described here are metered dose inhalers of the invention that generally include a primeless valve and a minimal volume pressurized canister . the combination of a primeless , i . e ., non - retention valve , with a canister designed to provide the minimum volume around a valve to avoid unnecessary overfilling of drug formulation , drug loss to excessive surface areas of larger canisters and drug loss to priming shots is described . as previously mentioned , priming actuations are typically required and are fired to the environment with conventional valves , resulting in uncontrolled and unnecessary drug exposure and waste . by having a primeless valve , no priming is required and the first actuation of the canister / valve combination delivers a full dose . in some variations , reduced priming ( in comparison to conventional valves ) is employed . in one variation of the invention , the primeless valve is capable of metering from 10 microliters to 200 microliters without recent previous priming , even after extended storage between usage , ranging from 1 day to about 2 years . the canister can be of diameters varying from about 8 millimeters to about 30 millimeters with heights varying between about 10 millimeters to about 30 millimeters . the canister may be formed from glass , plastic , metal , or combinations thereof , and coated or uncoated as appropriate for the formulation . an exemplary primeless valve and minimal volume canister assembly 100 of the invention is depicted in fig1 . assembly 100 is made up of canister 140 , cap 120 and valve 110 . note that length of body wall 130 of the canister 140 may be further reduced to decrease the internal volume of canister 140 and minimize the required ullage ullage is a term known to those skilled in the art and represents the minimum residual volume level from which the metering chamber of the valve can effectively be filled with drug formulation . if there is less than this ullage ( minimum volume ), erratic dose metering from the valve may be experienced and consistent delivery may be no longer possible . in one variation , valve 110 is configured to deliver a unit dose of active agent upon the first and any subsequent actuation of the valve stem the minimal volume canisters of the invention may be of any dimension and geometry . they are configured to minimize the amount of the active agent within the canister in order to avoid potential toxicity , overdose , or abuse of the agent contained therein . the volume of the canister is reduced by reducing the dimensions of the canister itself , not by placing an insert or second canister within it . the canister may be used with any suitable inhaler . the containers described here generally include a pressurized canister , a valve fixedly attached to the proximal end of the canister , and a metering chamber . the pressurized canister may hold any active agent . for example , the active agent may be a central nervous system ( cns ) agent such as ondansetron , granisetron , ropinirole , sildenafil , a benzodiazepine , a barbiturate , an ergot alkyloid , such as dihydroergotamine , a narcotic analgesic such as an opioid , including fentanyl , morphine , hydromorphone , oxycodone , or a metabolic replacement or modulation agent , such as pth , insulin , glp - 1 , ppt , exenatide , or neuropeptides such as pyy . combinations , salts , analogs , and derivative of the aforementioned active agents are also contemplated . typical cns therapies would require only about 2 to about 10 actuations to provide a single treatment . examples could include fentanyl or other opiates , for breakthrough pain , dihydroergotamine or sumatriptan for migraine treatment , or copaxone ® for ms treatment , sedatives for insomnia , or pth for osteoporosis . assuming a maximum metering volume of 200 microliters for 10 actuations , canisters with volumes less than about 6 . 0 ml , including headspace are desirable . in some variations , the total volume of the drug is less than or equal to about 75 % of the total volume of the canister . in other variations , the total volume of the drug is less than or equal to about 50 % of the total volume of the canister .
a metered does inhaler which includes a canister assembly which has a minimal volume canister and primeless valve to reduce waste , minimize total drug contained therein , and increase the reproducibility of dosage delivered .