factors to integers preserving value in a dataframe

I want to produce a dataframe with integer columns for elements of  
string pairs:

pairs <- c("10 21","23 45")
pairs.split <- lapply(pairs,function(x)strsplit(x," "))
pdf <- as.data.frame(pairs.split)
names(pdf) <- c("p","q")

-- at this point things look good, except the columns are factors,  
as I didn't change the default stringsAsFactors parameter to the  
as.data.frame.

Now if I want to convert columns to integers, I get

typeof(pdf$p)

[1] "integer"

pdf$p

[1] 10 21
Levels: 10 21

as.integer(pdf$p)

[1] 1 2

-- being factor levels instead of the original values.  I could have  
used stringsAsFactors=F and then convert the strings to integers  
with as.integer all the same; what other ways are there -- e.g., is  
there a way to convert integer-looking factors to integers directly,  
without substituting levels?

Cheers,
Alexy