of methoxyflurane would typically last for two to three hours, during which time the user would often be partly amnesic
to the sense of pain; the device could be refilled if necessary. The Analgizer was found to be safe, effective, and simple to administer in obstetric
patients during childbirth, as well as for patients with bone fracture
s and joint dislocations, and for dressing changes on burn
patients. When used for labor analgesia, the Analgizer allows labor to progress normally and with no apparent adverse effect on Apgar score
s. All vital signs
remain normal in obstetric patients, newborns, and injured patients. The Analgizer was widely utilized for analgesia and sedation until the early 1970s, in a manner that foreshadowed the patient-controlled analgesia
infusion pump
s of today. The Analgizer inhaler was withdrawn in 1974, but use of methoxyflurane as a sedative and analgesic continues in Australia and New Zealand in the form of the Penthrox inhaler.
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
, Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
), is a hand-held inhaler
Inhaler
An inhaler or puffer is a medical device used for delivering medication into the body via the lungs. It is mainly used in the treatment of asthma and Chronic Obstructive Pulmonary Disease . Zanamivir , used to treat influenza, must be administered via inhaler...
device which can be used for the self-administration
Patient-controlled analgesia
Patient-controlled analgesia is any method of allowing a person in pain to administer their own pain relief. The infusion is programmable by the prescriber...
of methoxyflurane
Methoxyflurane
Methoxyflurane is a halogenated ether that was in clinical use as an volatile inhalational anesthetic from its introduction by Joseph F. Artusio et al in 1960 until around 1974. It was first synthesized in the late 1940s by William T...
for analgesia
Analgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....
(relief of pain).
Indications
The Penthrox inhaler is indicated for use by children and adults for the self-administration of methoxyflurane for analgesia in emergency and remote settings. A non-opioidOpioid
An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...
alternative to morphine
Morphine
Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
, this device is also easier to use than nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
.
Contraindications
Due to the risk of organ (especially kidneyKidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
) toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
, methoxyflurane is contraindicated
Contraindication
In medicine, a contraindication is a condition or factor that serves as a reason to withhold a certain medical treatment.Some contraindications are absolute, meaning that there are no reasonable circumstances for undertaking a course of action...
in patients with pre-existing kidney disease
Nephropathy
Nephropathy refers to damage to or disease of the kidney. An older term for this is nephrosis.-Causes:Causes of nephropathy include administration of analgesics, xanthine oxidase deficiency, and long-term exposure to lead or its salts...
or diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, and is not recommended to be administered in conjunction with tetracyclines or other potentially nephrotoxic or enzyme-inducing
Enzyme inducer
An enzyme inducer is a type of drug which binds to an enzyme and increases its metabolic activity.Classic examples: barbiturates , antiepileptics and rifampin....
drugs.
Dosing
The maximum recommended dose is 6 milliliters per day or 15 millileters per week because of the risk of cumulative dose-related nephrotoxicity, and the inhaler should not be used on consecutive days.How supplied
This portable, disposable, single-use inhaler device, along with a single 3 milliliter brown glass vial of methoxyflurane is provided in doctor's kits that allows conscious hemodynamicallyHemodynamics
Hemodynamics, meaning literally "blood movement" is the study of blood flow or the circulation.All animal cells require oxygen for the conversion of carbohydrates, fats and proteins into carbon dioxide , water and energy in a process known as aerobic respiration...
stable patients (including children over the age of 5 years) to self-administer the drug, under supervision. Each 3 milliliter dose lasts approximately 30 min.
Adverse effects
Despite the potential for renal impairment when used at anesthetic doses, no significant adverse effectAdverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
s have been reported in the literature when it is used at the lower doses (up to 6 millileters) used for producing analgesia and sedation
Sedation
Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure...
.
St John Ambulance Australia
St John Ambulance Australia
St John Ambulance Australia is a self-funding charitable organisation dedicated to helping people in sickness, distress, suffering or danger. It is part of an international organisation that consists of eight Priories that form the Order of St John.- History :St John First Aid training centres...
(SJAA) offers certification for paramedics
Paramedics in Australia
A paramedic in Australia is a health care professional who responds to and treats all types of medical and trauma emergencies outside of a hospital setting before and during transportation to an appropriate medical facility...
to administer the drug in remote settings. As of 2010, methoxyflurane was listed under the Australian Pharmaceutical Benefits Scheme
Pharmaceutical Benefits Scheme
The Pharmaceutical Benefits Scheme or PBS is a program of the Australian Government that provides subsidised prescription drugs to residents of Australia. The PBS ensures that all Australians have affordable and reliable access to a wide range of necessary medicines.-History:The PBS was established...
for the initial management of pain due to acute trauma
Trauma (medicine)
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
, as well as for brief painful procedures such as changing of wound dressings or for patient transport.
