Admob Unity Plugin - Mute interstitial ads

Hey guys I am really hoping for some help on this one. In my game I have a button that once pressed mutes all sound and music. I have monetized my game with Google Admob and I am using the official Admob Unity Plugin. My problem is that when an interstitial is shown it is not muted. I want to mute my ads when my game is muted. Can anyone help me accomplish this?

My script for displaying ads looks like this:

using UnityEngine;
using System.Collections;
using GoogleMobileAds.Api;

public class AdmobScript : MonoBehaviour {

	private static string interstitialId;
	private static InterstitialAd interstitial;
	private static AdRequest interstitialRequest;
	public static int counter;

	void Awake()
	{
		DontDestroyOnLoad(gameObject);
	}
		
	void Start () 
	{
		#if UNITY_ANDROID
		interstitialId = "ca-app-pub-1518441074738585/3382052954";
		#elif UNITY_IPHONE
		interstitialId = "ca-app-pub-1518441074738585/2544448158";
		#else
		interstitialId = "unexpected platform";
		#endif

		counter = 0;
		requestInterstitial ();
	}
	
	public static void requestInterstitial()
	{
		interstitial = new InterstitialAd (interstitialId);
		interstitialRequest = new AdRequest.Builder ().TagForChildDirectedTreatment(true).Build ();
		interstitial.LoadAd (interstitialRequest);
	}

	public static void showInterstitial()
	{
		if (interstitial.IsLoaded()) 
		{
			interstitial.Show ();
		}
	}

	public static bool isAdReady()
	{
		return interstitial.IsLoaded ();
	}
}

It was not possible back then. I don’t know if it is now.