Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Nitrates or nitrites or nitric acid or nitrogen oxides
Patent
1995-10-31
1997-11-25
Jarvis, William R. A.
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Nitrates or nitrites or nitric acid or nitrogen oxides
514722, A61K 3300, A61K 3108
Patent
active
056909683
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB94/00839 filed Apr. 21, 1994.
The present invention relates to analgesic anaesthetic compositions, and particularly to such a composition comprising about 50% v/v nitrous oxide and oxygen, sold under the Registered Trade Mark `Entonox`.
The storage of gas mixtures in a homogenous state in a pressurized container is well established. It was shown in 1961 that a permanent gas, such as oxygen, was able to sustain nitrous oxide (a gas with analgesic and anaesthetic properties) in a homogenous gaseous admixture at temperatures and pressures at which previously part of the nitrous oxide was expected to separate out into liquid form (The Lancet 28 Oct. 1961, p 964) and in GB-A-967,930.
Following further studies, premixed nitrous oxide and oxygen at approximately 50/50 v/v mixture was made available. This was utilised for the relief of labour pains in child-birth from 1965 under the Trade Name `Entonox`. Entonox is inhaled for self-administered inhalation analgesia via a demand regulator under medical, nursing or paramedical supervision for many applications in addition to child-birth. The fundamental advantages of premixing the gases in a single pressurized container are safety (the oxygen supply cannot fail), and simplicity (no mixing device is required).
Nitrous oxide at 50% is itself a potent analgesic agent, which after more than a minute or so of deep and rapid inhalations causes a number of patients to become amnesic, inaccessible to instructions and uncontrollable in response to strong stimuli. Its uptake and excretion are both rapid. It is because the pain of each uterine contraction of child-birth is both of such relatively short duration and is separated by a few minutes from the next pain that 50% nitrous oxide has been practical for use as an analgesic. Each episode of inhalations during child-birth is normally too short to allow amnesic levels of nitrous oxide to be reached in the brain. Nitrous oxide at a concentration of 50% is generally the lowest concentration used for women in labour and will make a number of people unresponsive if breathed for long enough. Nitrous oxide at a concentration of 30% has been used in dentistry for more prolonged times. This is probably the lowest concentration that is used.
The rapid uptake and excretion of nitrous oxide requires special understanding by those supervising the use of Entonox. For constant pain, say during ambulance transport following injury, the patient needs to be instructed in the correct intermittent use of Entonox to make the most of its advantages. When Entonox is administered for short painful procedures not requiring a general anaesthetic, such as the withdrawal of drainage tubes and certain other therapeutic procedures, it is always a problem to attain the correct timing and duration of inhalation to cover the peak of pain.
These problems suggest that an inhalation admixture with a lower concentration of nitrous oxide, but with the addition of a volatile ether-based analgesic agent such as isoflurane, would allow a longer duration of inhalation, better maintenance of co-operation and more prolonged pain relief. Such mixtures, with their slower onset and decline of analgesia, have already been shown to be beneficial.
Gas mixtures containing nitrous oxide and oxygen were covered in GB-A-967930 (1961). Included in that disclosure was the use of the volatile anaesthetic agent Halothane at up to 1% as an adjuvant to the admixture. Halothane is a volatile non-analgesic anaesthetic agent which however has been shown to be unstable in the presence of light, oxygen and metal (see British Journal of Anaesthesia, 1984, Volume 56, Supplement 3s to 7s; R. C. Terrell).
It has recently been shown that the inhalation of Entonox, with the separate addition of 0.25% isoflurane vapour, provides more relief for the pains of childbirth than Entonox alone (International Journal of Obstetric Anaesthesia 1992, Vol 1 p199-202). Isoflurane is a volatile ether-based analgesic anaesthetic agent. In this disclosure, isoflurane was adde
REFERENCES:
S. Arora et al. "Self-administered mixture of entonox and isoflurane in labour" International Journal of Obstetric Anaesthesis, vol. 1, 1992, pp. 199-202.
Rodgers Robert Colin
Ross John Alexander Strachan
Tunstall Michael Eric
Aberdeen University
Jarvis William R. A.
LandOfFree
Analgesic anaesthetic compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Analgesic anaesthetic compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Analgesic anaesthetic compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2104625