History
Methoxyflurane has been extensively used since the 1970s in Australia as an emergency analgesic for short-term use, mostly by the AustralianAustralian Defence Force
The Australian Defence Force is the military organisation responsible for the defence of Australia. It consists of the Royal Australian Navy , Australian Army, Royal Australian Air Force and a number of 'tri-service' units...
and New Zealand
New Zealand Defence Force
The New Zealand Defence Force consists of three services: the Royal New Zealand Navy; the New Zealand Army; and the Royal New Zealand Air Force. The Commander-in-Chief of the NZDF is His Excellency Rt. Hon...
Defence Forces, and the Australian ambulance services
Emergency medical services in Australia
Emergency medical services in Australia are provided by state ambulance services, which are a division of each state or territorial government, and by St John Ambulance in both Western Australia and the Northern Territory.-Land Ambulance:...
.
In 1968, Robert Wexler of Abbott Laboratories
Abbott Laboratories
Abbott Laboratories is an American-based global, diversified pharmaceuticals and health care products company. It has 90,000 employees and operates in over 130 countries. The company headquarters are in Abbott Park, North Chicago, Illinois. The company was founded by Chicago physician, Dr....
developed the Analgizer, a disposable inhaler that allowed the self-administration of methoxyflurane vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....
in air for analgesia. The Analgizer consisted of a polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
cylinder 5 inches in length and 1 inch in diameter with a 1 inch long mouthpiece. The device contained a rolled wick
Candle wick
A candle wick is a string, cord, or wooden object that holds the flame of a candle. A candle wick works by capillary action, drawing the fuel to the flame. When the liquid fuel, typically melted candle wax, reaches the flame it then vaporizes and combusts. The candle wick influences how the...
of polypropylene
Polypropylene
Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...
felt
Felt
Felt is a non-woven cloth that is produced by matting, condensing and pressing woollen fibres. While some types of felt are very soft, some are tough enough to form construction materials. Felt can be of any colour, and made into any shape or size....
which held 15 milliliters of methoxyflurane. Because of the simplicity of the Analgizer and the pharmacological
Pharmacology
Pharmacology is the branch of medicine and biology concerned with the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function...
characteristics of methoxyflurane, it was easy for patients to self-administer the drug and rapidly achieve a level of conscious analgesia which could be maintained and adjusted as necessary over a period of time lasting from a few minutes to several hours. The 15 milliliter supply of methoxyflurane would typically last for two to three hours, during which time the user would often be partly amnesic
Amnesia
Amnesia is a condition in which one's memory is lost. The causes of amnesia have traditionally been divided into categories. Memory appears to be stored in several parts of the limbic system of the brain, and any condition that interferes with the function of this system can cause amnesia...
to the sense of pain; the device could be refilled if necessary. The Analgizer was found to be safe, effective, and simple to administer in obstetric
Obstetrics
Obstetrics is the medical specialty dealing with the care of all women's reproductive tracts and their children during pregnancy , childbirth and the postnatal period...
patients during childbirth, as well as for patients with bone fracture
Bone fracture
A bone fracture is a medical condition in which there is a break in the continuity of the bone...
s and joint dislocations, and for dressing changes on burn
Burn
A burn is an injury to flesh caused by heat, electricity, chemicals, light, radiation, or friction.Burn may also refer to:*Combustion*Burn , type of watercourses so named in Scotland and north-eastern England...
patients. When used for labor analgesia, the Analgizer allows labor to progress normally and with no apparent adverse effect on Apgar score
Apgar score
The Apgar score was devised in 1952 by the eponymous Dr. Virginia Apgar as a simple and repeatable method to quickly and summarily assess the health of newborn children immediately after birth...
s. All vital signs
Vital signs
Vital signs are measures of various physiological statistics, often taken by health professionals, in order to assess the most basic body functions. Vital signs are an essential part of a case presentation. The act of taking vital signs normally entails recording body temperature, pulse rate ,...
remain normal in obstetric patients, newborns, and injured patients. The Analgizer was widely utilized for analgesia and sedation until the early 1970s, in a manner that foreshadowed the patient-controlled analgesia
Patient-controlled analgesia
Patient-controlled analgesia is any method of allowing a person in pain to administer their own pain relief. The infusion is programmable by the prescriber...
infusion pump
Infusion pump
An infusion pump infuses fluids, medication or nutrients into a patient's circulatory system. It is generally used intravenously, although subcutaneous, arterial and epidural infusions are occasionally used....
s of today. The Analgizer inhaler was withdrawn in 1974, but use of methoxyflurane as a sedative and analgesic continues in Australia and New Zealand in the form of the Penthrox inhaler.