Step 1: Recall the source of opioids.
Papaver somniferum (opium poppy) yields latex containing alkaloids such as morphine and codeine.
These drugs are collectively called
\[
\boxed{\text{Opioids}.}
\]
Step 2: Eliminate other options.
\[
\begin{aligned}
\text{Cannabinoids} &\rightarrow \textit{Cannabis sativa}
\text{Cocaine} &\rightarrow \textit{Erythroxylum coca}
\text{Dopamine} &\rightarrow \text{Neurotransmitter}
\end{aligned}
\]
Step 3: Choose the correct option.
Hence,
\[
\boxed{(A)}
\]
is the correct answer.